Southwest Research-Extension Center Field Day 2018

Kansas agricultural research from the Southwest Research-Extension Center.


D. Bond and J. Slattery
In 2017, annual precipitation of 23.45 in. was recorded, which is 5.55 in. above normal. Only five months had above-normal precipitation. May (5.00 in.) was the wettest month, while both April and July recorded greater than 4 in. of precipitation. The largest single amount of precipitation was 2.10 in. on April 30. November and December were the driest months with only a recorded trace of precipitation.
Snowfall for the year totaled 24.7 in.; January, April, and May had 2.7, 16.0, and 6.0 in., respectively, for a total of 9 days of snow cover. The longest consecutive periods of snow cover, 4 days, occurred January 5-8 and April 29-May 2.
Record-high temperatures were recorded on 6 days: February 22 (79°F); March 20 (91°F), 21 (87°F), and 24 (89°F); and November 18 (80°F) and 28 (84°F). A record-high temperature was tied on November 15 (80°F). No record-low temperatures were recorded. A record-low temperature was tied on May 24 (33°F). July was the warmest month with a mean temperature of 76.5°F. The hottest day of the year (103°F) occurred on June 22. The coldest day of the year (-8°F) occurred on January 7. January was the coldest month with a mean temperature of 30.4°F.
Mean air temperature was above normal for 9 months. February had the greatest departure above normal (7.3°F), and August had the greatest departure below normal (-4.6°F). Temperatures were 100°F or higher on 6 days, which is 5 days below normal. Temperatures were 90°F or higher on 52 days, which is 11 days below normal. The latest spring freeze was May 4, which is 2 days earlier than normal; the earliest fall freeze fell on October 10, which is 3 days later than normal. This produced a frost-free period of 159 days, which is 5 days more than the normal of 154 days.
Open-pan evaporation from April through September totaled 59.58 in., which is 11.82 in. below normal. Wind speed for this period averaged 4.1 mph, which is 1.2 mph less than normal.
The 2017 weather information for Tribune is summarized in Table 1.

Introduction
To stabilize crop yields, dryland rotations in western Kansas commonly include fallow to accumulate soil water. Fallow is relatively inefficient at storing and utilizing precipitation when compared to storage and utilization of precipitation received during the growing season. Fallow periods increase soil erosion and organic matter loss (Blanco and Holman, 2012), and represent a large economic cost to producers. Forages are valuable feedstuff to the cow/calf, stocker, cattle feeding, and dairy industries throughout the region (Hinkle et al., 2010). Forages grown in place of fallow can increase precipitation use efficiency, improve soil quality, and increase profitability (Holman et al., 2018). This study tests several forage rotations for water use efficiency, forage quality, yield, and profitability.
Annual forages are grown for a shorter period and require less water than traditional grain crops. Including annual forages into the crop rotation might enable increasing cropping system intensity and opportunistic cropping. "Opportunistic cropping" or "flex cropping" is the planting of a crop when conditions (soil water and precipitation outlook) are favorable and fallowing when unfavorable. Wheat yields following spring annual forages such as oat (O) were similar to wheat yields following fallow in a wheat-fallow rotation in non-drought years, but wheat yields were reduced in drought years (Holman et al., 2012). This indicates the opportunity to intensify the cropping system in favorable years. Forage producers in the region commonly grow continuous winter triticale (T), winter triticale or summer crop silage, or forage sorghum hay (S), but they lack a proven rotation concept for forages such as that developed for grain crops (e.g. winter wheat-summer crop-fallow). Continuous winter triticale often develops winter annual grass problems, while continuous forage sorghum produces lower quality forage than triticale. Producers are interested in identifying forage rotations that increase pest management control options, spread out equipment and labor resources over the year, reduce the impact of variable weather risks, and increase profitability. Growing forages throughout the year greatly reduces the risk of crop failure due to variable precipitation.
Growing winter triticale (T) or forage sorghum (S) double cropped (T/S/T), yielded 30% less than non-double crop yields (T-S-O) (P ≤ 0.05) near Garden City, KS, between 2007 and 2010. Double cropping increased forage production's annual yield 40% more than growing one crop annually (Holman et al., 2012). However, crop establishment was more challenging and crop growth was highly dependent on growing season precipitation in the double-crop rotation compared to annual cropping. Due to the high cropping intensity it was also challenging to implement timely field operations in the double crop system. An intermediate cropping intensity of three crops grown in two years or four crops in three years might be a successful crop rotation in western Kansas.
Recently in western Kansas, glyphosate-resistant kochia (Kochia scoparia) was identified, and several other grasses (e.g. tumble windmill grass and red three-awn) are already tolerant of glyphosate and other herbicides. Although continuous no-till was shown to provide better water conservation and crop yields, this result is contingent upon being able to control weeds with herbicides during fallow. Limited information is available on the effect of occasional strategic tillage to control herbicide tolerant weeds on forage yield. Yield of forage crops following tillage might not be affected as much as in grain crops, since forages require less water. Information is needed on the effects of occasional tillage in forage based cropping systems.

Study Objectives
1. Identify and characterize profitable forage cropping systems. 2. Determine the effect of occasional strategic tillage on forage system yield, profit, and soil health.

Experimental Procedures
An annual forage rotation experiment was initiated in 2012 at the Southwest Research-Extension Center near Garden City, KS. All crop phases were in place by 2013, with the exception of T-S-O, which had all crop phases in place by 2015. The study design was a randomized complete block design with four replications. Treatment was crop phase (with all crop phases present every year) and tillage (no-tillage or min-tillage). Plots were 30-ft wide × 30-ft long. Crop rotations were one-, three-, and four-year rotations (see treatment list below). Crops grown were winter triticale (×Triticosecale Wittm.), forage sorghum (Sorghum bicolor L.), and spring oat (Avena sativa L.). Tillage was implemented after spring oat was harvested in treatments 3 and 5, using a single tillage with a Minimizer (Premier Tillage Mfg.) sweep plow with 6-ft blades and trailing pickers. Year 3: forage sorghum; Year 4: spring oat (single tillage after spring oat, min-tillage): (T/S-S-S-O min-tillage) 6. Year 1: winter triticale; Year 2: forage sorghum; Year 3: spring oat (no-tillage): (T-S-O) Winter triticale was planted at the end of September, spring oat was planted the beginning of March, and forage sorghum was planted the beginning of June. Crops were harvested at early heading to optimize forage yield and quality (Feekes 10.1) (Large 1954). Winter triticale was harvested approximately May 15, spring oat was harvested approximately June 1, and forage sorghum was harvested approximately the end of August. Forage yields were determined from a 3-× 30-ft area cut 3 in. high using a small plot Carter forage harvester from each plot. Forage yield and quality (protein, fiber, and digestibility) were measured at each harvest. Gravimetric soil moisture content was measured at planting and harvest to a depth of 6 ft using 1-ft increments. Precipitation storage efficiency (% of precipitation stored during the fallow period) was quantified for each fallow period, and crop water use efficiency (forage yield divided by soil water used plus precipitation) was determined for each crop harvest. Crop yield response to plant available water (PAW) at planting was used to develop a yield prediction model based on historical or expected weather conditions. Most producers use a soil probe rather than gravimetric sampling to determine soil moisture status, so soil penetration with a Paul Brown soil probe was used four times per plot at planting to estimate soil water availability. Previous studies found a soil moisture probe provided a practical, easy way to determine soil moisture level and crop yield potential. Profitable forage and tillage systems identified in this study will benefit producers in the High Plains region.

Rotation Yield
Annual rotation yield was determined by measuring total yield for the rotation and dividing by the number of years in the rotation. This method allowed for comparing rotations of different years to each other for annual forage production (Table 1 and  Forage yield per crop harvest was determined for each rotation since planting and harvesting expenses are the major expenses to growing a crop; yield and value per ton are the major income components. Crop rotations with greater yield per harvest are likely to be more profitable compared to rotations with low yield per harvest since some of the variable and fixed expenses are less. Although oat and triticale yield less than forage sorghum, they are also higher in crude protein and digestibility and are worth more per unit than forage sorghum. A full economic analysis of rotations will be completed at the conclusion of this study. In 2013, S-S had the greatest yield per harvest, and all other rotations had similar yields per harvest (Table 1 and Figure 2). In 2014, T/S-S-O (no-tillage) had lower average harvest yields than S-S or T/S-S-S-O (min-tillage) but was similar to T/S-S-O (min-tillage) and T/S-S-S-O (no-tillage). In 2015, S-S had the greatest yield per harvest, and T-S-O had the lowest yield per harvest, which was lower than S-S or T/S-S-S-O (no-tillage), but comparable to the other treatments. In 2016 and 2017, S-S had the greatest yield per harvest and T-S-O had the least. Sorghum has the greatest yield potential of the three crops investigated, but S-S does not allow for crop diversification, improved weed management, higher forage quality (oats and triticale), or the ability to reduce weather risk by growing a crop during different times of the year.

Crop Yield
Full-season sorghum yields either grown after T/S or S yielded similarly across rotations ( Figure 3). Double-crop forage sorghum yielded less than full-season forage sorghum, but varied greatly from year to year based on precipitation during the growing season. Double crop forage sorghum yielded 70% less than full-season in 2013, 7% less in 2014, 12% less in 2015, 10% less in 2016, and 38% less in 2017. Across all years, double-crop (5,540 lb/a) averaged 22% less than full-season forage sorghum (7,103 lb/a). The lower yield of double-crop forage sorghum was due to less available soil moisture at planting. Sorghum yield was not affected by tillage or length of rotation, although there was a tendency for no-till forage sorghum yields to be greater than min-till yields.
Triticale yield was not affected by length of rotation but was affected by tillage. Averaged across years, triticale in min-tillage (3,321 lb/a) yielded 160% more than no-tillage (2,067 lb/a). The only tillage in this study occurred in the fallow period before triticale and, in this study, benefited the triticale crop. The exception was in 2017 when no-till (1869 lb/a) yielded more than min-till (1518 lb/a). Other studies and producers have found tillage ahead of a winter wheat crop has minimal impact on yield and can improve weed control, but tillage ahead of grain sorghum often reduced grain yield. For these reasons, tillage was only used ahead of triticale and, similar to winter wheat, did not reduce yields, but actually increased yields in the first 4 years of this study.
Oats failed to make a crop in 2013 due to drought conditions, and yields were similar among rotations in 2014 (400 lb/a), 2015 (4,900 lb/a), 2016 (2,300 lb/a), and 2017 (883 lb/a). Yields in 2015 were higher than other years due to very favorable spring precipitation. Oat yield was not affected by tillage or rotation.

Soil Water
Plant available water at planting was measured to a 6-foot soil depth, and soil water content varied by year and planting period. Soil water was greatest at full-season forage sorghum planting (6.3 in.), and was not different among the other planting periods, ranging from 3.42 to 4.43 in. (Figure 4). Double-crop forage sorghum averaged 4.43 in., which was 1.89 less in. of PAW at planting than full-season forage sorghum.
Water use efficiency (WUE) was greatest in forage sorghum, with full-season producing 628 lb/a/in. and double-crop producing 565 lb/a/in. Water use efficiency for winter triticale averaged 379 lb/a/in., and oat was 297 lb/a/in. The yield potential and thus water use efficiency was greater with forage sorghum than triticale or oat. However, when precipitation was favorable during a particular growing season, such as oat in 2015, the WUE of oat was comparable to forage sorghum. In years with moisture stress, WUE of double-crop forage sorghum was less than full-season, but in favorable moisture years WUE of double-crop was greater than full-season ( Figure 5).
Precipitation storage efficiency (PSE) varied by fallow period and ranged from 14% ahead of winter triticale to 39% for double-cropped forage sorghum. Precipitation storage ahead of full-season forage sorghum was 37% and ahead of oat planting was 31% ( Figure 6).     Estimating Annual Forage Yields with Introduction Annual forage crops are grown for a shorter time and require less moisture than traditional grain crops. Including annual forages in the cropping system might enable increased cropping intensity and opportunistic cropping. "Opportunistic cropping," or "flex cropping," is the planting of a crop when conditions (soil water and precipitation outlook) are favorable and fallowing when unfavorable. Forage producers in the region commonly grow winter triticale, forage sorghum, or spring triticale/oat. Producers are interested in forage crop rotations that enable increased pest management control options, spread out equipment and labor resources over the year, reduce weather risk, and increase profitability. Growing forages throughout the year greatly reduces the risk of crop failure. Understanding the yield relationship to PAW and GSP would help producers better meet their forage needs.

Study Objectives
1. Quantify yield relationship of winter, spring, and summer forages with PAW and GSP. 2. Determine water use efficiency of winter, spring, and summer forages.

Experimental Procedures
Annual forages were grown as part of several different rotation experiments near Garden City, KS. Plant available water, growing season precipitation, and forage yield were measured annually. Data for winter triticale and forage sorghum were available from 2008 through 2017, and spring triticale from 2012 through 2017.
Annually, winter triticale was planted at the end of September, spring triticale was planted at the beginning of March, and forage sorghum was planted at the beginning of June. Crops were harvested at early heading to optimize forage yield and quality (Feekes 10.1) (Large 1954). Annually, winter triticale was harvested approximately May 15, spring oat was harvested approximately June 1, and forage sorghum was harvested approximately the end of August. Forage yields were determined from a 3-× 30-ft area cut 3 in. high using a small plot Carter forage harvester for each plot. Forage yield was measured at each harvest. Gravimetric soil moisture content was measured at planting and harvest to a depth of 6 ft using 1-ft increments. Precipitation storage efficiency (percent of precipitation stored during the fallow period) was quantified for each fallow period, and crop water use efficiency (forage yield divided by soil water used plus precipitation) was determined for each crop harvest. Crop yield response to plant available water at planting was regressed to estimate yield. These yield data will eventually be used to develop a yield prediction model based on historical or expected weather conditions when sufficient years of data are obtained.
Data produced by this study will be used to evaluate the economics of forage rotations and tillage. Production costs and returns will be calculated using typical values for the region. The implication of using forages on crop insurance dynamics and risk exposure is a critical component of a producer's decision-making process and will be evaluated at the conclusion of this study.

Winter Triticale
Winter triticale forage yield was correlated to PAW and GSP, although yield response was highly variable. Plant available water explained approximately 13% and GSP explained 5% of the variability in forage yield (Figures 1 and 2). Together, PAW and GSP explained 48% of the variability in forage yield ( Figure 3). For every inch of water used (soil water plus GSP), yield was increased 640 lb/a. Averaged across the study period, yield was 3,500 lb/a.

