Kansas Fertilizer Research 2020

A summary of research conducted in 2018-2020 on fertilizer use and management practices for crops in Kansas. Published in 2020 from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service https://www.ag.k-state.edu/.


Introduction
Tall fescue is the major cool-season grass in southeastern Kansas. Perennial grass crops, as with annual row crops, rely on proper fertilization for optimum production; however, meadows and pastures are often under-fertilized and produce low quantities of low-quality forage. The objective of this study was to determine the effect of N fertilizer timing and P and potassium (K) fertilization rates on tall fescue yields.
Fall harvest was unaffected by P rate so that the total annual production mirrored the response measured in the spring harvest. Spring harvest yield was greatest when N was applied either in late fall or late winter. Even though applying N fertilizer at the E2 growth stage in spring resulted in greater yield than with no N, delaying N application resulted in more than a 50% reduction in spring yield compared with the more traditional timings of either late fall or late winter. However, at the fall harvest tall fescue yield was greater from spring N applications compared with no N or N applied in either late fall or late winter. Thus, average annual total tall fescue yields were more than doubled by applying N. However, the differences in total yield from different N application timings were small with only late fall N application resulting in a 0.3 ton/a greater yield than applying N in the spring.
Dry conditions in 2018 resulted in low, first-year tall fescue yields at Site 2 (Table 2). Tall fescue yield was greater with 50 or 100 lb P 2 O 5 /a than with no P, but the average differences were less than 0.2 ton/a. Phosphorus fertilization rates had no effect on the fall or total harvest yields. Spring tall fescue yield was greatest with late fall fertilization. However, as for the first year at Site 1 (Table 1), both late fall and late winter N fertilization in the first year at Site 2 resulted in greater spring yield than with no N or N applied at the E2 growth stage in spring (Table 2). In contrast to results from Site 1 (Table 1), spring N application did not result in greater fall yield than with no N and only yielded 0.19 to 0.24 ton/a more than with late fall or late winter fertilization (Table 2). At Site 2, the first-year tall fescue yield rank as affected by N fertilizer timing was late fall>late winter>spring>no N.      The 100 lb P 2 O 5 /a rate was only applied at the beginning of the study (Fall 2017).

Tillage and Nitrogen Placement Effects on Yields in a Short-Season Corn/Wheat/ Double-Crop Soybean Rotation Introduction
Many crop rotation systems are used in southeastern Kansas. This experiment is designed to determine the long-term effect of selected tillage and N fertilizer placement options on yields of short-season corn, wheat, and double-crop soybean in rotation.

Experimental Procedures
A split-plot design with four replications was initiated in 1983 with tillage system as the whole plot and N treatment as the subplot. In 2005, the rotation was changed to begin a short-season corn/wheat/double-crop soybean sequence. Use of three tillage systems (conventional, reduced, and no-till) continued in the same whole plots as the previous 22 years. The conventional system consisted of chiseling, disking, and field cultivation. Chiseling occurred in the fall preceding corn or wheat crops. The reduced-tillage system consisted of disking and field cultivation prior to planting. Glyphosate was applied to the no-till areas prior to planting. The four N treatments for the crop were: no-N (control) and N fertilizer placement as broadcast, dribble (surface band), and knife (subsurface band at 4 inches deep) UAN (28% N) solution. The N rate for the corn crop grown in odd-numbered years was 125 lb/a. The N rate of 120 lb/a for wheat was split as 60 lb/a applied pre-plant as broadcast, dribble, or knifed UAN. All plots except for the no-N controls were top-dressed in the spring with broadcast UAN at 60 lb/a N.

Results and Discussion
In 2018, tillage system did not affect wheat yield (Table 1). Overall, fertilizing with N quadrupled wheat yield. Preplant N application by knifing resulted in 10% greater wheat yield than with broadcast, with dribble application resulting in intermediate yields.
The average yield of soybean planted doublecrop after wheat harvest was nearly 50 bu/a in 2018 and no-till was about 10% greater than with tillage. There was no residual effect on soybean yields from N applied by different pre-plant methods to the previous wheat crop.

Pre-Plant Nitrogen Rate and Application Method and Side-Dress Nitrogen Rate Effects on Corn Grown No-Till on a Claypan Soil Introduction
Environmental conditions vary widely in the spring in southeastern Kansas. As a result, much of the N applied prior to corn planting may be lost before the time of maximum plant N uptake. Pre-plant N application method, pre-plant N rate, and side-dress N rate selection to provide N during rapid growth periods may improve N use efficiency while reducing potential losses to the environment. The objective of this study was to determine the effect of timing of pre-plant and side-dress N fertilization options on corn grown on a claypan soil.

Experimental Procedures
The experiment was established in spring 2018 on a Parsons silt loam soil at the Parsons Unit of the Kansas State University Southeast Research and Extension Center that had been in continuous no-till for more than 10 years. The experiment was a factorial arrangement of a randomized complete block design with four blocks (replications). The two factors were pre-plant N fertilizer placement of broadcast and knife (subsurface band at 4 inches deep) and pre-plant/side-dress N rates of 0-0, 0-150, 100-0, 100-50, 100-100, 150-0, 150-50, 150-100, and 200-0 lb/a. Side-dress applications were broadcast at the V10 growth stage using 7-stream pattern fertilizer nozzles. The N source for all treatments was liquid urea-ammonium nitrate (UAN; 28% N) fertilizer. Pre-plant N fertilizer was applied on March 12, 2018, and side-dress N was applied at V10 on June 4, 2018, to appropriate plots. Corn was planted on April 10 and harvested on August 28, 2018.

Results and Discussion
Even though individual yield components were not significantly affected by pre-plant N application method, general trends resulted in more than 5 bu/a greater corn yields when N was knife applied rather than broadcast prior to planting (Table 1). In general, applying N at any rate and time resulted in approximately 50% greater corn yield in 2018 than the 75.6 bu/a in the no-N control. However, there were few differences in yield among the eight treatments receiving N fertilizer. For example, general increases in total N applied, as well as applying no N until the V10 growth stage (0-150 lb/a pre-plant/side-dress N rate), had little effect on yield in 2018. Stand was not affected by pre-plant/side-dress N rates, but fertilizing with N increased kernel weight, the number of ears/plant, and the number of kernels/ear compared with corn grown in the no-N control.