Spring Triticale
Spring triticale forage yield was significantly correlated to PAW and GSP, but yield response was highly variable. Plant available water and GSP both explained approximately 5% of the variability in forage yield independently (Figures 4 and 5). Combining PAW and GSP explained only 10% of the yield variability; suggesting something other than moisture, most likely temperature greatly impacts yield ( Figure 6). For every inch of water used (soil water plus GSP), yield was increased 187 lb/a. Averaged across the study period, yield was 1,450 lb/a.

Forage Sorghum
Forage sorghum forage yield was correlated to PAW but not GSP, and yield response was variable. Plant available water explained approximately 22% and GSP explained 3% of the variability in forage yield (Figures 7 and 8). Together, PAW and GSP explained 23% of the variability in forage yield ( Figure 9). For every inch of water used (soil water plus GSP), yield was increased 410 lb/a. Averaged across the study period, yield was 5,400 lb/a.  Figure 9. Forage sorghum yield response to water use (soil water plus growing season precipitation) and average yield (bold line) across the study period.
Integrated Grain and Forage Rotations J. Holman, A. Obour, T. Roberts, and S. Maxwell Summary Producers are interested in growing forages in rotation with grain crops. Many producers are interested in diversifying their operations to include livestock or grow feed for the livestock industry. By integrating forages into the cropping system, producers can take advantage of more markets and reduce market risk. Forages require less water to make a crop than grain crops, so the potential may exist to reduce fallow by including forages in the crop rotation. Reducing fallow through intensified grain/forage rotations may increase profitability and sustainability compared to existing crop rotations.
This study was started in 2013, with crops grown in-phase beginning in 2014. Grain crops were more sensitive to moisture stress than forage crops. Growing a double-crop forage sorghum after wheat reduced grain sorghum yield the second year, but never reduced second-year forage sorghum yield in the years of this study. If double-crop forage sorghum is profitable, it appears the cropping system can be intensified by growing second-year forage sorghum. Since other research has found cropping intensity should be reduced in dry years, caution should be used when planting double-crop forage sorghum by evaluating the soil moisture conditions and precipitation outlook. The "flex-fallow" concept could be used to make a decision on whether to plant double-crop forage sorghum to increase the chance of improving cropping system profitability. Importantly, this research showed forages are more tolerant to moisture stress than grain crops and the potential exists to increase cropping intensity by integrating forages into the rotation.

Introduction
Interest in growing forages and reducing fallow has necessitated research on soil, water, and crop yields in intensified grain/forage rotations. Fallow stores moisture, which helps stabilize crop yields and reduces the risk of crop failure; however, only 25 to 30% of the precipitation received during the fallow period of a no-till wheat-sorghum-fallow rotation is stored. The remaining 75-70% precipitation is lost, primarily due to evaporation. Moisture storage in fallow is more efficient earlier in the fallow period, when the soil is dry, and during the winter months when the evaporation rate is lower. It may be possible to increase cropping intensity without reducing crop yields by using forage crops in the rotation. This study evaluated integrated grain/forage rotations compared to traditional grain-only crop rotations.

Experimental Procedures
A study beginning in 2013 evaluated various integrated grain and forage rotations compared to a no-till wheat-grain sorghum-fallow rotation. All phases of the rotation were present every year and in-phase by 2014. A total of 11 crop rotations were evaluated. Beginning in 2013, the wheat/forage sorghum-grain sorghum-oat rotation was replaced with a wheat/forage sorghum-grain sorghum-fallow rotation since the no-fallow rotation tended to be too intensively cropped during dry years. The study design was a split-plot randomized complete block design with four replications; crop phase (wheat-sorghum-fallow) was the main plot and alternative crop choices were the splitplot. Each split-plot was 30-ft wide and 120-ft long.
"Flex-fallow" is a spring planting decision based on current soil moisture condition and seasonal outlook. Spring oats were planted when 14 inches or more of plant available water (PAW) was determined available by using a Paul Brown moisture probe, and seasonal precipitation forecasted outlook was neutral or favorable; otherwise the treatment was left fallow. The flex-fallow treatment was intended to take advantage of growing a crop during the fallow period in wet years and fallowing in dry years. A flex-fallow crop was planted in 2013 and 2016, but not in 2014, 2015, 2017, or 2018.
Each year, winter triticale was planted approximately October 1. Spring crops were planted as early as soil conditions allowed, ranging from the end of February through the middle of March. Spring forage crops were harvested approximately June 1. Forage sorghum was either planted around June 1st for full-season or following wheat harvest around July 1st for double-crop. Forage biomass yields were determined from a 3-× 120-ft area cut 3 in. high using a small plot Carter forage harvester. Winter wheat and grain sorghum were harvested with a small plot Wintersteiger combine from a 6.5-× 120-ft area at grain maturity.
Volumetric soil moisture content was measured at planting and harvest of winter wheat, grain sorghum, forage sorghum, spring oat, or fallow using a Giddings soil probe by 1-ft increments to a 6-ft soil depth. In addition, volumetric soil content was measured in the 0-3 in. soil depth at wheat planting to quantify moisture in the seed planting depth. Grain yield was corrected for moisture content, and test weight was measured using a grain analysis computer (GAC 2100, Dickey-John). Seed weight was determined from a 1,000-seed count using a seed counter computer (801, Seedburo). Grain samples were analyzed for nitrogen content.

Winter Wheat
Winter wheat yield, plant available moisture at planting, water use efficiency, and precipitation storage efficiency prior to planting were not affected by whether forage sorghum or grain sorghum were grown in place of one another in the rotation (Table 2). Wheat yields were reduced when oat was grown in place of fallow. Previous research found growing oats in place of fallow reduced wheat yields when wheat yield potential was less than 50 bu/a. A flex-crop was grown in 2013 and 2016, but not 2014, 2015, 2017, or 2018. Dry conditions developed soon after planting a flex-crop in 2013, and growing a flex-crop in place of fallow reduced wheat yield 67% in 2014 and did not affect 2017 yield. Dry fall conditions and rabbit feeding killed the wheat crop in 2016 and there was no yield that year. Soil moisture was dry in the fall of 2017 and some of the wheat did not emerge until spring. Conditions were again very dry during the winter and spring of 2018.

Grain Sorghum
Grain sorghum yield was highly correlated with plant available moisture at planting, which explained 47% of the variability in grain yield (Figure 1). Approximately 8 bushels were grown for every acre-inch of plant available water at planting. Plant available moisture was highest when forage sorghum was not double-cropped between wheat and grain sorghum (Table 3) and tended to be higher when nothing was grown in the fallow phase ahead of winter wheat. Higher wheat yields and residue levels improved the WUE of grain sorghum. Growing double-crop forage sorghum ahead of grain sorghum reduced grain sorghum yield 61% in 2014, 38% in 2015, 20% in 2016, and 56% in 2017. Growing a forage sorghum crop after wheat reduced the amount of plant available water at planting and water use efficiency of the subsequent grain sorghum crop each year, but did not affect precipitation storage efficiency in the fallow period ahead of grain sorghum. Growing a forage sorghum crop reduced the test weight and seed weight of grain sorghum in 2015 and seed weight in 2017.

Forage Sorghum
Forage sorghum yield was also correlated with plant available moisture at planting, but not as much as grain sorghum. Plant available moisture at planting explained approximately 33% of the variability in forage yield ( Figure 2). Approximately 480 lb of forage was grown for every inch of plant available water (PAW) at planting.
Forage sorghum yields were not different across treatments in 2014, except double-crop FS in winter wheat/forage sorghum-forage sorghum-spring oat (ww/FS-fs-o) yielded 2,200 lb/a less than full-season forage sorghum in the same rotation of winter wheat/ forage sorghum-forage sorghum-spring oat (ww/fs-FS-o) ( Table 4). This lower yield was most likely due to less plant available water at planting, 1.3 versus 2.1 inches. In 2014, plant available water averaged 1.0 inch ahead of double-crop forage sorghum and 4.1 inches ahead of full season forage sorghum. In 2014 most of the annual precipitation occurred later in the year (June-September), which likely helped improve the yield of double-crop forage sorghum relative to full-season forage sorghum. In 2014, double-crop forage sorghum yielded, on average, 17% less than full-season forage sorghum (3,300 versus 3,900 lb/a). In 2015, most of the precipitation occurred earlier in the year (May-August) than 2014, which helped increase wheat yields but also resulted in comparatively less moisture at planting time of double-crop forage sorghum, 1.6 versus 7.2 inches. As a result, in 2015 double-crop forage sorghum yields were reduced 70% compared to full-season forage sorghum (2,400 versus 8,000 lb/a). In 2016, moisture conditions were favorable during the growing season (June-August), resulting in good forage yields across all treatments. There were 0.8 inches more PAW at planting of the full-season compared to double-crop forage sorghum. Double crop yields were reduced on average 43% compared to full-season forage sorghum (3,900 vs. 6,900 lb/a). In 2017, most of the precipitation occurred during the spring of the year, which increased moisture storage during the fallow period but little moisture during the growing season, resulting in low yields in the double-crop forage sorghum crop. Full season forage sorghum averaged 6,700 lb/a and double-crop averaged 1,000 lb/a. Surprisingly, second-year forage sorghum yields following double-crop forage sorghum were similar to full-season forage sorghum following wheat with fallow between wheat harvest and sorghum planting (Table 4). Yet forage sorghum planted after double-crop forage sorghum had an average of 3 inches less soil moisture compared to forage sorghum planted after wheat with a fallow period between crops. In dry years this difference in plant available soil water may result in yield differences, but it did not affect yield in this study. The yield plateau of a forage crop is lower than a grain crop, which might explain why there was no yield penalty for second-year forage sorghum grown after either fallow or double-crop forage sorghum. These results suggest that as long as the benefits of growing a double-crop forage sorghum crop exceeded costs, an extra forage sorghum crop could be grown in the rotation. A partial enterprise analysis of this phase of the rotation only, indicated double-crop forage sorghum yield needs to be at least 30% of full-season forage sorghum, or at least 2,000 lb/a, for a double-crop forage sorghum crop that is grazed to be profitable. The additional variable expenses of growing double-crop forage sorghum would be around $25.00/a.

Spring Oat
Spring oat yield was not affected by rotation treatment and yielded 564 lb/a in 2014, 1,927 lb/a in 2015, 1,877 lb/a in 2016, and 1456 lb/a in 2017.

Conclusions
Wheat and spring oat yields were not affected whether grain or forage sorghum were grown in place of each other in the crop rotation. Oats were grown in place of fallow in those years that indicated favorable moisture conditions. Wheat yields were reduced when oats were grown in place of fallow. Our previous fallow replacement research found wheat yield potential needed to be greater than 50 bushels for wheat yields to not be reduced by growing a crop in place of fallow. Wheat yield potential was very low in all years at 6 bu/a in 2014, 15 bu/a in 2015, failed to make grain in 2016, and 8 bu/a in 2017.
Grain sorghum yield was more sensitive to moisture stress than forage sorghum. Growing a double-crop forage sorghum after wheat reduced grain yield 20 to 60% the second year but never reduced forage sorghum yield in the years of this study. However, in low precipitation years, full-season forage sorghum yields might be more negatively impacted than they were in this study. Double-crop forage sorghum yields were more sensitive than full-season forage sorghum. Double-crop forage sorghum yields averaged 47% less than full-season, and in the driest growing season (2017) yields were reduced 85%. As long as double-crop forage sorghum is profitable, which we identified to be around 2,000 lb/a yield when grazed, it appears the cropping system can be intensified without negatively affecting second-year forage sorghum yield. Caution should be used when planting double-crop forage sorghum, by evaluating soil moisture condition and precipitation outlook, since other research has found cropping intensity should be reduced in dry years. The "flex-fallow" concept could be used to make a decision on whether or not to plant double-crop forage sorghum to increase the chance of success. Importantly, this research showed forages are more tolerant to moisture stress than grain crops, and the potential exists to increase cropping intensity by integrating forages into the rotation. Wheat-grain sorghum-flex-fallow ww-gs-fx 2 Wheat-grain sorghum-fallow ww-gs-fl 3 Wheat/forage sorghum-forage sorghum-oat ww/fs-fs-o 4 Wheat-forage sorghum-oat ww-fs-o 5 † Wheat/forage sorghum-grain sorghum-oat ww/fs-gs-o 6 Wheat-grain sorghum-oat ww-gs-o 7 Wheat-forage sorghum-oat (tilled) ww-fs-o(T) 8 Wheat-forage sorghum-fallow ww-fs-fl 9 Wheat-forage sorghum-flex-fallow ww-fs-fx 10 Wheat/forage sorghum-forage sorghum-flex-fallow ww/fs-fs-fx 11 Wheat/forage sorghum-grain sorghum-flex-fallow ww/fs-gs-fx 12 Wheat/forage sorghum-grain sorghum-fallow ww/fs-gs-fl

Summary
During the past several years, applying fungicide to wheat has become a more common practice. The availability of cost-effective generic fungicides, as well as the positive yield responses often reported, seem to be the potential drivers for the adoption of such practices by producers. A wheat fungicide trial was conducted in Garden City, KS, to answer the following questions: 1) Are fungicide applications profitable? and 2) Can remote sensing technology be used to quantify the efficacy of different fungicide products? The study consisted of two wheat varieties sown on September 30, 2016 (Oakley CL, highly resistant to stripe rust; and TAM 111, highly susceptible to stripe rust) and treated with different fungicide products. Stripe and leaf rust were the major fungal diseases impacting wheat yield in southwest Kansas in 2017. Wheat production in 2017 was impacted by dry planting conditions in late 2016, a winter ice storm in January, and a late snow storm on April 30, and severe wheat streak mosaic virus infestation. There were significant differences in grain yield among fungicide products for both TAM 111 and Oakley CL. The large changes in normalized difference vegetation index (NDVI) values suggest that multiple environmental factors were interacting to impact the wheat plant health. The benefit of fungicide application observed on yield was minimal under the environmental conditions of 2017.

Introduction
In recent years, producers are becoming interested in protecting wheat grain yield from major fungal diseases due to the availability of more affordable generic fungicides. However, it is important for producers to be aware that application of fungicides protects yield potential that is present at the time of application. Fungicides serve as yield protectors by enhancing the plant health. Therefore, it is common for producers to often associate delayed harvest with fungicide application. Fungicides allow plants to stay green and maintain their leaves longer, using more nutrients during the late development stages.
Previous research has reported variable results regarding the value of fungicide application in the Great Plains. In Kansas, several years of research have indicated that a single fungicide application to a susceptible variety, on average, could provide a 10% yield increase, relative to the untreated control (De Wolf, 2013). To maximize the benefit of a fungicide application, producers should know the vulnerability of the variety to be treated. Susceptible varieties are more likely to benefit from foliar fungicides as compared to varieties with moderate to high levels of resistance. It is also important to pay attention to weather conditions and scouting reports within a field, region, and even surrounding states to the south.
Rating the effectiveness of a foliar fungicide application on disease control is often tedious and very subjective. With the onset of remote sensing technology, there are great opportunities to develop more objective approaches for rating varietal resistance to diseases and the efficacy of fungicides. Measurements such as the normalized difference vegetative index (NDVI)-which combines wavebands in the red region of the spectrum that is controlled by the leaf pigment content, and wavebands in the near-infrared region of the spectrum that is controlled by the internal leaf structures-are strongly correlated with plant health. Application of fungicide is reported to enhance plant health that results in the plant staying green longer. Therefore, differences in NDVI before and after fungicide application relative to the control could be used to develop a more objective scale for rating fungicide efficacy.
The objectives of this study were to evaluate the value of variety selection and application of a foliar fungicide as part of an economically optimal disease management plan and to assess the potential for using remote sensing measurements such as NDVI as a tool for rating fungicide efficacy.

Experimental Procedures
An experiment was established at the Southwest Research-Extension Center in Garden City, KS, in fall 2016. The design of the experiment was a randomized complete block design with three replications consisting of eleven fungicide application treatments and two wheat varieties: Oakley CL (highly resistant to stripe rust) and TAM 111 (highly susceptible to stripe rust). The experimental treatments are summarized in Table 1. Experimental plots were sown on September 30, 2016, at a seeding rate of 120 lb/a, and were 7.5-ft wide × 30-ft long. The entire experimental area was fertilized with 100 lb of N/a at green-up in March of 2017, and plots were sprayed with a mixture of 0.4 pints of Starane, 0.375 quarts of MCPA, and 0.1 oz of Ally the first week of April for weed control. Fungicides were applied at a volume of 15 GPA with a CO 2 backpack sprayer when the flag leaf fully emerged and the ligule was visible (Feekes GS 9). A plot combine 7.5-ft wide was used to harvest 25 ft from each plot for yield. A subsample was collected from each plot to determine the test weight and moisture content. The yield was adjusted to 13% moisture.
NDVI was collected before and 15 and 30 days after the flag leaf fungicide application. A handheld Greenseeker sensor (Ntech Industries, Inc, Ukiah, CA) was used to measure the NDVI. The difference between the before and after NDVI values were used to assess the efficacy of the fungicide. The smaller the difference between the before and after application NDVI values of the treated compared to the control was indicative of the efficacy of the fungicide.

Results and Discussion
The 2017 wheat crop overcame many challenges, including a late winter snowstorm that covered the wheat in more than 20 inches of snow for three days, mild leaf and stripe rust, wetter than normal conditions in March and April, and warmer temperatures were the main environmental conditions for the 2016-2017 wheat crop.
The results of this study showed that the effect of fungicide on yield differed significantly among products and across both resistant and susceptible varieties. The variability in response to the fungicide applications may be attributed to the impact of environmental stress on wheat as well as the later application of the fungicide at Feekes 10 compared to Feekes 9 in 2016. Compared to the results of 2016, TAM 111 (the susceptible variety) once again out-yielded the resistant variety Oakley CL. Similar to 2016, lodging was again a problem for the Oakley CL variety (Table 3). The generic fungicide was the most consistent in producing a net return, with a net benefit of $3.45 for TAM 111 and $9.64 for Oakley CL. Oakley CL is not resistant to leaf rust, so a mild infestation of this fungus likely justified justifying the greater net returns as compared to TAM 111.
In 2016, Foster et al. (2017) reported differences of 0.07 in NDVI 30 days after application in the check TAM 111 plot, but in 2017 differences in NDVI for the check TAM 111 plot were 0.07 15 days after application, and 0.32 30 days after application (Table  3). Contrary to 2016, the changes in NDVI indicated significant differences in efficacy among the different fungicides 15 and 30 days after application for both TAM 111 and Oakley CL. The large changes in NDVI and the significant difference in efficacy among the fungicides in 2017 may be attributed to the later application timing, the impact of the April 30 snowstorm, other diseases (mild infestation of leaf rust), lodging, warmer temperatures in May and June, and the effect of the crop approaching physiological maturity at the time of the 30 day NDVI sampling.

Conclusion
The results of 2017 demonstrate the complexity of environmental conditions on wheat management. Therefore, it is important for producers to manage each crop independently, taking into consideration the environmental condition of that year in making decisions on fungicide application. Scouting the crop and gathering information about the condition of the crop is vital to making an optimal decision. Clearly, in 2017 the challenge of getting fungicide applied on time was a factor. In these situations, a good decision is to go with the generic products to minimize the potential for economic losses. The results observed in 2017 in no way should be interpreted outside of context of the particular growing season from which data were collected-that is, without considering the environmental conditions under which the wheat was grown. Fungicide decisions should take into consideration the current crop growing condition and yield potential, inoculum present in the field or neighboring fields, and weather conditions during that particular growing season. Remote sensing technology shows potential in quantifying the efficacy of different fungicides. However, the result was most beneficial when compared to the control, which might offer some challenges in real-world application.

Chemical Disclaimer
Fungicide pricing used in this report maybe higher or lower. Brand names appearing in this report are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Person using such products assume responsibility for their use in accordance with current label directions of the manufacturer.    Treatments  TAM OAK  TAM OAK  TAM OAK  TAM OAK  TAM

Summary
Producers are interested in growing cover crops and reducing fallow. Growing a crop during the fallow period would increase profitability if crop benefits exceeded expenses. Benefits of growing a cover crop were shown in high rainfall areas, but limited information is available on growing cover crops in place of fallow in the semiarid Great Plains.
A study was conducted from 2007-2018 that evaluated cover crops, annual forages, and short season grain crops grown in place of fallow. In the first experiment (2007)(2008)(2009)(2010)(2011)(2012), the rotation was no-till wheat-fallow. The second experiment (2012-2018) rotation was no-till wheat-grain sorghum-fallow. This report presents results from the second experiment. Wheat yield was affected by growing a crop in place of fallow, but managing the crop as either cover or hay did not affect wheat yield. Wheat yield following the previous crop was dependent on precipitation during fallow and the growing season. In dry years growing a crop during fallow reduced wheat yields, while growing a crop during fallow had little impact on wheat yield in wet years. Grain sorghum yield was only reduced one year by growing a crop in place of fallow, other years there was no yield difference. The length of the fallow period affected subsequent wheat yield. Growing a cover or hay crop in place of fallow had a less negative impact on wheat yield compared to growing a spring grain crop due to a shorter fallow period. Cover crops did not improve wheat or grain sorghum yields compared to fallow. To be successful, the benefits of growing a cover crop during the fallow period must be greater than the expense of growing it; and must compensate for any negative yield impacts on the subsequent crop. Cover crops always resulted in less profit than fallow, while annual forages often increased profit compared to fallow. The negative effects on wheat yields might be minimized with flex-fallow, which is the concept of only growing a crop in place of fallow in years when soil moisture at planting and precipitation outlook are favorable at the time of making the decision to plant.

Introduction
Interest in replacing fallow with a cash crop or cover crop has necessitated research on soil, water, and wheat yields following a shortened fallow period. Fallow stores moisture, which helps stabilize crop yields and reduces the risk of crop failure; however, only 25 to 30% of the precipitation received during the fallow period of a no-till wheat-fallow rotation is stored. The remaining 75 to 70% of precipitation is lost, primarily due to evaporation. Moisture storage in fallow is more efficient earlier in the fallow period, when the soil is dry, and during the winter months when the evaporation rate is lower. It may be possible to increase cropping intensity without reducing winter wheat yield. This study evaluated replacing part of the fallow period with a cover, annual forage, or short-season grain crop. Plant available water at wheat and grain sorghum planting and winter wheat and grain sorghum yields were measured.

Experimental Procedures
A study from 2007-2014 evaluated cover crops, annual forages, and spring grain crops (peas, oat, or triticale) grown in place of fallow in a no-till wheat-fallow rotation. This first experiment was modified beginning in 2012 to a wheat-grain sorghum-fallow rotation. Treatments that stayed the same between experiments 1 and 2 were maintained in the same plots so that long-term treatment impacts could be determined. Fallow replacement crops (cover crop, annual forage, or short-season grain crop) were either grown as standing cover, harvested for forage (annual forage crop), or harvested for grain.
In ). Crops were grown in monoculture and in two-species mixtures of each legume plus triticale. Crops grown for grain were grown in monoculture only. Winter lentil was grown in place of yellow sweet clover beginning in 2008. Crops grown in place of fallow were compared with a wheat-fallow and continuous wheat rotation for a total of 16 treatments. The study design was a split-split-plot randomized complete block design with four replications; crop phase (wheat-fallow) was the main plot, fallow replacement was the split-plot, and fallow replacement method (forage, grain, or cover) was the split-split-plot. The main plot was 480-ft wide × 120-ft long, the split-plot was 30-ft wide × 120-ft long, and the split-split plot was 15-ft wide × 120-ft long.
In experiment 2 (2012-2018) spring crops were grown the year following grain sorghum. Grain sorghum is harvested late in the year and most years do not allow growing a winter crop during the fallow period. Spring planted treatments included spring grain pea, spring pea plus spring oat (Avena sativa L.), spring pea plus spring triticale, spring oat, spring triticale, and a six species "cocktail" mixture of spring oat, spring triticale, spring pea, buckwheat var. Mancan (Fagopyrum esculentum Moench), purple top turnip (Brassica campestris L.), and forage radish (Raphanus sativus L.). In addition, spring grain pea, spring oat, and safflower (Carthamus tinctorius L.) were grown for grain. Safflower was only grown in 2012, and that treatment was replaced with spring oat grown for grain beginning in 2013. Additional treatments initiated in 2013 were yellow sweet clover planted with grain sorghum and allowed to grow into the fallow year, daikon radish (Brassica rapa L.) planted with winter wheat in a wheat-grain sorghum-fallow rotation, shogoin turnip (Raphanus sativus L.) planted with winter wheat in a wheatgrain sorghum-fallow rotation, and spring oats or a cocktail planted in a "flex-fallow" system (Table 1). The flex-fallow treatment was planted when a minimum of 12 inches of PAW (2013 and 2016) was determined using a Paul Brown moisture probe at spring planting; otherwise, the treatment was left fallow. The flex-fallow treatment was intended to take advantage of growing a crop during the fallow period in wet years and fallowing in dry years. Crops grown for grain were grain peas, spring oat, and triticale. Crops grown in place of fallow were compared with a wheat-grain sorghum-fallow rotation for a total of 16 treatments (Table 1). The study design was a split-split-plot randomized complete block design with four replications; crop phase (wheat-grain sorghum-fallow) was the main plot, fallow replacement was the split-plot, and fallow replacement method (forage, grain, or cover) was the split-split-plot. The main plot was 330-ft wide × 120-ft long, the split-plot was 30-ft wide × 120-ft long, and the split-split plot was 15-ft wide × 120-ft long.
Annually, winter wheat was planted on approximately October 1. Spring crops were planted as early as soil conditions allowed, ranging from the end of February through the middle of March. Spring cover and forage crops were chemically terminated or forage-harvested approximately June 1 at early heading (Feekes 10.1) (Large, 1954). Biomass yields for both cover crops and forage crops were determined from a 3-× 120-ft area cut 3 in. high using a small plot Carter forage harvester from within the split-splitplot managed for forage. Winter and spring grain peas and winter wheat were harvested with a small plot Wintersteiger combine from a 6.5-× 120-ft area at grain maturity, which occurred approximately the first week of July.
Volumetric soil moisture content was measured at planting and harvest of winter wheat, grain sorghum, and fallow using a Giddings soil probe by 1-ft increments to a 6-ft soil depth. In addition, volumetric soil content was measured in the 0-3-in. soil depth at wheat planting to quantify moisture in the seed planting depth. Grain yield was adjusted to 13.5% moisture content, and test weight was measured using a grain analysis computer. Grain samples were analyzed for nitrogen content.

Fallow and Growing Season Precipitation
Fallow and growing season precipitation varied greatly during the course of this study (Table 2). Historical 30-yr (1984-2014) average precipitation during the fallow period between grain sorghum harvest and wheat planting (November-December plus January-September) was 18.03 in., and precipitation during the fallow period between wheat harvest and grain sorghum planting (July-December plus January-May) was 16.12 in. Long-term average growing-season precipitation for wheat (October-June) averaged 12.51 in., and growing-season precipitation for grain sorghum (June-October) averaged 11.06 in. Precipitation during the fallow period ahead of wheat planting was below normal Precipitation storage efficiency averaged 28% with cover and 22% with hay, and stored soil water in the 0-6-ft profile averaged 3.5 inches with cover and 2.8 in. with hay at wheat planting. Plant-available soil water in the top 0-3-in. soil depth was not different between cover and hay treatments. Although more soil water tended to be available in the profile following cover crops compared to hay crops, this effect was not large enough to affect wheat yields. The greater average plant-available soil water and precipitation storage with cover crop is likely due to more surface residue in the cover crop treatments compared with hay treatments, which likely helps reduce water runoff and evaporation near the soil surface.

Winter Wheat Yield in Wheat-Grain Sorghum-Fallow
In 2013, 6.25 inches of precipitation occurred during the winter wheat growing season between planting and harvest. This was 50% of normal (12.5 inches) for this time period, and was the third consecutive year of drought. Below-normal precipitation during fallow and the winter wheat growing season resulted in any treatment other than fallow significantly reducing wheat yield 50% or more. The cover crop cocktail treatment yielded 79% less than fallow. Wheat following fallow yielded 19 bu/a and all other treatments yielded between 3 to 9 bu/a ( Figure 1).
In 2014, 14.57 inches of precipitation occurred during the winter wheat growing season between planting and harvest. This was above average, but most of the rain came in June (10.5 inches), which was too late to benefit the wheat crop. Therefore, wheat yields were significantly reduced by 40-80% by any treatment other than fallow, and fallow only yielded 6 bu/a ( Figure 2).
In 2015, 12.18 inches of precipitation occurred during the winter wheat growing season between planting and harvest, with most of this occurring in May (6.38 inches). Were it not for the rainfall received in May, yields likely would have been less than 10 bu/a in fallow. Precipitation received in the previous fallow period (between grain sorghum harvest and wheat planting) from November 2014 to October 2015 was 18.87 inches and the 30-yr average for this period was 18.03 in. The early season moisture stress and late season precipitation minimized yield differences between treatments and fallow ( Figure 3). Only oats for grain, oat, and pea/triticale yielded less than fallow (15 bu/a).
In 2016, a large infestation of rabbits and feeding damage resulted in a failed crop and no grain production.
In 2017, 11.09 inches of precipitation occurred during the winter wheat growing season between planting and harvest. Most of the precipitation occurred in the spring of 2017 and soil conditions were dry at planting through winter. Precipitation received in the previous fallow period (between grain sorghum harvest and wheat planting) from November 2013 to October 2015 was 18.69. The early season moisture stress reduced yield potential and all treatments yielded less than 16 bu/a ( Figure 4). Spring grain treatments yielded (16 bu/a) more than fallow (8 bu/a), which might have been due to more residue from the grain treatments improving water use efficiency.