Introduction
Increased fertilizer prices in recent years-especially noticeable when the cost of phosphorus spiked in 2008-have led U.S. producers to consider other alternatives, including manure sources. The use of poultry litter as an alternative to fertilizer is of particular interest in southeastern Kansas because large amounts of poultry litter are imported from nearby confined animal feeding operations in Arkansas, Oklahoma, and Missouri. Annual application of turkey litter can affect the current crop, but information is lacking concerning any residual effects from several continuous years of poultry litter applications on a following crop. This is especially true for tilled soil compared with no-till because production of most annual cereal crops on the claypan soils of the region is often negatively affected by no-till planting. The objective of this study was to determine if the residual from fertilizer and poultry litter applications under tilled or no-till systems affects soybean yield and growth.

Experimental Procedures
A water quality experiment was conducted near Girard, KS, on the Greenbush Educational facility's grounds from spring 2011 through spring 2014. Fertilizer and turkey litter based on rates of 120 lb N/a and 50 lb P 2 O 5 /a were applied prior to planting grain sorghum each spring. Individual plot size was 1 acre. The five treatments, replicated twice, were: 1. Control: no N or P fertilizer or turkey litter -no tillage; 2. Fertilizer only: commercial N and P fertilizer -chisel-disk tillage; 3. Turkey litter, N-based: no extra N or P fertilizer -no tillage; 4. Turkey litter, N-based: no extra N or P fertilizer -chisel-disk tillage; and 5. Turkey litter, P-based: supplemented with fertilizer N -chisel-disk tillage.
1 Starting in 2014 after the previously-mentioned study, soybean was planted with no further application of turkey litter or fertilizer. Prior to planting soybean, tillage operations were done in appropriate plots as in previous years. A sub-area of 20 × 20 ft near the center of each 1-acre plot was designated for crop yield and growth measurements. Samples were taken for dry matter production at V3-V4 (approximately 3 weeks after planting), R2, R4, and R6 growth stages. Yield was determined from the center 4 rows (10 × 20 ft) of the sub-area designated for plant measurements in each plot.

Results and Discussion
In 2018, the residual effects of turkey litter and fertilizer amendments affected soybean yield, stand, pods/plant, and dry matter production ( Table 1). The two treatments which had previously received a high application rate of turkey litter based on N requirements, regardless of tillage system, resulted in greater yields than from plots that had received low rates of turkey litter (P-based), commercial fertilizer, or no fertilizer N or P. The number of pods/plant were greater where N-based turkey litter had been applied in no-till than where fertilizer, a low rate of turkey litter, or no fertilizer or litter had been applied. In addition, stand was slightly improved where fertilizer or the high rates of turkey litter had been applied. The effect of residual treatments on soybean dry matter production was sporadic. However, by R6, dry matter production was greater where turkey litter had previously been applied on an N-basis (high rate) than on a P-basis (low rate), with dry matter from the fertilizer treatment being intermediate.  Control, no turkey litter or N and P fertilizer with no tillage; TL-N, N-based turkey litter application with no tillage; TL-N-C, N-based turkey litter application incorporated with conventional tillage; TL-P-C, P-based turkey litter application and supplemental N application incorporated with conventional tillage; and Fert-C, commercial fertilizer incorporated with conventional tillage.

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 Unit of the Kansas State University Southwest Research-Extension Center. Fertilizer treatments initiated in 1961 were N rates of 0, 40, 80, 120, 160, and 200 lb/a N 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. All fertilizers are broadcast by hand in the spring and incorporated before planting. The soil is a Ulysses silt loam. Grain sorghum (Pioneer 85G46 in 2010-2011, Pioneer 84G62 in 2012-2014, Pioneer 86G32 in 2015, Pioneer 84G62 in 2016-2017, and Pioneer 85P44 in 2018 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 ).

Results
Grain sorghum yields in 2019 were 3% lower than the 10-year average (Table 1). Nitrogen alone increased yields by 66 bu/a while P alone increased yields 6 bu/a. However, N and P applied together increased yields up to 85 bu/a. Averaged across the past 10 years, N and P applied together increased yields up to 78 bu/a. In 2019, 40 lb/a N (with P) produced about 74% of maximum yield, which is less than the 10-year average of 83%. The 10-year average for 80 lb/a N (with P) and 120 lb/a N (with P) was 93 and 94% of maximum yield, respectively. Sorghum yields were not affected by K fertilization, which has been the case throughout the study period.
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 ~0.7 lb/bu. Maximum N removal (lb/a) was obtained with 160 lb N/a or greater with P. Similar to N, average P concentration increased with P application but decreased with higher N rates. Grain P content (lb/bu) of ~0.15 lb P/bu (0.34 lb P 2 O 5 /bu) was similar for all N rates when P was applied. Grain P removal was similar for all N rates of 40 lb/a or greater with P removal ranging from 19 to 22 lb/a. Average K concentration (%) and content (lb/bu) tended to decrease with increased N rates. Similar to P, K removal was similar for all N rates of 40 lb/a or greater plus K ranging from 22 to 26 lb/a. At the highest N, P, and K rate, apparent fertilizer recovery in the grain was 31% for N, 65% for P, and 38% for K.

Acknowledgment
The International Plant Nutrition Institute provided financial support for this research project.

A.J. Schlegel and H.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 2019, N applied alone increased yields by 71 bu/a, whereas P applied alone increased yields by 10 bu/a. Nitrogen and P applied together increased yields up to 131 bu/a, which is 10 bu/a less than the 10-year average of 141 bu/a. Application of 120 lb/a N (with highest P rate) produced 97% of maximum yield in 2019, which is slightly greater than the 10-year average. Application of 80 instead of 40 lb P 2 O 5 /a increased average yields by 4 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 41% and apparent fertilizer phosphorus recovery in the grain (AFPR g ) was 60%.