Grain Sorghum Yield in Wheat-Grain Sorghum-Fallow
The first grain sorghum crop grown in-phase following cover crop treatments was in 2015. The above normal rainfall in 2015, particularly early in the growing season (5.36 inches in July and 3.24 inches in August), resulted in above normal sorghum yields, ranging from 84-109 bu/a ( Figure 5). Despite the above-normal rainfall and yields, there was still a correlation with 2015 grain sorghum and 2014 winter wheat yields; thus, the impact of growing a cover crop was evident two years later.
In 2016, sorghum yield was similar among treatments. The difference in sorghum yield response to treatment between years was likely due to greater wheat yields and more residue following the 2015 wheat crop compared to the 2014 wheat crop. The poor wheat crop in 2014 resulted in low soil residue cover, and the effect of this was shown by differences in sorghum water use efficiency (WUE) among treatments in 2015. In 2016, there were no differences in sorghum yield or WUE across treatments. Additionally, sufficient precipitation during the preceding fallow period and growing season resulted in an average sorghum yield of 63 bu/a, which helped negate any antecedent differences in soil water.
Grain sorghum in 2017 was affected by previous cover crop treatments in 2015. Wheat yields were too low to harvest in 2016, so no comparisons could be made between 2017 grain sorghum and 2016 wheat yields. However, grain sorghum WUE in 2017 matched closely to grain yields. The results in 2017 suggest a similar response to grain sorghum in 2015, that those wheat plots that grew more biomass (data not available) improved grain sorghum WUE and yield ( Figure 6). Fallow yield was similar to the other treatments, while pea (grain) yielded less than oat/triticale/pea, triticale (grain), cocktail, oat/triticale, and oat (grain). The lower yield following pea (grain) was most likely due to more weeds present in that treatment.

Cover vs. Annual Forage
Similar to the first experiment, there was no difference in wheat or grain sorghum yields whether the previous crop was left as cover or harvested for forage, despite slightly more plant available water following cover than forage harvest. This indicates the previous crop can be harvested for forage rather than left standing as a cover crop without negatively affecting wheat or grain sorghum yields.

Conclusions
Fallow helps stabilize crop yields in dry years. Annual precipitation in this study ranged from 12.1 to 23.3 inches. The 30-year average precipitation was 19.24 inches. In dry years, growing a crop during the fallow period reduced wheat yields, but previous research showed that in wet years, growing a crop during the fallow period had little impact on wheat yield. The length of the fallow period also affected yields of the following wheat crop. Growing a cover or hay crop until June 1 affected wheat less than if spring grain crops were grown in place of fallow until July 1. When wheat yields were very low there was a carryover effect onto grain sorghum, reducing WUE and grain yield.
Forages can be profitable to grow in place of fallow in favorable moisture years. However, cover crops were always an expense to grow. The cropping system can be intensified by replacing part of the fallow period with annual forages to increase profit and improve soil quality; however, in semiarid environments, wheat yields will be reduced in years with below-normal precipitation. Across all years (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018) there was a tendency for wheat yields to not be affected by growing a crop in place of fallow when wheat yield potential was 50 bu/a or greater. The negative effect on yield was greater when wheat yield potential was least and the drought period lasted for more than a year. Some of the reduction in grain yield can be offset by growing a cover crop for forage or grain. Negative impacts on grain yields might also be minimized over time with "flex-fallow." Flex-fallow is the concept of only planting a crop in place of fallow when soil moisture levels and precipitation outlook are favorable. Under drought conditions such as 2011-2014, using flex-fallow, a crop would not have been grown in place of fallow. Therefore, flex-fallow may help reduce the negative effects of reduced fallow. Conversely, flex-fallow will not prevent reduced yield in years when growing-season precipitation levels are below normal. Additional years of data are required to determine the feasibility of flex-fallow and the effects of replacing fallow in a wheat-summer crop-fallow rotation.
Oat, triticale, pea, buckwheat, forage brassica, and forage radish. † † Flex: Plant when soil moisture is 14 in. (12 in. in 2013) or > and precipitation outlook is neutral or favorable.     and corn-winter wheat [C-W]). In 2017, corn yields were greatest in the corn-wheat rotation and least with continuous corn. Grain sorghum yields were greater following sorghum than following corn. The wheat was destroyed by a severe infestation of wheat streak mosaic virus and not harvested.

Experimental Procedures
A crop rotation study under sprinkler irrigation at the Kansas State University Southwest Research-Extension Center near Tribune, KS, was initiated in the spring of 2012. The study evaluates four different crop rotations with a limited irrigation allocation. The rotations include 1-and 2-year rotations. The crop rotations are 1) continuous corn; 2) corn-winter wheat; 3) corn-grain sorghum; and 4) continuous grain sorghum (a total of 6 treatments). All rotations are limited to 10 inches of irrigation water annually. All crops are grown no-till, while other cultural practices (hybrid selection, fertility practices, weed control, etc.) are selected to optimize production. All phases of each rotation are present each year and replicated four times. Irrigations are scheduled to supply water at the most critical stress periods for the specific crops and limited to 1.5 inches/week. Soil water is measured at planting, during the growing season, and at harvest in 1-ft increments to a depth of 8 ft. Grain yields are determined by machine harvest. Nitrogen fertilizer (UAN) was surface applied (stream) in March to all crops (240 lb N/a for corn, 160 lb N/a for sorghum, and 120 lb N/a for wheat). Corn was planted on April 27, 2017, and harvested on October 12, 2017. Grain sorghum was planted on June 2, 2017, and harvested on October 30, 2017. Wheat was planted on September 24, 2016, and abandoned on June 22, 2017.

Results and Discussion
Wheat yields were zero in 2017 because of a severe infestation of wheat streak mosaic virus (Table 1). Weather conditions for summer crops were good in 2017. Precipitation was above normal for April, May, July, August, and September. Corn yields in 2017 were greatest with corn-wheat (211 bu/a) and least with continuous corn (154 bu/a). Grain sorghum yields were greater following corn than following grain sorghum. Despite the favorable precipitation, grain sorghum yields were less in 2017 than the multiyear average (Table 2).
Available soil water at corn planting and harvest was similar for all rotations in 2017 (Table 3). Fallow efficiency was less following corn than following either wheat or grain sorghum. For wheat, available soil water at planting and harvest was greater than the 4-yr average ( Table 4). The only difference observed with grain sorghum was more fallow accumulation for grain sorghum following grain sorghum than following corn. This was consistent with the average fallow accumulation for the past 4 years. Average crop water use was much greater for corn (~6 inch) in 2017 because of the greater than normal precipitation (>22 inch growing season precipitation) while grain sorghum water use was about 2 inch above the long-term average. There were no differences in crop water use due to rotation for either crop.

Acknowledgment
The project was funded in part by Western Kansas Groundwater Management District No. 1.         Occasional Tillage in a Wheat-Sorghum-Fallow Rotation

Summary
Beginning in 2012, research was conducted in Garden City and Tribune, KS, to determine the effect of a single tillage operation every 3 years on grain yields in a wheat-sorghum-fallow (WSF) rotation. Grain yields of wheat and grain sorghum were not affected by a single tillage operation every 3 years in a WSF rotation. Grain yield varied greatly by year from 2014 to 2017. Wheat yields ranged across years from mid-20s to 80 bu/a at Tribune and about 10 (hail damage) to near 60 bu/a at Garden City. Grain sorghum yields ranged from less than 60 to greater than 140 bu/a, depending upon year and location. In no year or location, were grain yields significantly affected by a single tillage operation. This indicates that if a single tillage operation is needed to control troublesome weeds, that grain yields will not be significantly affected. Furthermore, if weed populations were high enough to cause yield reductions, then tillage might improve yields.

Introduction
Previous research has shown lower dryland wheat and grain sorghum yields with reduced tillage compared with no-tillage in a wheat-sorghum-fallow (WSF) rotation. The reduced tillage systems generally used four or more tillage operations in the 3-yr rotation. With increased incidence of herbicide resistant weeds, the use of a complete no-tillage system may not be economical and tillage may be needed for effective control. The objective of the research project is to determine the effect of a single tillage operation every 3 years on grain yields in a WSF rotation.

Procedures
Research on occasional tillage intensities in a predominantly no-tillage WSF rotation at the Kansas State University Southwest Research-Extension Center research stations at Garden City and Tribune was initiated in 2012. The three tillage treatment intensities in this study are a single tillage in May or June during fallow, a single tillage after wheat harvest, and a complete no-tillage system. A sweep plow was used for all tillage operations. When needed, herbicides were used to control weeds during fallow for all treatments. All treatments used herbicides for in-crop weed control. All other cultural practices (variety/hybrid, seeding rate, fertilization, etc.) were the same for all treatments.

Results and Discussion
Weeds were effectively controlled in all treatments and there were no visual differences in weed population across treatments.
At Tribune, wheat yields were 27 to 30 bu/a in 2017 compared with 75 to 80 bu/a in 2016 (Table 1). Yields were reduced by wheat streak mosaic in 2017. There were no significant yield differences among tillage treatments in any year or across years. Grain sorghum yields were greater in 2017 than in any previous years ranging from 141 to 147 bu/a (Table 2). Similar to wheat, there were no significant yield differences among tillage treatments in any year or averaged across years.
At Garden City, wheat yields in 2017 were 19-23 bu/a (Table 3), and wheat yields were reduced in the fall of 2016 by wheat streak mosaic and dry conditions. Wheat yields in 2014 were severely reduced by hail. There were no significant yield differences among tillage treatments in any year or averaged across years. Grain sorghum yields in 2017 were less than half the yield of 2016 (Table 4), due to dry conditions late in the growing season. Similar to wheat, there were no significant yield differences among tillage treatments in any year or averaged across years.
In other research (Schlegel et al., 2018), reduced tillage systems produced lower yields than a complete no-tillage system in a WSF rotation. However, in this study, a single tillage operation in a 3-yr WSF rotation did not affect wheat or grain sorghum yields from 2014 to 2017 at Garden City or Tribune, KS.

Summary
This study was conducted from 2008 to 2017 at the Kansas State University Southwest Research-Extension Center near Tribune, KS. The purpose of the study was to identify whether more intensive cropping systems can enhance and stabilize production in rainfed cropping systems to optimize economic crop production, more efficiently capture and utilize scarce precipitation, and maintain or enhance soil resources and environmental quality. The crop rotations evaluated were continuous grain sorghum (SS), wheat-fallow (WF), wheat-corn-fallow (WCF), wheat-sorghum-fallow (WSF), wheat-corn-sorghum-fallow (WCSF), and wheat-sorghum-corn-fallow (WSCF). All rotations were grown using no-tillage practices except for WF, which was grown using reduced-tillage. The efficiency of precipitation capture was not greater with more intensive rotations. Length of rotation did not affect wheat yields. Corn and grain sorghum yields were about 50% greater when following wheat than when following corn or grain sorghum. Grain sorghum yields were about 40% greater than corn in similar rotations.

Introduction
The change from conventional tillage to no-tillage cropping systems has allowed for greater intensification of cropping in semi-arid regions. In the central High Plains, wheat-fallow (1 crop in 2 years) has been a popular cropping system for many decades. This system is being replaced by more intensive wheat-summer crop-fallow rotations (2 crops in 3 years). There has also been increased interest in further intensifying the cropping systems by growing 3 crops in 4 years or continuous cropping. This project evaluates several multi-crop rotations that are feasible for the region, along with alternative systems that are more intensive than 2-or 3-year rotations. The objectives are to 1) enhance and stabilize production of rainfed cropping systems using multiple crops and rotations, using best management practices to optimize capture and utilization of precipitation for economic crop production, and 2) enhance adoption of alternative rainfed cropping systems that provide optimal profitability.

Experimental Procedures
The All rotations are grown using no-tillage (NT) practices except for WF, which is grown using reduced-tillage (RT). All phases of each rotation are present each year. Plot size is a minimum of 100 × 450 ft. In most instances, grain yields were determined by harvesting the center 60 ft (by entire length) of each plot with a commercial combine and determining grain weight with a weigh-wagon or combine yield monitor. Soil water was measured in 12-inch increments to 96 inches near planting and after harvest either gravimetrically (RT WF) or by neutron attenuation (NT plots).

Results and Discussion
Precipitation averaged 101% of normal (17.90 in.) across the 10-yr study period and was near normal (+/-15%) in 6 out of 10 years with three wet years (>20% above normal) and one exceptionally dry year (42% of normal) (Figure 1). Fallow accumulation, fallow efficiency, and profile available water at wheat planting was greater with WF than all other wheat rotations (Table 1). The fallow efficiencies of the 3-and 4-yr NT rotations were only 50-68% of WF under RT. With more water available, crop water use was also greater with WF than with wheat in other rotations. There were no differences in available water at wheat planting or crop water use among the 3-and 4-yr rotations.
Fallow accumulation prior to corn planting and profile available soil water at planting was greater following wheat (WCF or WCSF) than following grain sorghum (WSCF) ( Table 1). However, the fallow period following wheat was longer, resulting in low fallow efficiencies (~17%) following wheat and only 25% following sorghum. Similar to wheat, corn water use was greater with greater available soil water at planting. Grain sorghum responded similarly to corn, with greater fallow accumulation and soil water at planting (and greater crop water use) when following wheat than following corn or sorghum. Again, fallow efficiencies prior to grain sorghum were low (16-23%).
Wheat yields were lower than normal in 2017 because of damage from wheat streak mosaic virus (Figure 2). The effect of cropping systems was not consistent across years with WF sometimes in the highest yielding group and sometimes in the lowest yielding group. Averaged across the 10 years, cropping system had little effect on wheat yields.
Grain sorghum yields were very good in 2017 with all treatments producing yields of 135 bu/a or greater (Figure 3). In contrast to previous years, grain sorghum yields following corn or sorghum were not much lower than following wheat. However, average grain sorghum yields following wheat were about 50% greater than following corn or sorghum.
Corn yields were also very good in 2017 ( Figure 4) with all rotations yielding 115 bu/a or more. Corn yields following wheat in either the 3-or 4-yr rotations were always greater than corn yields following grain sorghum, except in 2015 where corn yields following sorghum (wsCf) were greater than wCf. On average, corn yields following wheat were about 50% greater than following grain sorghum.
When examining grain yields across crops, the greatest yields were produced by grain sorghum following wheat (either wSf or wScf) of about 80 bu/a ( Figure 5). These yields were about 40% greater than corn following wheat (wCf or wCsf). Sorghum yields following wheat were about 50% greater than sorghum following corn or sorghum (wcSf or SS) while corn yields following wheat (wCf or wCsf) were also about 50% greater than following sorghum.    Tillage Intensity in a Long-Term Wheat-

Summary
This study was initiated in 1991 at the Kansas State University Southwest Research-Extension Center near Tribune, KS. The purpose of the study was to identify the effects of tillage intensity on precipitation capture, soil water storage, and grain yield in a wheat-sorghum-fallow rotation. Grain yields of wheat and grain sorghum increased with decreased tillage intensity in a wheat-sorghum-fallow (WSF) rotation. In 2017, available soil water at sorghum planting was greater for reduced tillage (RT) than no-tillage (NT) or conventional tillage (CT). For wheat there were no differences in available soil water at planting. Averaged across the 17-yr study, available soil water at wheat planting was similar for RT and NT and about 1 inch greater than CT. For sorghum, average available soil water at planting was greater in the order RT>NT>CT. Averaged across the past 17 years, NT wheat yields were 4 bu/a greater than RT and 6 bu/a greater than CT. Grain sorghum yields in 2017 were similar for long-term NT and short-term NT while greater than CT. Averaged across the past 17 years, sorghum yields with long-term NT have been 57% greater than with short-term NT (74 vs. 47 bu/a).

Experimental Procedures
Research on different tillage intensities in a WSF rotation at the Tribune, KS, unit of the Southwest Research-Extension Center was initiated in 1991. The three tillage intensities in this study are conventional (CT), reduced (RT), and no-tillage (NT). The CT system was tilled as needed to control weed growth during the fallow period. On average, this resulted in 4 to 5 tillage operations per year, usually with a blade plow or field cultivator. The RT system originally used a combination of herbicides (1 to 2 spray operations) and tillage (2 to 3 tillage operations) to control weed growth during the fallow period; however, in 2001, the RT system was changed to using NT from wheat harvest through sorghum planting (short-term NT) and CT from sorghum harvest through wheat planting. The NT system exclusively used herbicides to control weed growth during the fallow period. All tillage systems used herbicides for in-crop weed control.

Soil Water
The amount of available water in the soil profile (0 to 8 ft) at wheat planting varied greatly from year to year (Figure 1). In 2017, available soil water at wheat planting was greater with RT than NT and least with CT. Averaged across the 16-yr study, available soil water at wheat planting was similar for RT and NT (about 7 inches) and about 1 inch greater than CT. Similar to wheat, the amount of available water in the soil profile at sorghum planting varied greatly from year to year (Figure 2). In 2017, available soil water at sorghum planting was greater with RT than NT and least with CT. On average, available soil water at sorghum planting was greater with RT than NT and NT was greater than CT.

Grain Yields
Wheat yields in 2017 were low because of severe infestation of wheat streak mosaic (Table 1). Since 2001, wheat yields have been depressed in 11 of 17 years, primarily because of lack of precipitation, while winterkill reduced yields in 2015 and disease in 2017. Reduced tillage and NT increased wheat yields. On average, wheat yields were 6 bu/a higher for NT (23 bu/a) than CT (17 bu/a). Wheat yields for RT were 2 bu/a greater than CT even though both systems had tillage prior to wheat. Yields of NT were significantly less than CT or RT in only 1 of the 17 years.
Grain sorghum yields in 2017 were more than twice as high as the long-term average ( Table 2). Sorghum yields were similar for NT and RT with both being greater than CT. The yield benefit from reducing tillage is greater for grain sorghum than wheat. Grain sorghum yields for RT averaged 17 bu/a more than CT, whereas NT averaged 27 bu/a more than RT. For sorghum, both RT and NT used herbicides for weed control during fallow, so the difference in yield could be attributed to short-term compared with long-term NT. This yield benefit with long-term vs. short-term NT has been observed in most years since the RT system was changed in 2001. Averaged across the past 17 years, sorghum yields with long-term NT have been 57% greater than with short-term NT (74 vs. 47 bu/a).   Tillage

Summary
In 1996, an effort began to quantify soil water storage, crop water use, and crop productivity on dryland systems in western Kansas. Research on 4-year crop rotations with wheat and grain sorghum was initiated at the Southwest Research-Extension Center near Tribune, KS. Rotations were wheat-wheat-sorghum-fallow (WWSF), wheat-sorghum-sorghum-fallow (WSSF), and continuous wheat (WW). Soil water at wheat planting averaged about 9 in. following sorghum, which is about 3 in. more than the average for the second wheat crop in a WWSF rotation. Soil water at sorghum planting was only about 1 in. less for the second sorghum crop compared with sorghum following wheat. Grain yield of recrop wheat averaged about 80% of the yield of wheat following sorghum. Grain yield of continuous wheat averaged about 60% of the yield of wheat grown in a 4-year rotation following sorghum. Generally, wheat yields were similar following one or two sorghum crops. Similarly, average sorghum yields were the same following one or two wheat crops. Yield of the second sorghum crop in a WSSF rotation averages ~65% of the yield of the first sorghum crop.

Introduction
In recent years, cropping intensity has increased in dryland systems in western Kansas. The traditional wheat-fallow system is being replaced by wheat-summer crop-fallow rotations. Research was conducted to better understand if more intensive cropping is feasible with concurrent increases in no-tillage. Objectives of this research were to quantify soil water storage, crop water use, and crop productivity of 4-year and continuous cropping systems.

Experimental Procedures
Research on 4-year crop rotations with wheat and grain sorghum was initiated in 1996 at the Tribune unit of the Southwest Research-Extension Center. Rotations were WWSF, WSSF, and WW. No-tillage was used for all rotations except for the first two years where reduced tillage was used for wheat following sorghum. Available water was measured in the soil profile (0 to 6 ft) at planting and harvest of each crop. The center of each plot was machine harvested after physiological maturity, and yields were adjusted to 12.5% moisture.

Soil Water
The amount of available water in the soil profile (0 to 6 ft) at wheat planting varied greatly from year to year (Figure 1). In 2017, available soil water was greater for wheat following sorghum and for wheat following wheat compared to the long-term average. Soil water was similar following fallow after either one or two sorghum crops and averaged about 9 in. across the 21-year study period. Water at planting of the second wheat crop in a WWSF rotation was generally less than at planting of the first wheat crop, except in 1997 and 2003. Soil water for the second wheat crop averaged more than 3 in. (or about 40%) less than that for the first wheat crop in the rotation. Continuous wheat averaged about 0.8 in. less water at planting than the second wheat crop in a WWSF rotation.
Similar to wheat, the amount of available water in the soil profile at sorghum planting varied greatly from year to year ( Figure 2) and available water at sorghum planting was greater than the long-term average. Soil water was similar following fallow after either one or two wheat crops and averaged about 8 in. over 22 years. Water at planting of the second sorghum crop in a WSSF rotation was generally less than that at planting of the first sorghum crop. Averaged across the entire study period, the first sorghum crop had about 1.3 in. more available water at planting than the second crop.

Grain Yields
In 2017, wheat yields were severely decreased by an infestation of wheat streak mosaic virus (Table 1). Averaged across 21 years, recrop wheat (the second wheat crop in a WWSF rotation) yielded about 80% of first-year wheat crop in WWSF. Before 2003, recrop wheat yielded about 70% of first-year wheat. Wheat yields following two sorghum crops are 2 bu/a greater than following one sorghum crop. In most years, continuous wheat yields have been similar to recrop wheat yields, but in several years (2003, 2007, 2009, and 2014), recrop wheat yields were considerably greater than continuous wheat yields.

A. Schlegel and D. Bond
Summary Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated grain sorghum in western Kansas. In 2017, N applied alone increased yields 53 bu/a, whereas N and P applied together increased yields up to 67 bu/a. Averaged across the past 10 years, N and P fertilization increased sorghum yields up to 77 bu/a. Application of 80 lb/a of N (with P) was sufficient to produce almost 90% of maximum yield in 2017, which is slightly less than the 10-yr average. Application of potassium (K) has had no effect on sorghum yield throughout the study period. Average grain N content reached a maximum of ~0.7 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P 2 O 5 /bu) and grain K content reached a maximum of 0.19 lb/bu (0.23 lb K 2 O/bu). At the highest N, P, and K rate, apparent fertilizer recovery in the grain was 32% for N, 66% for P, and 39% for K.

Introduction
This study was initiated in 1961 to determine responses of continuous grain sorghum grown under flood irrigation to N, P, and K fertilization. The study is conducted on a Ulysses silt loam soil with an inherently high K content. The irrigation system was changed from flood to sprinkler in 2001.

Procedures
This field study is conducted at the Tribune, KS, unit of the Kansas State University Southwest Research-Extension Center. Fertilizer treatments initiated in 1961 are N rates of 0, 40, 80, 120, 160, and 200 lb/a of N without P and K; with 40 lb/a of P 2 O 5 and zero K; and with 40 lb/a of P 2 O 5 and 40 lb/a of K 2 O. All fertilizers are broadcast by hand in the spring and incorporated before planting. The soil is a Ulysses silt loam. Sorghum (Pioneer 85G46 in 2008-2011, Pioneer 84G62 in 2012-2014, Pioneer 86G32 in 2015, and Pioneer 84G62 in 2016 was planted in late May or early June. Irrigation is used to minimize water stress. Sprinkler irrigation has been used since 2001. The center two rows of each plot are machine harvested after physiological maturity. Grain yields are adjusted to 12.5% moisture. Grain samples were collected at harvest, dried, ground and analyzed for N, P, and K concentrations. Grain N, P, and K content (lb/bu) and removal (lb/a) were calculated. Apparent fertilizer N recovery in the grain (AFNR g ) was calculated as N uptake in treatments receiving N fertilizer minus N uptake in the unfertilized control divided by N rate. The same approach was used to calculate apparent fertilizer P recovery in the grain (AFPR g ) and apparent fertilizer K recovery (AFKR g ). Aerial application for grasshoppers was applied on July 18 and hail damage occurred on August 18.

Results
Grain sorghum yields in 2017 were 8% lower than the 10-year average (Table 1). Nitrogen alone increased yields 53 bu/a while P alone increased yields less than 10 bu/a. However, N and P applied together increased yields up to 67 bu/a. Averaged across the past 10 years, N and P applied together increased yields up to 77 bu/a. In 2017, 40 lb/a of N (with P) produced about 88% of the maximum yield, which is greater than the 10-year average of 83%. The 10-year average for 80 lb/a of N (with P) and 120 lb/a of N (with P) was 93 and 95% of the maximum yield, respectively. Sorghum yields were not affected by K fertilization, which has been the case throughout the study period.

Seeding Rate for Dryland Wheat Introduction
The purpose of this project is to determine appropriate seeding rates for dryland winter wheat in western Kansas. In recent years, there appears to be an increase in seeding rate without corresponding increase in grain yields. A preliminary study conducted in 2014 found no yield benefit from increasing seeding rates from 30 to 75 lb seed/a for 4 wheat varieties at Tribune, while a similar study at Garden City suffered severe hail damage causing yields to be less than 10 bu/a. The objective is to evaluate seeding rates on grain yield of several popular wheat varieties representing a range of genetic backgrounds and tillering ability under dryland conditions at three sites in western Kansas.

Experimental Procedures
was fertilized pre-plant with 90 lb N/a at Colby, and topdressed with 100 lb N/a at Garden City, and 80 lb N/a at Tribune. In 2017, wheat was fertilized pre-plant with 60 lb N/a at Colby, and topdressed with 80 lb N/a at Garden City, and 80 lb N/a at Tribune. Herbicides were applied in the spring for weed control: Ally Extra (

Results and Discussion
Growing season precipitation was below normal for Garden City all years, but normal to above normal for Tribune and Colby. In addition, precipitation was infrequent and variable across the growing seasons. In 2015, precipitation was high in May (6.38 in. in Garden City, 6.16 in. at Tribune, and 6.42 in. at Colby) making up for a dry winter and early spring. For 2016, rainfall was above normal for Tribune, slightly below normal for Garden City, and below normal at Colby. April was wet with 5.16 in. at Tribune,4.59 in. at Garden City,and 5.64 in. at Colby. In 2017, precipitation was above average at Tribune for April (4.67 in.) and May (5.00 in.), however, wheat streak mosaic virus reduced grain yield. At Garden City conditions were very dry in the fall of 2016 (0.3 in. between October and January), and the majority of the precipitation (6.58 in.) occurred in March and April. At Colby, conditions were extremely dry at seeding time followed by above normal precipitation in the late spring. A blizzard event on April 30 to May 1, 2017 resulted in the wheat being completely laid flat at the boot stage at Tribune and Colby with 14-20 inches of snow on top.
In 2015, averaged across seeding rates at Tribune, T158 and Winterhawk produced the greatest yields with TAM 111 producing the lowest yields ( At all sites averaged across varieties in 2015, there was a positive yield response to increased seeding rates with greatest response when increasing from 30-60 lb/a with minimal response above 60 lb/a. Wheat yields were very good at all locations in 2016 ( Table 2). The response to variety and seeding rate varied greatly across locations. Averaged across seeding rates, Byrd produced the greatest yields at Tribune while it produced the lowest yields at Garden City. Winterhawk and T158 were the lowest yielding at Tribune while they were the highest yielding at Garden City and Colby. There was a significant positive yield response to increased seeding rate at Tribune and Colby but no significant response to seeding rate at Garden City.
Wheat yields were increased by increased seeding rates at all locations in 2017 (Table 3). Wheat yields were the lowest at Tribune (significant wheat streak mosaic virus damage) and greatest at Colby. TAM 114 was in the highest yielding group at all locations. The ranking of the other varieties depended upon location. The dry fall conditions in 2016 at Garden City likely reduced tiller development, resulting in reduced wheat yields at seeding rates less than 60 lb/a. Relative differences in growth stage among varieties at the time of the late spring blizzard may have affected their yield potential, however this was very difficult to assess.
Averaged across years (2015-2017), T158 was the highest yielding variety at Garden City and Colby (Table 4). Byrd was the highest yielding variety at Tribune, but the lowest yielding at the other two locations. At all locations, grain yields were increased by increased seeding rate. When averaged across all locations and years, yields were increased 8 bu/a by increasing seeding rate from 30 to 60 lb/a and an additional 3 bu/a when seeding rate was increased to 90 lb/a. There was not a significant variety × seeding rate interaction as all varieties responded positively to increased seeding rate. These results support a previous Kansas State University recommendation that the economic optimum seeding rate for rainfed winter wheat production in western Kansas is 60 lb/a, while the highest yield can be obtained with a 75 lb/a seeding rate.
In 11 site-years of this study, the variety × seeding rate interaction has only been significant in 2 of 11 years. At those two site years (Garden City and Tribune, 2015), increasing seeding rates resulted in increased yield for stripe rust-susceptible varieties. We hypothesize that higher seeding rates in the stripe rust-susceptible varieties partially compensated for lower per plant grain yield due to stripe-rust reducing productive leaf area. In general, the data collected in this study would not support the need for variety-specific seeding rate recommendations.