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 were 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 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 ). Grasshoppers were treated by aerial application of insecticide.

Results
Corn yields in 2019 were only 2% higher than the 10-year average (Table 1). Nitrogen alone increased yields 71 bu/a, whereas P alone increased yields 7-10 bu/a. However, N and P applied together increased corn yields up to 131 bu/a. Maximum yield was obtained with 200 lb/a N with 80 lb/a P 2 O 5. Corn yields in 2019 (averaged across all N rates) were 4 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. Nitrogen removal (lb/a) was greater at the higher yield levels. Maximum N removal (116 lb/a), was attained with 200 lb N and 80 lb P 2 O 5 /a. At the highest N and P rate, AFNR g was 41% and AFPR g was 60%. 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.

Acknowledgment
The International Plant Nutrition Institute provided financial support for this research project.
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.        Table 2. Nitrogen (N) and phosphorus (P) fertilization on grain N and P content of irrigated corn, Tribune, KS, 2010-2019

Summary
The objective of this study was to investigate the effect of different tillage systems and nitrogen (N) fertilizers on corn yield. Higher corn yields (207 bu/a and 203 bu/a) were found under no-tillage + high (150 lb N/a) manure application, and tillage + super high manure (750 lb N/a), respectively. The trend observed for the different nitrogen fertilizers between tillage systems was the same. However, a greater corn yield was observed under no-till in comparison to tilled conditions for both high fertilizer and high manure. No-till improves soil water infiltration, aggregation, nutrient cycling, and may increase crop yield. On other hand, soil erosion, runoff, and a depreciated plant stand may have been the reasons for lower yields under tillage for some of the treatments. Overall, the addition of organic fertilizer associated with no-till was a better practice for increasing corn yield compared to the use of mineral fertilizer associated with or without tillage.

Introduction
Long-term experiments are essential to understand how corn yield is affected by different agricultural practices and to make management decisions associated with cropping system performance (Richter et al., 2007). Such experiments are critical for corn producers because replacing chisel plow with no-till (NT) practices is a cultural change driven by multiple factors including markets, weather cycles, agribusiness, and scientific advances (Coughenour and Chamala, 2000). Economically, NT is attractive because individual tillage events are eliminated, thus reducing machinery fuel, energy, and maintenance costs (Lal et al., 2007). No-till can also affect crop productivity (Daigh et al., 2018) and improve several soil properties, such as soil organic carbon (Nicoloso et al., 2018), soil aggregation (Fabrizzi et al., 2009), bulk density (Blanco-Canqui et al., 2009), and soil microbial community (Smith et al., 2016), thus improving soil health. Organic waste and organic fertilizer, such as cattle manure, may replenish and maintain soil nutrient equilibrium, thus increasing nutrient status and perhaps crop yield. The objective of this study was to investigate the effect of different long-term tillage systems and different nitrogen (N) fertilizers on corn yield.

Procedures
This study was based on a long-term (31 years) experiment established in 1990 at the Kansas State University Department of Agronomy North Farm in Manhattan, KS (39° 12′ 42"N, 96° 35′ 39"W). The local mean annual precipitation and potential evapotranspiration were 31.5 and 51.2 inches, respectively, with a mean annual temperature of 11.4°C. The soil was a moderately well-drained Kennebec silt loam (fine-silty, mixed, superactive mesic Cumulic Hapludoll). Prior to the establishment of the experiment, the area was used for small grain production (wheat, oats, and other C3 crops) under intensive tillage for at least 60 years. The experiment was initiated in 1990 when corn (Zea mays L.) was first introduced at this site. The tillage systems were fall chisel plow with pre-plant spring offset disk (chisel tillage: T) and no-till (NT) by planting directly through the crop residues with minimal soil disturbance. The chisel plow and disking operations were performed to a depth of 6 and 4 inches, respectively. The fertilization treatments were different N fertilizers applied just before planting: 1) 750 lb N/a of available N as organic fertilizer, super high manure (SHM); 2) 150 lb N/a of available N as mineral fertilizer (urea, HF); 3) 150 lb N/a of organic N fertilizer (HM); 4) 75 lb N/a of available N as mineral fertilizer (urea, LF); 5) 75 lb N/a of organic N fertilizer (LM); and 6) a control without N (C). Mineral fertilizer was broadcast-applied and left on the surface for NT, and incorporated at 2-4 inches for T. The organic fertilizer was composted organic waste collected at the North Farm's composting facility and consisted of a mixture of food waste, hay waste, and cattle manure. The organic fertilizer was analyzed for total N, organic N, NH 4 + and NO 3 − and the application rate was calculated assuming that 30% of organic N and 100% of mineral N was available during the crop growing season. The corn (hybrid DKC-35RIB, VT2PRIB) was planted at a seeding rate of 28,000 seeds/a, using 30 inches row spacing, on May 17, 2019. To evaluate corn yield, corn ears from the middle 2 rows at 30-ft length of each plot were hand-harvested on October 18, 2019. The corn grain was adjusted to 15.5% moisture for yield calculation.
The treatments were arranged as a split-plot in randomized complete block design with four replications. Tillage treatments (NT and conventional tillage) were considered the main plot and the N fertilizers were considered the subplot. The effect of tillage, fertilizer, and their respective interaction (fixed effects) on corn yield (response variable) were analyzed by ANOVA with a mixed model. Random effects corresponded to the block (replication) and tillage within block. A pairwise comparison was used to determine significant differences among treatments for all the fixed effects presenting a significance equal or lower than 0.05 using the Fisher's least significant difference (LSD) (R Core Team, 2017).

Results
A significant two-way interaction (P = 0.009) was found for tillage × fertilizer. Higher corn yield was found under NT-HM (207 bu/a) and T-SHM (203 bu/a), respectively ( Figure 2). The trend observed for the N fertilizers between tillage systems was the same. However, greater corn yield was observed under no-till compared to tilled conditions for both high fertilizer and high manure. Plant stand was not evaluated in this study; however, fewer plants were observed in some of the T plots after several precipitation events (Figure 3a and 3b). Thus, corn yield under T treatments may have been affected by the lower number of final plants in the plots (Figures 3c and 3c). According to Mikha and Rice (2004), NT improves soil properties, such as soil organic matter, aggregate stability, and water holding capacity, which help maintain land productivity compared to intensively tilled soils. Moreover, NT increases water infiltration and reduces soil erosion, runoff, and raindrop impact on the soil surface due to physical protection from the crop residue. Crop residue maintains soil moisture and reduces soil temperature during warm periods, providing a more stable environment for plant and root growth. No differences were found when comparing C, SHM, LF, and LM within tillage systems.
Compost (HM) produced 17% more grain than HF, 190 bu/a and 157 bu/a, respectively. The same was found for LM and HM, where LM produced 30% more than LF, 170 bu/a and 120 bu/a, respectively. It is well known that besides N, organic amendments also provide organic carbon, phosphorus, potassium, and micronutrients, such as zinc, boron, and manganese to the plant. Moreover, an increase in soil organic matter increases micronutrient uptake (Dhaliwal et al., 2019). Overall, the addition of organic fertilizer associated with no-till was a better practice for increasing corn yield compared to the use of mineral fertilizer associated with or without tillage.

Summary
Winter wheat is often double-cropped after soybeans in no-tillage systems. The soybean crop removes large quantities of sulfur (S), which might cause S deficiency for the following wheat crop. Our objective was to evaluate the responses of three wheat varieties to three nitrogen (N) and four S fertilizer rates representing a range of N:S ratios. The experiment was conducted near Ashland Bottoms and Hutchinson, KS. Treatments were arranged as a complete factorial structure with a split-split-plot design.
Variety was the whole-plot, N was the sub-plot, and S was the sub-sub plot. Nitrogen rates were 50, 100, and 150% of the university recommendations for a 60 bushel per acre yield, and S rates were 0, 10, 20, and 40 pounds of S per acre. Wheat varieties evaluated were Zenda, SY Monument, and LCS Mint. Increasing the N rate increased grain yield at both locations. Sulfur increased grain yield at Ashland Bottoms but not at Hutchinson. Nitrogen by S interaction occurred for protein concentration at both locations. At Hutchinson, N rates of 50, 100, and 150% N resulted in grain yield of 62, 73, and 78 bu/a. For the 50% and 100% N rate, protein concentration was 10.8% and 11.3%; however, the 150% N rate with 20 or 40 lb S/a increased protein concentration to 11.8% as compared to 11.5% observed in the 0 or 10 lb S/a treatments. At Ashland Bottoms, N rates of 50, 100, and 150% resulted in grain yield of 56, 69, and 74 bu/a across S treatments. For the 0 pounds of S per acre treatment, though, these N rates resulted in grain yields of 36, 42, and 40 bu/a. The 150% N rate with 20 and 40 lb S/a increased grain yield by 5 bu/a as compared to the 10 lb S/a treatment. At the 50% N rate, protein concentration was 9.7% with an application of S as compared to 10.3% for the 0 lb S/a, which is due to a dilution effect from the increased grain yield. As S application increased, protein concentration decreased at the 100% N rate. However, at the 150% N rate, protein concentrations were 12.2, 11.5, 11.8, and 11.9% for the 0, 10, 20, and 40 lb S/a, respectively. Our results suggest that a balanced fertilization of N and S are essential for improving yield and protein concentration in no-till systems following soybeans, and that initial S in the profile and soil organic matter (OM) play a crucial role in determining the crop's response to the added fertilizers.

Introduction
Sulfur plays many roles within the plant, including the synthesis of amino acids, formation of disulfide linkages, glucoside oils, and chlorophyll (Taiz and Zierger, 2010). Sulfur is supplied to plants through rainfall, mineralization of the soil's OM and crop residue, or as part of organic or mineral fertilizers. The Clean Air Act was successful in decreasing the emission of SO 2 to the atmosphere within the continental USA, which in turn, reduced atmospheric S deposition from about 13 to about 3.5 pounds of sulfur per acre per year (Sullivan et al., 2018). While this is a success story in reducing environmental pollution, rainfall has historically been an important supplier of S to growing crops. The reduction in S deposition in the rainfall, coupled with increased crop removal and other factors (e.g., decreased use of manure as a fertilizer and decreased S content of traditional fertilizers) has increased S deficiency in many wheat-growing regions (Kaiser et al., 2019). Particularly in Kansas, where winter wheat planted after soybeans has become the preferred crop rotation in recent years for many producers (Lollato et al., 2019a), the issue seems to be severe as a 60 bushel per acre grain soybean crop removes approximately 25 pounds of S in the grain and stover (Lamond, 1997).
The high removal of S by soybeans, coupled with lower organic matter mineralization in the spring and reduced S deposition in the rainfall, resulted in increasingly common symptoms of S deficiency in the wheat crop. While the S requirements of wheat are generally low [i.e., an 80 bushel per acre crop needs about 22 pounds of S to complete its cycle, (Lamond, 1997)], recent evidence suggests that depending on the S content of the soil, wheat can be S-limited at these yield levels when mineral fertilizer is not supplied (Jaenisch et al., 2019).
Because co-limitation and stoichiometry between N and S can explain the crop responses to both fertilizers (Carciochi et al., 2020), it is important to study S effects on the wheat crop within the context of N fertility. Proper N fertilization ensures a high tiller number and grain yield in wheat (Lollato et al., 2019b), which is generally sink-limited, and kernel per foot acts as coarse regulator of grain yield (Lollato and Edwards, 2015). Potential kernel per foot is determined by Feekes 6 in the winter wheat growing season, and N deficiency at this time will result in decreased yield potential. Thus, matching N application with this critical growth stage is important for maximizing kernels per foot (de Oliveira Silva et al., 2020a). Likewise, N concentration within the plant changes throughout the growing season according to biomass levels; thus, N dilution curves help determine N deficiencies in crops (de Oliveira Silva et al., 2020b).
Research is needed to determine the optimal N concentration and N:S ratios in plant tissue to maximize grain yield and quality in Kansas. Thus, our objectives were to evaluate the effects of S and N fertility and their interactions with winter wheat variety on grain yield and grain protein concentration.