Wheat Stubble Height on Subsequent Corn Introduction
Seeding of summer row crops throughout the west-central Great Plains often occurs following wheat in a 3-year rotation (wheat-summer crop-fallow). Wheat residue provides numerous benefits, including evaporation suppression, delayed weed growth, improved capture of winter snowfall, and soil erosion reductions. Stubble height affects wind velocity profile, surface radiation interception, and surface temperatures, all of which affect evaporation suppression and winter snow catch. Taller wheat stubble is also beneficial to pheasants in postharvest and overwinter fallow periods. Using stripper headers increases harvest capacity and provides taller wheat stubble than previously attainable with conventional small-grains platforms. Increasing wheat cutting heights or using a stripper header should further improve the effectiveness of standing wheat stubble. The purpose of this study is to evaluate the effect of wheat stubble height on subsequent summer row crop yields.

Experimental Procedures
This study was conducted at the Southwest Research-Extension Center dryland station near Tribune, KS. From 2007 through 2017, corn and grain sorghum were planted into standing wheat stubble of three heights. Optimal (high) cutter-bar height is the height necessary to maximize both grain harvested and standing stubble remaining (typically around two-thirds of total plant height), the short cut treatment was half of optimal cutter-bar height, and the third treatment was stubble remaining after stripper header harvest. For 2017, these heights were 20, 10, and 30 in. (cut after 2016 wheat harvest). In 2017, corn and grain sorghum were seeded at rates of 15,000 seeds/a and 45,000 seeds/a, respectively. Nitrogen was applied to all plots at a rate of 80 lb/a. Starter fertilizer (10-34-0 nitrogen-phosphorus-potassium (N-P-K)) was surface-dribbled off-row at a rate of 7 gal/a. Plots were 40 × 60 ft, with treatments arranged in a randomized complete block design with six replications. Two rows from the center of each plot were harvested with a plot combine for yield and yield component analysis. Soil water mea-surements were obtained with neutron attenuation to a depth of 6 ft in 1-ft increments at seeding and harvest to determine water use and water use efficiency.

Results and Discussion
The 2017 growing season was above normal for precipitation with more than 4 inches received in April, May, and July. This produced above average yields for both corn and sorghum (Tables 1-4). With the good growing conditions, stubble height had little effect on corn yield or other parameters. When averaged across 2007 to 2017, corn yields were 9 bu/a greater in high or strip-cut than low-cut wheat stubble (Table 2). Biomass production and water use efficiency were also greater with the taller stubble.
Grain sorghum yields in 2017 were not affected by stubble height (Table 3). When averaged across years from 2007 through 2017, the highest yields were obtained in the high-cut stubble but were not significantly greater than the other stubble heights ( Table  4). None of the other measured parameters for grain sorghum were affected by wheat stubble height except for greater water use efficiency in high-cut vs. low-cut stubble.

Summary
This study compared drilled planted sorghum at four seeding rates to planted sorghum at three different nitrogen (N) fertility levels at two locations in southwest Kansas (Garden City and Tribune). In 2017, at the Garden City location using a John Deere experimental sorghum drill and at Tribune using a regular John Deere drill, higher yields were produced with drilled seeded sorghum with 60,000 and 80,000 seeds/a at both locations. Likewise, at both locations, there was no difference in yield between the planted and drilled sorghum at the same seeding rate. Nitrogen fertilizer did not interact with seeding rate to affect yield in Garden City, but significantly increased yield with an increased rate of application at the Tribune location. In general, the effect of nitrogen rates and seeding rates on sorghum yield was observed to be influenced by other management and environmental factors. The results of this study suggested that there was no yield penalty for drilling or planting sorghum at the same seeding rate.

Introduction
Drilled sorghum is normally done at the super-high population at row spacing between 7.5 and 10 inches, compared to rows planted at the spacing between 15 and 30 inches. Thompson (1983) growing super-thick sorghum at the Hays Research Station from 1974-1977, found that sorghum planted in narrow rows (12-18 in.) often produced higher yields than when planted in wide rows (24-40 in.). Norwood (1982) in Garden City repeated Thompson's work also concluded that yield of high population narrow row sorghum could exceed that of the low population-wide row when subsoil moisture and precipitation were adequate. The conclusion from the work of Thompson and Norwood was that subsoil moisture and precipitation were big drivers for the high population, narrow row sorghum to equal or exceed the yield of the low population wide row. Since then, most researchers have found yield response to plant population to be variable depending on the environment. Overall, the consensus is that under conditions of adequate moisture, the yield of high population sorghum can continue to increase but can decrease under dry conditions. Moisture still remains the key for successful dryland sorghum production in southwest Kansas. Thus, the very familiar saying, "moisture and fertility are joined at the hip." Thompson's and Norwood's work did not evaluate narrow row at population under 25,000 seeds/a and at a spacing less than 10 in. We hypothesized that drilled sorghum at lower population could make better use of water resources and produce similar yields to drilled sorghum at higher populations, and planted sorghum at the same population. Thus, the objective of this study is to evaluate drilled sorghum at different populations ranging from 20,000 to 80,000 seeds/a at a row spacing of 10 in. or less at different nitrogen rates. Furthermore, most farmers in southwest Kansas own both a drill and a planter. Thus, it is not just an agronomic issue, but it is also about getting better value from a single piece of equipment in an already economically challenging wheat-sorghum-fallow production system.

Procedures
Experiments were conducted under dryland conditions at two locations in western Kansas (Southwest Research-Extension Center in Garden City and Tribune) to determine the interaction of seeding rate and nitrogen rate under narrow row sorghum in southwest Kansas. At the Garden City location, a John Deere sorghum experimental drill was used, while at the Tribune location research plot-sized equipment was used.
The experimental design was a split plot design with seeding rate as the main plot and nitrogen rate as the subplot. The main plot size in Garden City was 30-ft wide × 40-ft long and the subplots were 10-ft wide × 40-ft long. In Tribune, the main plot was 60-ft wide × 50-ft long and the subplots were 20-ft wide × 50-ft long.

Planting Dates and Plot Layout
Sorghum variety Dekalb 3707 was planted at both locations, on June 12, 2017, in Garden City and June 6, 2017, in Tribune. A randomized complete block design with a 5 × 3 factorial treatment arrangement with four replications was used at both locations. At Garden City, sorghum was planted on 15 in. row spacing using a 40-ft wide John Deere experimental sorghum no-till drill. The drilled seeding rates were 20,000, 40,000, 60,000, and 80,000 seeds/a and the planted sorghum was seeded at 20,000 seeds/a with a planter at 30 in. row spacing with a John Deere 7300 planter.
At Tribune, sorghum was planted on 7.5 in. row spacing with a John Deere 1590 no-till drill. The drilled seeding rates were 20,000, 40,000, 60,000, and 80,000 seeds/a and the planted sorghum was seeded at 40,000 seeds/a with a planter at 30 in. row spacing with a John Deere 1700 planter. The three factors were three nitrogen rates (0, 50, and 100 lb/a) at both locations.
At both locations, potassium (K) and phosphorus (P) were applied based on the soil test recommendations provided by the Kansas State University Department of Agronomy Soil and Plant Testing Laboratory, Manhattan, KS.
Herbicide management at Garden City was the application of glyphosate at 1.25 qt/a + Harness at 2.5 pt/a + Starane Ultra at 0.75pt/a applied pre-plant on June 1, 2017. At Tribune, Atrazine at 1 lb/a + Rifle at 16 oz /a was applied early on February 16, 2017, followed by 80 oz/a Lumax E2 + 48 oz/a Gramoxone + 0.50% v/v NIS and applied pre-emergence on June 10, 2017.

Data Collection and Analysis
The Garden City location was harvested using a 7.5-ft wide head plot combine and Tribune was were harvested with a 5-ft wide head. Crop weights were adjusted to 13% moisture.
Data were analyzed using PROC GLM with SAS 9.4 (SAS Institute, Inc., Cary, NC) and a model statement appropriate for a factorial design. Treatment means were separated by Fisher's projected least significant difference test.

Garden City
Drilled sorghum at the higher populations produced the highest yield, but there was no difference in grain yield between the planted sorghum at 20,000 seeds/a and the drilled sorghum at the same seeding rate (Figure 1). Nitrogen rate did not interact with population or affect sorghum yield independently in the study.

Tribune
Similar to Garden City, higher yield was produced at the higher drilled seeding rate and there was no difference in grain yield between planted sorghum and drilled sorghum at the same seeding rate (Figure 2). Sorghum yield increased with the increased rate of nitrogen fertilizer (Figure 3).

Conclusion
The result observed in the study can be attributed to the influence of planting equipment, planting date, and environmental condition. At the Garden City location, the later planting date and the drier condition at and after planting might have attributed to the low yield obtained. At the Tribune location, the response to nitrogen fertilizer may be attributed to the influence of a hail storm on August 18. These results indicate the complexity of seeding rate with the management and environmental condition. Additionally, these results suggest that there is no yield penalty for drilling or planting sorghum at the same population.

Introduction
Forage variety testing has shown yield and nutritive value differences across forage sorghum and sorghum × sudan varieties (Holman et al. 2016(Holman et al. , 2018. Growers commonly report differences in palatability of free-choice sorghum hay fed to cattle (Holman, unpublished data). The differences in palatability may be in part related to maturity of the forage and forage type. Therefore, one cultivar of each sorghum type was harvested at different maturities for yield and nutritive value to gain better insight into feed value differences.

Study Objectives
1. Compare yield and nutritive value differences of forage sorghum and sorghum × sudan BMR and non-BMR types. 2. Evaluate maturity differences (boot, heading, flowering, and soft dough) on forage yield and nutritive value.

Experimental Procedures
Annual forages were grown in 2017 at the Southwest Research-Extension Center near Garden City, KS. The study design was a randomized complete block design with four replications. Treatment was forage sorghum type (forage sorghum and sorghum × sudan) with and without the BMR trait, harvested at boot, heading, flowering, and soft dough for a total of 16 treatments. Plots were 15-ft wide × 60-ft long. Forage sorghum cultivars were non-BMR 'Canex' forage sorghum (FS), BMR 'Canex 210' forage sorghum (FSBMR), non-BMR 'Super Sugar' sorghum × sudan (SS), and BMR Sweet Six sorghum × sudan (SSBMR). Sorghum cultivars were planted on June 1, 2017, and harvested at boot, heading, flowering, and soft dough growth stages.

Results and Discussion
There was a significant interaction between forage type and growth stage for ADF and NDF (Table 1). Acid detergent fiber ranged from 34.4% (FS at boot) to 39.9% (SSBMR at heading), and NDF ranged from 50.4% (FS at dough) to 58.7% (SSBMR at flowering). Highly digestible forage grass would have an ADF < 35% and NDF < 50%. All of the fiber contents measured in this study would be considered lower-quality and less digestible regardless of forage type or maturity. The significant interaction was caused by SSBMR having greater ADF and NDF concentration at heading and dough than other forage types, and SSBMR having lesser ADF and NDF at boot. This suggests fiber content of SSBMR rapidly increased post-heading, resulting in forage with lower digestibility post-heading. It may be more critical to harvest SSBMR early than other forage types for best forage quality. Growth stage affected yield, ash, lignin, TDN, CP, milk/ton, and milk/a ( Table 2). All forage attributes were affected by forage type (Table 3).

Growth Stage
Dry matter yield was greatest at dough and not different among other growth stages (Table 2). Harvesting at dough stage increases both forage and grain, thus increasing overall yield. These results also suggest a minimal yield penalty by harvesting early, yet harvesting early might increase overall forage quality and palatability. Ash content was highest at boot and lowest at dough. It is unclear why ash tended to be higher with earlier maturity, but might be due to less nutrient uptake as the plants mature. Lignin content was highest at dough and similar across the other growth stages. ADF was higher at boot than dough, while NDF was similar across growth stages. The grain (starch) component of the plant is more digestible and thus likely resulted in lower ADF at dough.
Neutral detergent fiber digestible (NDFD) and in vitro true dry matter digestibility (ITVD) were similar across growth stages. Crude protein decreased with maturity and was highest at boot. RFQ was similar across growth stages. TDN and milk/ton were highest at dough and lowest at boot, correlating with ADF content. The increased digestibility and improved energy at dough was likely due to the grain component of the forage. Milk/ton and milk/a were highest at dough and similar across the other growth stages.

Forage Type
Of the varieties evaluated, dry matter yield of forage sorghum (FSBMR and FS) tended to be greater than sorghum × sudan (SSBMR and SS) in a one-cut hay system (Table 3). Yield can vary greatly among varieties and environment (Holman et al. 2017a(Holman et al. , 2017b(Holman et al. , and 2018). Sorghum × sudan as a group tends to have greater regrowth than forage sorghum, and regrowth was not measured in this study. Ash content was highest in SSBMR and no different than the other forage types. It is unclear why ash content was higher in SSBMR.
Lignin content was highest in SS and FS, and lower in SSBMR and FSBMR, which coincides with the BMR trait having less lignin. Fiber content (ADF and NDF) tended to be higher in sorghum × sudan (SSBMR and SS), than forage sorghum (FSBMR and FS), but the differences between forage types was negligible. Fiber digestibility (NDFD and IVTD) tended to be greater among forage sorghum (FSBMR and FS) than sorghum × sudan (SSBMR and SS), although no difference was observed between FS and SSBMR. This indicates better fiber digestibility of SSBMR compared to SS. Crude protein content was greatest in SSBMR, and FSBMR was greater than FS, indicating BMR improved crude protein content.
Relative feed quality (RFQ) combines fiber digestibility and crude protein to provide a nutrient value index to compare similar forages, total digestible nutrients (TDN) is a measurement of digestibility energy, and milk per ton is a measurement of starch and fiber digestibility. FSBMR and FS had greater RFQ, TDN, and milk per ton than SSBMR or SS, largely caused by the differences in fiber content and fiber digestibility between the two forage types. Milk per acre combines the value of forage quality (milk per ton) and yield (dry matter yield/a) into one term. Milk per acre was greatest with FSBMR and lowest with FS and SSBMR, largely driven by yield/a since forage quality differences were minor among forage types.

Conclusion
Harvesting forage sorghum or sorghum × sudan at early maturity (boot) increased crude protein content, did not reduce yield compared to harvesting at heading or flowering, and would likely improve palatability when fed as free choice hay. However, if feeding as part of a total mixed ration where bunk sorting would be limited, harvesting forage sorghum later at soft dough increased fiber digestibility and yield. SSBMR in this study increased fiber concentration more with plant maturity than the other forage types.
In a one-cut system, forage sorghum will generally provide greater yield than sorghum × sudan, but sorghum × sudan typically has greater regrowth than forage sorghum. BMR forage types had less lignin and greater CP. Fiber content (ADF and NDF) was lower and forage digestibility (NDFD and IVTD) was greater among forage sorghum plots than sorghum × sudan. If regrowth is not required, then BMR forage sorghum can provide the most digestible forage.

A. Schlegel and D. Bond
Summary Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated corn in western Kansas. In 2017, N applied alone increased yields by 70 bu/a, whereas P applied alone increased yields by less than 10 bu/a. Nitrogen and P applied together increased yields up to 130 bu/a. This is 10 bu/a less than the 10-year average, where N and P fertilization increased corn yields up to 140 bu/a. Application of 120 lb/a N (with highest P rate) produced 93% of maximum yield in 2017, which is similar to the 10-year average. Application of 80 instead of 40 lb P 2 O 5 /a increased average yields 10 bu/a. Average grain N content reached a maximum of 0.6 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P 2 O 5 /bu). At the highest N and P rate, apparent fertilizer nitrogen recovery in the grain (AFNR g ) was 42% and apparent fertilizer phosphorus recovery in the grain (AFPR g ) was 61%.

Introduction
This study was initiated in 1961 to determine responses of continuous corn and grain sorghum grown under flood irrigation to N, P, and potassium (K) fertilization. The study is conducted on a Ulysses silt loam soil with an inherently high K content. No yield benefit to corn from K fertilization was observed in 30 years, and soil K levels remained high, so the K treatment was discontinued in 1992 and replaced with a higher P rate.

Procedures
This field study is conducted at the Tribune unit of the Kansas State University Southwest Research-Extension Center. Fertilizer treatments initiated in 1961 are N rates of 0, 40, 80, 120, 160, and 200 lb/a without P and K; with 40 lb/a P 2 O 5 and zero K; and with 40 lb/a P 2 O 5 and 40 lb/a K 2 O. The treatments were changed in 1992; the K variable was replaced by a higher rate of P (80 lb/a P 2 O 5 ). All fertilizers were broadcast by hand in the spring and incorporated before planting. The soil is a Ulysses silt loam. The corn hybrids [Pioneer 34B99 (2008) The corn is irrigated to minimize water stress. Sprinkler irrigation has been used since 2001. The center two rows of each plot are machine harvested after physiological maturity. Grain yields are adjusted to 15.5% moisture. Grain samples were collected at harvest, dried, ground and analyzed for N and P concentrations. Grain N and P content (lb/bu) and removal (lb/a) were calculated. Apparent fertilizer N recovery in the grain (AFNR g ) was calculated as N uptake in treatments receiving N fertilizer minus N uptake in the unfertilized control divided by N rate. The same approach was used to calculate apparent fertilizer P recovery in the grain (AFPR g ). Aerial application for grasshoppers was applied on July 18 and hail damage occurred on August 18.

Results
Corn yields in 2017 were 25% lower than the 10-year average (Table 1). Nitrogen alone increased yields 70 bu/a, whereas P alone increased yields less than 10 bu/a. However, N and P applied together increased corn yields up to 130 bu/a. Maximum yield was obtained with 200 lb/a N with 80 lb/a P 2 O 5. Corn yields in 2017 (averaged across all N rates) were 10 bu/a greater with 80 than with 40 lb/a P 2 O 5 .
The 10-year average grain N concentration (%) increased with N rates but tended to decrease when P was also applied, presumably because of higher grain yields diluting N content (Table 2). Grain N content reached a maximum of 0.6 lb/bu. Maximum N removal (lb/a) was greatest at the highest yield levels, which were attained with 200 lb N and 80 lb P 2 O 5 /a. At the highest N and P rate, AFNR g was 42% and AFPR g was 61%. Similar to N, average P concentration increased with increased P rates but decreased with higher N rates. Grain P content (lb/bu) of about 0.15 lb P/bu (0.34 lb P 2 O 5 /bu) was greater at the highest P rate with low N rates. Grain P removal averaged 29 lb P/a at the highest yields.        *AFNR g and AFPR g = Apparent fertilizer N recovery (grain) and Apparent fertilizer P recovery (grain).

Introduction
Zest (nicosulfuron) and Resolve (rimsulfuron) are herbicides that have long been used in corn to control weedy sorghum species as well as other grasses. Using selections from weedy sorghum species that had developed resistance to the ALS mode of action, commercial sorghum hybrids have been developed. Although these compounds provide excellent control of weedy sorghum species they can be weak on many broadleaf weeds and some grassy species beyond a certain size. Harmony (thifensulfuron), another ALS herbicide long used for weed control in wheat, was also included. Therefore, it was the objective of this study to compare tank mixes of herbicides to augment the weed spectrum of Zest and Resolve.

Experimental Procedures
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, to evaluate weed control and crop response with acetolactase-synthase (ALS) inhibiting herbicides Zest, Resolve, and Harmony in irrigated ALS-resistant grain sorghum. Atrazine and Cinch (S-metolachlor) were also included to augment weaknesses in these compounds. Herbicides were applied preemergence (PRE), early postemergence (EPOST), or PRE followed by postemergence (POST). The experimental area was overseeded with crabgrass and Rox Orange forage sorghum (to simulate shattercane) to supplement naturally occurring weed pressure prior to planting sorghum. Application, environmental, and weed information is shown in Table 1. A tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi was used to apply all herbicides. Plot size was 10 × 35 feet, arranged in a randomized complete block design with four replicates. Soil was a Beeler silt loam with 2.4% organic matter and pH of 7.6. Visual weed control was determined on July 17 and August 30, 2017, which was 6 and 50 days after the POST treatment (DAPT), respectively. Grain yields were determined on November 1, 2017, by mechanically harvesting the center two rows of each plot and adjusting weights to 14% moisture.

Results and Discussion
Palmer amaranth control at 50 DAPT was best when Cinch was applied PRE followed by Zest plus atrazine POST or when Cinch ATZ was applied EPOST with Zest and atrazine (Table 2). Most herbicides provided 95 to 100% crabgrass control at 6 DAPT, and control was complete regardless of herbicide by 50 DAPT. Shattercane control at 50 DAPT was 95% or more with all herbicides except Cinch ATZ applied PRE (50%). Minor sorghum stunting and chlorosis (11 to 15%) was observed when Cinch ATZ was applied EPOST with Zest and atrazine at three days after application, but sorghum had completely recovered within seven days (data not shown). No other visible sorghum injury was observed. Herbicide-treated grain sorghum yielded 48 to 93 bu/a more grain than untreated sorghum. Sorghum yields were best (96 to 105 bu/a) when Cinch or Cinch ATZ was applied PRE followed by Zest and atrazine POST, or when Cinch ATZ was applied with Zest and atrazine EPOST.

Introduction
With the advent of dicamba-tolerant soybean it has been postulated that they will be weeds in the subsequent corn crop. Dicamba has long been used as a foundation for postemergence broadleaf weed control in corn. If dicamba is not effective on dicamba-tolerant volunteer soybean, new tank mixes will be needed. Therefore, it was the objective of this study to test various other compounds to control dicamba-tolerant soybean and broadleaf weeds in corn.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated preemergence (PRE) Armezon, Armezon Pro, and atrazine or these compounds applied postemergence (POST) with glyphosate for control of dicamba-tolerant soybean in field corn. Application, environmental, and weed information is given in Table 1. The experimental area was overseeded with dicamba-tolerant soybean seed prior to planting corn, whereas the Palmer amaranth and green foxtail populations were naturally occurring. Herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi. Plot size was 10 × 35 feet arranged in a randomized complete block design with four replications. Soil for the experiment was a Beeler silt loam with 2.4% organic matter and pH 7.6. Visual weed control ratings were determined on June 20 and September 5, 2017, which was 5 and 82 days after the POST treatments (DAPT), respectively. Grain yields were determined by mechanically harvesting the center two rows of each plot on October 20, 2017, and adjusting weights to 15.5% moisture.

Results and Discussion
Dicamba-tolerant soybean control at 5 DAPT was best when Armezon or Armezon Pro was applied POST with atrazine and glyphosate, or when with Status, atrazine, and glyphosate were applied POST (Table 2). These treatments, along with PRE treatments of Armezon Pro and atrazine, completely controlled soybean at 82 DAPT. Similarly, control of Palmer amaranth and green foxtail was generally best with Armezon Pro and atrazine applied PRE or any herbicide combination applied POST regardless of evaluation date. Corn receiving PRE treatment of any herbicide yielded 41 to 120 bu/a more than the weedy checks; however, corn treated POST with any herbicide treatment yielded 117 to 145 bu/a more grain than the untreated controls.

Introduction
Mesotrione has recently come off of patent and this has greatly reduced its price. This has allowed companies that previously did not have patent rights to include it to broaden the weed spectrum of their tank mixes. Many of these tank mixes, as well as other competitive chemistries have potent preemergence as well as postemergence activity so they may be applied prior to planting then reapplied after corn and escaped weeds have emerged. Therefore, it was the objective of this study to apply a broad array of these compounds at various timings to measure their relative weed control.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated various herbicide premixes and tank mixtures for efficacy at various application timings. Naturally occurring weed populations were supplemented by overseeding the experimental area with quinoa, domesticated sunflower, and Rox Orange forage sorghum prior to corn planting. These species simulated common lambsquarters, common sunflower, and shattercane. Resicore (acetochlor + clopyralid + mesotrione), atrazine, glyphosate, and 2,4-D ester were applied 28 days early preplant (EPP). Preemergence (PRE) treatments included Anthem Maxx, atrazine, glyphosate, Solstice, Callisto (mesotrione), Balance Flexx (isoxaflutole), Keystone NXT (acetochlor + atrazine), Hornet WDG (flumetsulam + clopyralid), SureStart II, Acuron (S-metolachlor + atrazine +mesotrione + bicyclopyrone), and Resicore. Status (diflufenzopyr + dicamba) as well as many of the PRE herbicides were then reapplied as postemergence (POST) treatments. Application, environmental, crop, and weed information is given in Table 1. Herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi. Plot size was 10 × 35 feet, and the experiment was a randomized complete block with four replications. Soil was a Beeler silt loam with pH 7.6 and 2.4% organic matter. Weed control ratings for all species were visually determined on June 19 and August 16, 2017, which was 10 and 68 days after the POST treatments (DAPT), respectively. Corn yields were determined October 18, 2017, by mechanically harvesting the two center rows of each plot and adjusting grain weights to 15.5% moisture.

Results and Discussion
Overall weed control was good with most herbicides, such that kochia, Russian thistle, and quinoa control was 98% or more regardless of treatment or rating date (data not shown). Sunflower control at 10 DAPT was 95% when Anthem Maxx + Solstice + atrazine and glyphosate were applied EPOST, while green foxtail control was 94% with the same treatment at 68 days after postemergence treatment (DAPT; Table 2). Palmer amaranth and green foxtail control at 68 DAPT was 93 and 91%, respectively, when SureStart II + atrazine and glyphosate were applied PRE followed by glyphosate POST. All herbicide-treated corn yielded 34 to 69 bu/a more grain than the untreated control. Yields among herbicide-treated corn plots were lowest when no EPOST or POST application was included.

Introduction
The active ingredient in Liberty, glufosinate, was first reported to have herbicidal activity in 1981. Although it has very broad spectrum capacity to burn most weed species, it does not translocate well in plants so it only kills very small weeds. Further, it could also cause severe damage to crops. With the advent of Liberty Link soybean and corn with excellent resistance to glufosinate, this compound has had renewed interest for weed control. Further as more weeds have developed resistance to glyphosate, Liberty-when used on small weeds-has been shown to provide a suitable substitute. However, like glyphosate it lacks any preemergence weed control. Unlike glyphosate it also needs some assistance when applied to weeds above certain sizes. Therefore, it was the objective of this study to explore tank mixes of atrazine, Capreno (tembotrione + thiencarbazone), Laudis (tembotrione), and Halex GT (S-metolachlor + glyphosate + mesotrione) to enhance weed control provided with Liberty.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated Liberty rates and tank mix partners for postemergence weed control in corn. The experimental area was overseeded with a mixture of kochia, Palmer amaranth, crabgrass, quinoa, and domesticated sunflower seed prior to corn planting. Quinoa and domesticated sunflower were used as surrogates for common lambsquarters and common sunflower, respectively. All postemergence treatments were preceded by a preemergence application of Balance Flexx at 3.0 oz/a + atrazine at 32 oz/a. Herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi. Application, environmental, crop, and weed details are shown in Table 1. Plot size was 10 × 35 feet and arranged in a randomized complete block with four replicates. Soil for the experiment was a Beeler silt loam with pH 7.6 and 2.4% organic matter. Weed control was visually rated on June 12 and August 16, 2017, which was 7 and 72 DAPT, respectively. Corn yields were determined on October 18, 2017, by mechanically harvesting the center two rows of each plot and adjusting grain weights to 15.5% moisture.

Results and Discussion
Control of quinoa, green foxtail, and kochia was 98% or more regardless of herbicide treatment or evaluation date (data not shown) as was common sunflower control (Table 2). Palmer amaranth and crabgrass control was 95% or more regardless of herbicide treatment at 7 DAPT. Postemergence applications of Liberty at any rate alone controlled Palmer amaranth 85 to 88% at 72 DAPT, whereas tank mixing any herbicide with Liberty increased control 7 to 15%. Crabgrass control was 89 to 96% at 72 DAPT with all treatments except when Liberty at 22 oz/a was applied with Diflexx at 10 oz/a (84%). Corn yields did not differ among herbicide-treated plots, but each herbicide treatment increased yield 118 to 149 bu/a relative to the untreated controls.