Procedures
The experiment was established at the South-Central Experiment Field in Hutchinson (fine-loamy, Ost loam) and the Agronomy Farm in Ashland Bottoms, KS. Both locations were managed under rainfed conditions and were chosen as no-till wheat is commonly sown into soybean stubble. A three-way factorial experiment was arranged in a split-split-plot design with four replications. The varieties SY Monument, LCS Mint, and Zenda, selected for their differences in N use efficiency, were the whole plot. Three N rates (i.e., 50, 100, and 150% of the N needed for a 60 bushel per acre yield goal considering the soil N profile analyses for each location) were the sub-plot and were applied using urea ammonium nitrate (UAN, 28-0-0). The N rates for 50, 100, and 150% of the yield goal were 66, 127, and 189 lb N/a and 52, 102, and 153 lb N/a for Ashland and Hutchinson, respectively. Four S rates were the sub-sub-plot, in which S was applied as ammonium thiosulfate (12-0-0-26S) at 0, 10, 20, and 40 lb S/a. A pressurized CO 2 back sprayer with a three-nozzle spray boom applied both the N and S. The specific streamer nozzles (SJ3-02-VP -SJ3-05-VP) varied due to the change in N and S rates. The N and S were applied in combination for specific treatments and application occurred at Feekes 4. The UAN rates were adjusted to balance the N application for treatments receiving ammonium thiosulfate.
Wheat was sown no-till into soybean stubble directly after harvest with a Great Plains 506 no-till drill (7 rows spaced at 7.5 inches) with plot dimensions of 4.375-ft wide × 30-ft long at all locations. Seed was treated with 5 oz Sativa IMF Max across the whole study so neither fungicide nor insecticide were a limiting factor. Likewise, the three varieties were sown at 1.5 million seeds/a due to the later sowing date. Soil samples were collected at sowing at each location for soil nutrient analysis at two depths i.e., 0-6 in. and 6-24 in. (Table 1). A total of 15 cores were pulled per depth and combined to represent a composite sample at each location. Weeds were controlled to ensure they were not limiting factors by a pre-and post-emergence herbicide application. Insect pressure was not experienced in 2018-2019.

Weather
The 2018-2019 winter wheat growing season had a cold and wet winter, a cold and wet early spring, and a cool and wet late spring/early summer. The wet and cool temperatures kept the wheat crop dormant until late April. Likewise, the cool spring and increased rainfall reduced spring tillering but incorporated the applied fertilizer. Grain harvest occurred very late due to the cool and wet weather. These conditions resulted in above-average grain yields at both Ashland Bottoms and Hutchinson.

Initial Soil Profile
Initial soil test results varied greatly for Ashland Bottoms and Hutchinson (Table  1). The soil at Ashland Bottoms had lower organic matter content and sulfate-S as compared to Hutchinson. A significant amount of sulfate-S comes from OM mineralization and this mineralization can be sufficient enough to avoid yield losses from S deficiencies. Based on the soil test results, Ashland Bottoms and Hutchinson had a supply of 10 and 17 lb of S/a, respectively. Thus, while Ashland Bottoms was severely deficient in S; Hutchinson had sufficient S depending on the yield level of the crop.

Wheat Grain Yield
Across locations, increasing N rates increased wheat grain yield (Figure 1). At Hutchinson, N rate was the only significant effect and N rates of 50, 100, 150% N resulted in grain yield of 62, 73, and 78 bu/a, respectively ( Figure 1). Grain yield did not respond to S application at Hutchinson. At Ashland Bottoms, there was a significant N by S interaction-the absence of S resulted in grain yields of about 40 bushels per acre, regardless of N rate. However, when S fertilizer was applied, grain yield increased to the 60-85 bushels per acre range and became responsive to N. Interestingly, when 10 pounds of S per acre was provided, wheat grain yield increased from 50 to 100% N, and plateaued afterwards. Nonetheless, providing 20 or 40 pounds of S per acre allowed grain yields to respond linearly to increases in N rates to as much as 150% N. At this rate, 20 and 40 pounds of S per acre increased grain yield by 5 bu/a as compared to the 10 pounds of S per acre.

Grain Protein Concentration
There was a significant N by S interaction on grain protein concentration, as well as a significant variety effect, at both locations. First, there was an overarching trend of increased protein concentrations with increased N rates at both locations. At Ashland Bottoms, the significant interaction resulted from the tendency to stabilize protein concentrations for N rates beyond 100% for the 0 and 10 pounds of S per acre treatments, while 20 and 40 pounds of S per acre allowed protein concentrations to continue to increase with increases in N rate. Specifically, at the 50% N rate, protein concentration was 9.7% with an application of S (regardless of S rate) as compared to 10.3% for the 0 lb of S. As sulfur application increased, protein concentration decreased at the 100% N rate. However, at the 150% N rate, protein concentration was 12.2, 11.5, 11.8, and 11.9% for the 0, 10, 20, and 40 pounds of S per acre. Zenda had a protein concentration of 11.4%, which was greater than SY Monument and LCS Mint. At Hutchinson, the trends were not as clear as at Ashland Bottoms, but likewise, protein concentrations increased with N rates, and the 20 and 40 pounds of S per acre resulted in the highest protein concentrations at high N rates. Specifically, at the 50% and 100% N rate, protein concentration was 10.8% and 11.3%, respectively. However, the 150% N rate with 20 or 40 lb S/a increased protein concentration to 11.8% as compared to 11.5% for the 0 or 10 lb S/a. Following the same trend as that measured at Ashland Bottoms, Zenda had protein concentration of 11.8%, which was greater than SY Monument and LCS Mint.

Preliminary Conclusions
Due to limitations of sites and years, it is difficult to make strong conclusions out of a single year of data. However, the significant N by S rate interactions for both grain yield and protein concentration suggest that a balanced nutrition is needed for both nutrients to produce high yields. One trend that surfaced was that increasing N increased grain yield and protein concentration, suggesting that N rates can be further increased to maximize yield (depending on yield potential). Increasing the S rate to 20 lb per acre maximized wheat yield at Ashland Bottoms; however, no grain yield response to S rate was measured at Hutchinson. Thus, these results suggest that soil profile S plays an important role in maximizing wheat yield, as the soil at Ashland Bottoms was at deficient levels as compared to the soil at Hutchinson. We will evaluate the plants' tissue nutrient concentration for co-limitations and stoichiometry to further decipher this interaction of N by S within wheat plants.   Fertility levels include soil pH, buffer pH, Mehlich-3 extractable phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), ammonium-(NH 4 -N) and nitrate-nitrogen (NO 3 -N), chloride (Cl), sulfate-sulfur (SO 4 -S), organic matter (OM), and cation exchange capacity (CEC). Sampling depths were 0-6 in. and 6-24 in.    In-season measurements included flag leaf N concentration, grain yield, yield components, and grain protein concentration. Flag leaf N concentration ranged from 2.4 to 4.1% across all environments and treatments, and increases in N rates increased flag leaf N concentration linearly. Grain yield ranged from 36.3 to 94.4 bu/a and increased with increases in N rate usually following quadratic relationships at all locations except for Belleville, where no response was observed, likely due to the high organic matter levels. Grain protein concentration ranged from 11 to 15% across all locations and treatments and increases in N rates increased grain protein concentration following a usually linear relationship; however, the quadratic yield response to N rate, coupled to the linear protein response to N rate, indicated that greater N rates might be needed to maximize protein as compared to maximizing yields. Both relative grain yield and relative grain protein concentration variables calculated relative to the maximum in each respective environment, were related to flag leaf N concentration in a linear-plateau way, suggesting that flag leaf N concentration could be used as a diagnostic tool for crop N status.

Introduction
Nitrogen is a critical component of different amino acids and proteins needed to complete a plant's life cycle; thus, it is an essential element to crops (Taiz and Zieger, 2010). About 80% of total wheat N uptake occurs by anthesis (Waldren and Flowerday, 1979). Total N uptake at maturity depends on yield level and ranges from near zero to about 360 lb N/a (de Oliveira Silva et al., 2020a). Different aspects of N management (i.e., rate and timing) are among the leading causes behind the large yield gap in Kansas (de Oliveira Silva et al., 2020b;Lollato et al., 2019a), which is estimated at about 50% (Lollato et al., 2017). The exception to this rule is when the system is already saturated by N. In these cases, no response to N rate usually occurs and other factors, such as fungicide and seeding rate, become prevalent (Jaenisch et al., 2019). A recent comprehensive synthesis of long-term experiments conducted in the region suggested that wheat grain yield and grain protein concentration responses to N rate depended on yield environment (Lollato et al., 2019b). In other words, while there were limited yield responses to increases in N rate at low yield environments, yield followed a quadratic response to N rate in medium, high, and very high yield environments, with an agronomic optimum N rate increasing with increases in yield environment. Higher yield environments resulted in lower protein concentrations, as expected (Lollato and Edwards, 2015), and protein concentration increased linearly with increases in N rate.
Due to the importance of N management to wheat yield and protein, the objectives of this project were to assess winter wheat grain yield, grain protein concentration, flag leaf nitrogen concentration, and yield components as affected by different nitrogen rates in the state of Kansas during the 2018-2019 growing season.

Procedures
Field experiments were conducted during the 2018-2019 winter wheat growing season in different locations across Kansas: Ashland Bottoms, Belleville, Great Bend, Hutchinson, and Manhattan. At all locations, plots were comprised of seven 7.5 in.-spaced rows wide and 30-ft long, for a total plot area of approximately 131 ft 2 . A total of four treatments resulting from four N rates were evaluated in each location. The fertility treatments evaluated consisted of 0, 50, 100, and 150 lb N/acre applied as urea during the fall. Planting, harvest, and product application dates are provided in Table 1. The same wheat variety (Zenda) was evaluated at all locations. Harvest occurred using a Massey Ferguson XP8 small-plot, self-propelled combine. Plot ends were trimmed at harvest time to avoid border effect, and the portion harvested for grain was approximately 100 ft 2 at both locations, comprising the central portion of the plots.

Measurements and Statistical Analyses
A total of 15 individual soil cores (0 to 24-in. depth) were collected from each location and divided into 0-6 in. and 6-24 in. increments for initial fertility analysis. The individual cores were mixed to form one composite sample, which was later analyzed for base fertility levels (Table 2).
Measurements included flag leaf N concentration taken at heading (approximately 40 flag leaves were collected per plot); a 0.19 m 2 biomass sample retrieved at harvest maturity from which we measured yield components (aboveground biomass, harvest index, head number per area, kernels per head, kernels per area, and 1000-kernel weight); and grain yield, grain test weight, and grain protein concentration. Nitrogen removal in the grain was calculated using a 5.7 conversion factor from protein to nitrogen in the wheat grain, and multiplying grain N by grain yield.
Statistical analysis of the data collected in this experiment was performed using PROC GLIMMIX procedure in SAS v. 9.4 (SAS Inst. Inc., Cary, NC). Replication was treated as a random effect in the analysis for individual locations, while location and replication nested within location were random effects in the analysis across locations.