Introduction
Mesotrione, a key component of Acuron (S-metolachlor + atrazine + mesotrione + bicyclopyrone), has recently come off patent, allowing it to be used in several novel premixes such as Instigate (rimsulfuron + mesotrione), Realm Q, and Resicore (acetochlor + clopyralid + mesotrione). Corvus has a different mode of action than these compounds and is commercially competitive with them. Many of these premixes can be augmented by adding Cinch ATZ (S-metolachlor + atrazine), glyphosate, atrazine, or dicamba. Therefore, it was the objective of this study to compare the weed control of these herbicides at preemergence and postemergence application timings.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated residual weed control with herbicides applied preemergence (PRE) or early postemergence (EPOST) when corn had one to two true leaves. The experimental area was overseeded with Palmer amaranth, kochia, crabgrass, quinoa, and domesticated sunflower seed prior to corn planting. Quinoa and domesticated sunflower were used as surrogates for common lambsquarters and common sunflower. All herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi. Application, environmental, crop, and weed information is shown in Table 1. Plot size was 10 × 35 feet and arranged in a randomized complete block with four replicates. Soil was a Beeler silt loam with pH 7.6 and 2.4% organic matter. Weed control was visually determined on June 16 and August 17, 2017, which was 11 and 73 days after the early postemergence treatments (DAPT), respectively. Corn yields were determined by mechanical harvest of the two center rows of each plot on October 19, 2017, and adjusting grain weights to 15.5% moisture.

Results and Discussion
Palmer amaranth, kochia, quinoa, common sunflower, and green foxtail control was 97% or more regardless of herbicide or evaluation date, and did not differ between any treatments (data not shown). Crabgrass was controlled 94% or more by all treatments except Realm Q + atrazine, dicamba, and glyphosate at 11 and 73 DAPT; and Corvus + atrazine, dicamba and glyphosate at 73 DAPT (Table 2). The exceptional weed control with these herbicides resulted in grain yields that were 108 to 125 bu/a greater than in the untreated plots. However, no differences occurred among herbicide treatments for corn yield.

Introduction
Diflexx Duo is a very competitive herbicide package mix with Capreno, Halex GT (S-metolachlor + atrazine + mesotrione + glyphosate), Armezon (topramezone), Degree Xtra (acetochlor + atrazine), and Bicep II Magnum (S-metolachlor + atrazine). Each of these package mixes has different levels of preemergence and postemergence weed control. Adding other compounds-such as Liberty (glufosinate), Outlook (dimethenamid-P), and Status (dicamba + diflufenzopyr)-can often improve overall weed control. Therefore, it was the objective of this study to compare these compounds alone and with other products to measure their overall weed control.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated the premix of Diflexx Duo with tank mixtures for postemergence efficacy compared to standards in corn. All herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi when corn was 5 to 8 inches tall. Application, environmental, crop, and weed information is shown in Table 1. Plot size was 10 × 35 feet and arranged in a randomized complete block with four replicates. Soil for the experiment was a Beeler silt loam with pH 7.6 and 2.4% organic matter. Visual weed control was evaluated on June 7 and August 16, 2017, which was 8 and 78 DAT, respectively. Corn yields were determined on October 18, 2017 by mechanically harvesting the center two rows of each plot and adjusting grain weights to 15.5% moisture.   Introduction Acuron, Halex GT (S-metolachlor + mesotrione + glyphosate), Resicore (acetochlor + clopyralid + mesotrione), Balance Flexx, Diflexx, and Armezon Pro (topramezone + dimethenamid-P) are all competitive herbicides with different levels of preemergence and postemergence weed control. Because many of the preemergence components of these package mixes begin to decay as soon as they are applied to moist soil, it has long been known that applying part of the total load early and delaying application of the rest of the dose until later can extend control. Further, many of these premixes have postemergence activity as well, allowing for extended control with a second application. Zidua (pyroxasulfone) is a long residual herbicide with excellent preemergence control of grassy weeds and good activity on some small seeded broadleaf weeds. It was also included to augment weed control with atrazine applied preemergence alone. Postemergence glyphosate was included to help with any weeds that escaped the initial application. Therefore, it was the objective of this study to test these various compounds and their timings of application for weed control.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated sequential applications of premix herbicides for efficacy in corn. The experimental area was overseeded with kochia, Palmer amaranth, crabgrass, quinoa, and domesticated sunflower prior to corn planting. Quinoa and domesticated sunflower were used as surrogates for common lambsquarters and common sunflower, respectively. Herbicides were applied either preemergence (PRE) alone or PRE followed by postemergence (POST). All herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi. Application, environmental, crop, and weed information is shown in Table 1. Plot size was 10 × 35 feet and arranged in a randomized complete block with four replicates. Soil for the experi-ment was a Beeler silt loam with pH 7.6 and 2.4% organic matter. Visual weed control was determined on June 23 and September 5, 2017, which was 7 and 81 days after the POST treatments (DAPT), respectively. Corn yields were determined on October 23, 2017, by mechanically harvesting the center two rows of each plot and adjusting grain weights to 15.5% moisture.

Results and Discussion
Control of kochia, green foxtail, quinoa, and Palmer amaranth was 96 to 100% regardless of herbicide or evaluation date, and did not differ among treatments (data not shown). Although common sunflower control was slightly less with Acuron + atrazine applied PRE compared to other treatments at 7 DAPT (Table 2), no differences for sunflower control occurred by 81 DAPT. Crabgrass control was 95 to 100% regardless of treatment early in the season, and remained high with all herbicides except Balance Flexx + atrazine PRE followed by Diflexx + atrazine and glyphosate POST (88%). All herbicide treatments resulted in grain yields that were 67 to 101 bu/a greater than the untreated controls. The best yields were achieved when Acuron + atrazine were applied alone PRE and when Resicore + atrazine PRE was followed by Resicore + atrazine and glyphosate POST (133 to 128 bu/a). These yields were better than yields from corn receiving Balance Flexx + atrazine PRE followed by Diflexx + atrazine and glyphosate POST (99 bu/a). The best herbicide treatment yielded 34 bu/a more than the lowest yielding herbicide combination.

Introduction
Previous studies have shown that adding glyphosate, 2,4-D, or dicamba could ameliorate Vida's weakness of rapid tissue burn without significant translocation. It was unknown if such tank mixes could control older, larger weeds later in the season. Therefore, it was the objective of this study to compare tank mix Vida with glyphosate, 2,4-D, and/or dicamba for late season fallow weed control.

Experimental Procedures
An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated Vida alone and in tank mixtures for late summer weed control in fallow. All herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer calibrated to deliver 20 GPA at 30 psi and 4.2 mph. Application, environmental, and weed information is given in Table 1. The experiment was conducted on a Beeler silt loam soil with pH 7.6 and 2.4% organic matter. Plots were 10 × 35 feet and arranged in a randomized complete block with four replications. Visual control of kochia and Russian thistle was determined on September 15 and 29, and October 12, 2017, which corresponded to 8, 22, and 35 days after herbicide treatment (DAT), respectively.

Results and Discussion
Kochia control at 8 DAT was best when Vida was tank mixed with glyphosate, 2,4-D amine, and/or dicamba (Table 2), and this trend continued through 35 DAT. However, no Vida treatment controlled kochia more than 60% at 35 DAT. Treatments containing glyphosate, 2,4-D, and/or dicamba without Vida did not control kochia more than 33% at 35 DAT. Similarly, Russian thistle control was best regardless of evaluation date when Vida was applied alone or tank mixed with another herbicide, and Vida treatments provided 90 to 94% Russian thistle control at 35 DAT. Treatments without Vida controlled Russian thistle no more than 63%.

Introduction
Acuron (S-metolachlor + atrazine + mesotrione + bicyclopyrone) and SureStart II (acetochlor + clopyralid + flumetsulam) are not currently labeled for use in grain sorghum, as their potential to injure grain sorghum is unknown. Currently, it is a violation of federal law to use them for weed control in sorghum. However, they show potential for further research. Valor (flumioxazin) is currently labeled for use 30 days before planting grain sorghum provided 1 inch of rain falls prior to planting. It is not known how much injury can occur from Valor when applied 2 weeks prior to planting without rainfall, or the effects of Acuron or Surestart II on grain sorghum. Lumax EZ (S-metolachlor + mesotrione + atrazine), Bicep Lite II Magnum (S-metolachlor + atrazine), and Degree Xtra (acetochlor + atrazine) have long been used for weed control in sorghum. Therefore, it was the objective of this study to compare Acuron, SureStart II, and Valor to the known standards Lumax EZ, Bicep Lite II Magnum, and Degree Xtra.

Experimental Procedures
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, and at the Texas AgriLife Research Center near Lubbock, TX, to evaluate preplant, non-labeled herbicides for residual weed control and crop tolerance in grain sorghum. Herbicides were applied using a tractor-mounted, compressed-CO 2 sprayer delivering 20 GPA at 30 psi at Garden City and a backpack sprayer delivering 10 GPA at 32 psi at Lubbock. Application, environmental, crop, and weed information is shown in Table 1. Plot size was 10 × 35 feet at Garden City and 10 × 25 feet at Lubbock. Plots were arranged in randomized complete blocks replicated four times at both locations. Soils for the experiments were a Beeler silt loam with pH 7.6 and 2.4% organic matter at Garden City, and an Acuff loam with 0.8% organic matter and pH 7.8 at Lubbock. Weed control was visually rated on August 4 and 18, 2017, at Lubbock and Garden City and these dates were 53 and 67 days after planting (DAP), respectively. Visual sorghum injury was determined on June 13 and July 11, 2017, at Lubbock (14 and 42 DAP), and on June 29 and August 18, 2017 at Garden City (17 and 67 DAP). Sorghum yields were determined on October 19 and November 1, 2017, at Lubbock and Garden City, respectively.

Results and Discussion
Palmer amaranth control at Garden City was 90% or more with Acuron at 2.0 or 2.5 qt/a and Lumax EZ at 2.7 qt/a (Table 2). At Lubbock, Palmer amaranth control exceeded 96% with all herbicides except Surestart II at 1.5 qt/a and Valor at 1.0 oz/a. Surestart II at 1.5 qt/a and Valor at 1.0 oz/a controlled kochia 75 to 85% at Garden City, and these herbicides along with the 2 oz/a rate of Valor provided 70 to 73% Russian thistle control at Garden City. No visible sorghum injury was observed at Garden City, and sorghum yields did not differ between herbicide-treated and nontreated sorghum (Table 3). Very dry conditions during the experiment at Garden City likely minimized sorghum injury and limited sorghum yields. At Lubbock, minor sorghum injury was observed early with Acuron at either rate or Valor at 2 oz/a. By 42 DAP, only Surestart II showed sorghum injury at Lubbock. The injury with this treatment at Lubbock was also evident in sorghum yields. Sorghum receiving Surestart II yielded 36 bu/a less grain than sorghum treated with Bicep Lite II Magnum, which had the highest yield. However, all herbicide-treated sorghum at Lubbock yielded 28 to 65 bu/a more grain than nontreated sorghum. This research shows that injury from these non-labeled herbicides can vary a great deal from location to location, which suggests that it should also vary from season to season based on rainfall. Therefore, growers should avoid using these unregistered products until permitted by labeling changes.

Introduction
Sorghum is an important crop in Kansas. However, in-season weed control options for sorghum are limited. Season-long interference by Palmer amaranth exacerbates the limitation, due to PA's resistance to multiple herbicides that have different modes of action.
This 2-year study investigated the ability of a contrasting combination of cultural and chemical practices to control Palmer amaranth while maintaining or improving sorghum grain yield. Particular research emphasis was to evaluate the effect(s) of integrating half-rates of dicamba and atrazine applied as PRE with increasing sorghum density and nitrogen rate on PA control and grain yield in an irrigated environment.

Experimental Site
Field experiments were conducted at the Southwest Research-Extension Center, near Garden City, KS, in 2016 and 2017. The soil at the site was predominantly Richfield silt loam (fine, montmorillonitic, mesic Aridic Argiustoll).

Experimental Design
Three planting densities (60,000, 90,000, and 120,000 seeds/a), three nitrogen rates (0, 100, and 200 lb/a), and two in-season weed control levels (weedy vs. weed free) were evaluated for their ability to control Palmer amaranth while maintaining grain yield of sorghum using a completely randomized block design with split-split plot arrangement and four replicates. Planting density, nitrogen rate, and in-season weed control were treated as the main plot, sub-plot, and sub-sub plot factors, respectively.

Plot Establishment and Management
Experimental plots were established using a John Deere planter in a field with a natural infestation of Palmer amaranth. Each sub-sub plot was planted to 4 rows of sorghum at 22.5 ft (2016) or 35 ft (2017) long. The field was disked and field cultivated to assure a weed-free seedbed at planting. Sorghum, "DK 3707," was planted on June 20, 2016, and May 24, 2017, in rows 30 in. apart, and 0.5 lb/a dicamba tank-mixed with 2 lb/a atrazine + .25% v/v Induce (surfactant) was sprayed across all plots at the spike stage or after sorghum had sprouted, but prior to sorghum emergence to avoid potential injury from the herbicide. No other weed species but Palmer amaranth was allowed to grow within the plots to avoid unwanted sources of variation. Further, hand-pulling and hoeing were done as necessary in plots assigned for in-season weed control. Irrigation was supplied to meet 120% of crop evapotranspiration. Sorghum was harvested at physiological maturity and yields were adjusted to 13% grain moisture.

Data Collection
Yield and other parameters including sorghum height and headcount, and Palmer amaranth number, height, and biomass were estimated from the two central rows.
Only grain yield will be presented in this report.

Data Analysis
Data were analyzed using SAS version 9.3 (SAS Institute Inc., Cary, NC).

Results
Nitrogen rate and seeding rate did not affect sorghum yield independently or in combination. Controlling Palmer amaranth in plots increased sorghum yield by 50 bu/a (56%) in 2017 and 35 bu/a (32%) in 2016 ( Figure 1).

Conclusion
In both years of the study, Palmer amaranth reduced sorghum yield by an average of about 40%. Clearly, integration of greater sorghum density (>60,000 seeds/a) in conjunction with increased N rate and half rates of dicamba and atrazine is not an effective strategy to control Palmer amaranth.