Weather Conditions
The 2018-2019 winter wheat growing season in Kansas was characterized by below average temperatures and above average precipitation (Table 3). The fall had anywhere from 9.3 to 13.9 inches of precipitation in the studied locations, sometimes resulting in poor stand establishment across the state. Due to this excessive fall precipitation and its consequent waterlogging, the Great Bend location was abandoned. The studied locations received anywhere from 16.3 to 24.9 inches of precipitation during the spring (April until July) which, coupled with below average temperatures, extended the growing season and delayed harvest until early to mid-July. Table 4 shows the results from the analysis of variance for each location individually, as well as for the combined analysis across locations. At the 0.1 probability level, nitrogen rate was a significant effect for most of the measured parameters at Ashland Bottoms, followed by Manhattan, Hutchinson, and finally the least responsive location to N rate was Belleville. The combined analysis showed a significant N rate effect on all but three measured parameters (Table 4).

Grain Yield and Yield Components
Across all treatments and locations, grain yield ranged from 36.3 to 94.4 bu/a. The lowest yielding location was Ashland Bottoms (average yield: 47 bu/a) and the highest yielding location was Belleville (average yield: 88 bu/a). At all locations except for Belleville, grain yield increased with increases in N rate (Table 5), usually following quadratic relationships (increasing until about 100 lb N per acre and plateauing at greater N rates) although in some instances, the relationship was linear. The lack of a significant N rate effect at the Belleville location could result from high levels of organic matter in this location, releasing organic nitrogen during the cycle of the crop ( Table 2).
The ANOVA results for the yield components are shown in Table 6. Overall, the yield components most often impacted by N rate were shoot biomass and 1000-kernel weight, although in some locations there were also significant effects on heads per area and kernels per area. Biomass ranged from 5116 to 14,262 lb/a, and usually increased with increased N rates (Table 6). Harvest index ranged from 0.39 to 0.46 and was not impacted by the treatments evaluated. Heads per square foot ranged from 44 to 83 and increased with increasing N rates in the combined analysis (although the individual site-year analysis failed to detect significant treatment effects). At a few sites, increasing N rate reduced 1000 kernel weight, which is probably explained by more kernels being produced due to more N, and thus, additional smaller/secondary kernels originated. Increases in N rate generally increased kernels per area.

Flag Leaf N Concentration, Grain Protein Concentration, and Grain Test Weight
Flag leaf N concentration ranged from 2.4 to 4.1% across all environments and treatments, and it was significantly affected by N rate at Ashland Bottoms, Belleville, Manhattan, and in the combined analysis (Table 7). Usually, increasing N rates increased flag leaf N concentration (c.a., 2.9% in the zero-N control versus 3.28% in the 150 lb N/a). Across all sources of variation, a linear plateau model explained the rela-tionship between relative grain yield (calculated in each location relative to the maximum yield in that respective location) and flag leaf N concentration with an overall robustness of r 2 = 0.26. This model suggested that relative yield increased from ~0.5 at flag leaf N of 2.4%, to 0.84 at flag leaf N of 2.97%, and plateaued afterwards for flag leaf N concentration as high as 4.1% (Figure 1).
Grain protein concentration ranged from 11 to 15% across all locations and treatments. Nitrogen rate had a significant effect on grain protein concentration at all locations, including the combined analysis (Table 7). Increasing N rates increased grain protein concentration usually in a linear way (Ashland Bottoms, Manhattan, and combined analysis), but sometimes the relationship tended to reach a plateau or quadratic relationship in which there was no increase in protein concentration beyond a given N rate (Belleville and Hutchinson). Similarly to relative grain yield, relative grain protein concentration (calculated by location relative to the maximum respective to each location) was related to flag leaf N concentration (r 2 = 0.23) and followed a linear-plateau shape ( Figure 1). Relative grain protein concentration increased from about 0.75 at flag leaf N concentration of 2.4%, to 0.94 at flag leaf N concentration of 2.95%. Further increases in flag leaf N concentration did not increase relative grain protein content.
Grain test weight ranged from 57.3 to 64.2 pounds per bushel across all treatments and locations. There were significant N rate effects on test weight in Hutchinson and Manhattan, as well as in the combined analysis. At these locations, test weight tended to decrease with increases in N rate, likely because greater N rates originated more tillers and these secondary tillers usually are later and result in lighter kernels (although this was not measured in the current study).

Preliminary Conclusions
Winter wheat response to N rate is dependent on environmental conditions, including not only the weather experienced in the season (and thus the potential yield of the season), but also the amount of inorganic nitrogen made available through the soil. In this research, most of the yield response to N rate was quadratic, suggesting that the 100 lb N/a rate was sufficient to maximize yields at the yield environments here studied (though small site-to-site variations were reported). Protein tended to follow a more linear response, perhaps suggesting that more N is needed to maximize protein as compared to yield. The linear-plateau relationship developed between relative grain yield or relative grain protein as affected by flag leaf N concentration provides preliminary evidence for using flag leaf N as an in-season diagnostic tool for crop N status.

Introduction
Historically, N fixing microbes have had little to no role in agronomy outside of those in symbiotic association with legumes. The ability to use N fixing microbes as a source of N in crops provides great benefits, including decreased N losses and increased available N later in the growing season without additional synthetic fertilizers. Pivot Bio has recently released Proven, a bacterial inoculant intended to fix N in corn. Proven is applied in-furrow at seeding and forms a mutualistic relationship with the corn, growing on its roots and consuming plant exudates while fixing atmospheric N, even in the presence of high soil N. This N fixed by Proven is then available for plant uptake. Pivot Bio claims that Proven can be used as a source of approximately 20-30 lb N/a over a growing season. The objective of this study was to determine the contribution of Proven as an N source for corn. The hypothesis was that Proven would contribute 20-30 lb N/a for corn production.

Procedures
A replicated split-plot design experiment was established at the Kansas State University Department of Agronomy North Farm in the spring of 2019. The local mean annual precipitation and potential evapotranspiration were 31.5 and 51.2 in., respectively, with a mean annual temperature of 52.52°F. The soil at the experimental site is classified as Kennebec silt loam (fine-silty, Hapludoll). The main treatment was N rate at 0, 50, 100, and 150 lb N/a applied by hand as urea immediately before planting, and the subplot factor was the presence or absence of Proven. The experiment had four replicates.
Each plot was composed of four 47-ft rows with 30-inch row spacing seeded at 28,000 plants/a.
Extensive soil sampling characterized nutrient status before, during, and after the growing season. Soil samples were collected and homogenized within each plot before planting (0-36 in), at V6 (0-12 in.), R1 (0-12), and after harvest (0-36). Inorganic soil N content was determined for each sampling by KCl extraction. Additionally, subsamples from each plot from the baseline soil sampling were tested for P, K, and pH analysis (0-12 in.). Based on these P, K, and pH results, an application of 30 lb/a of P was applied to the entire experiment in the form of triple superphosphate.
Corn growth and N uptake were documented in several ways. Stand counts were taken at R6 for the center two rows of each plot to determine the plant population in plants/a. Whole plant samples were also taken at R6 by cutting five representative plants from each of the center two rows of each plot at ground level. The plant biomass for each plot was separated from the ears and weighed separately. Subsamples of the biomass were coarse ground and dried. After drying and grinding using a 2-mm sieve, carbon and nitrogen analysis was performed. The biomass N and mass were used to calculate total biomass N content/plant, which with the stand counts was used to determine biomass N content/a.
Harvest took place when grain moisture content was less than 20%. Ears were collected by hand from each of the center two rows of a representative 10-ft area, totaling 20 ft of yield row. Ears were shelled with a stationary sheller, and the mass of the collected grain from each plot was used to estimate grain yield. A subsample of the grain was submitted to the Kansas State University Soil Testing Lab for carbon and nitrogen analysis. Grain N, along with the grain mass were used to calculate total grain N uptake/plant. The total grain N and total biomass N for each plot were summed to determine total N uptake/plant. The plant population was then multiplied by the total N uptake/plant to determine the total plant N uptake in lb/a.
Once total plant N uptake (lb/a) was determined for each plot, the amount of mineralized N (lb/a) was determined by summing the harvest soil N and total plant N and subtracting the preplant soil N. The difference in N uptake between plots with Proven and plots without Proven was calculated by subtracting the total plant N without Proven from the total N uptake with Proven. Plant N uptake with and without Proven was characterized by plotting N uptake vs. fertilizer N rate. Analysis of Variance (ANOVA) was conducted on all data using Sisvar with an alpha of 0.05 to assess the effects of N rate, Proven, and their interaction.

Results
There was no statistically significant effect of Proven (P = 0.1965) or a Proven by N rate interaction (P = 0.6209) on grain yield (Figure 1). However, increasing the rate of N fertilizer significantly increased grain yield (P = 0.0001) from 0 to 100 lb N/a with no additional increase at 150 lb N/a.
The rate of N fertilizer significantly affected total plant N uptake (P = 0.0000). The effect of Proven on total plant N uptake was not significant (P = 0.3093) nor was the interaction of Proven and N rate (P = 0.9916). However, total plant N uptake tended to be higher with Proven at all N rates (Figure 2).
Soil N mineralization without Proven produced 68 lb N/a, those treated with Proven produced 84 lb N/a, although this difference was not significant (P = 0.3358).
Although there was a tendency for a positive effect of Proven on N mineralization, it was not significant.

Preliminary Conclusions
Although there was some evidence that Proven resulted in greater N mineralization, yield, and plant N uptake, the effects were not significant. These preliminary results suggest that Proven may be acting as an N source, but the amount of N provided by Proven may not be significant, or may not be enough to produce a significant increase in yield and total plant N in the conditions present in this experiment. It is important to emphasize that these results and conclusions are based on one site and one year, so generalizations that can be made about Proven based on these results are limited.

Summary
Occasional tillage ahead of winter wheat planting could alleviate herbicide-resistant weeds, redistribute soil acidification, and improve seedbed at wheat planting. The objective of this study was to determine occasional tillage and nitrogen (N) fertilizer application effects on winter wheat, and grain sorghum yields and soil quality in a wheat-sorghum-fallow cropping system. Treatments were three tillage practices: 1) continuous no-tillage (NT); 2) continuous reduced-tillage (RT); and 3) single tillage operation every 3 years (June-July) ahead of winter wheat planting [occasional tillage (OT)]. The sub-plot treatments were assigned to four N fertilizer rates (0, 40, 80, and 120 lb/a of N). Results showed tillage had no effect on winter wheat grain yield. Averaged across the 2 study years, wheat yields were 29.4 bu/a with NT, 31.0 bu/a with RT, or 31.6 bu/a with OT. Applying N fertilizer increased wheat yield, ranging from 20 bu/a with no N fertilizer to 38.7 bu/a when N fertilizer was applied at 120 lb/a of N. However, tillage (P = 0.04) and year × N rate interaction (P = 0.003) had significant effect on grain sorghum yield. Average grain sorghum yield with RT (73.6 bu/a) was less than NT (79.4) or OT (75.4 bu/a). Averaged across tillage and years, sorghum grain yield was 60.3 bu/a with no N fertilizer and 86.8 bu/a when N was applied at 120 lb/a of N. In most years, sorghum and winter wheat grain yields obtained with 80 lb/a of N were not different from those with 120 lb/a of N, suggesting 80 lb/a of N may be adequate for both crops.

Introduction
Adoption of NT practices during fallow by many producers in the central Great Plains (CGP) has increased the quantity of residues retained on the soil surface, and soil moisture storage. This has allowed for cropping intensification in dryland systems in the CGP from winter wheat-fallow to winter wheat-summer crop-fallow or a more intensified cropping system with no fallow depending on soil water availability. The benefits of NT include reduction in soil erosion, increased soil organic matter accumulation, improved soil structure, and increased soil water storage.
Despite these benefits, stratification of soil nutrients, organic matter, and pH tend to develop near the soil surface in long-term continuous NT systems. In addition, the lack of effective herbicides for perennial grass weeds such as three-awn grass (Aristida purpurea Nutt.) and tumble windmill grass (Chloris verticillata Nutt.) control, and the emergence of glyphosate-resistant weeds pose challenges in NT crop production. In addition, in drier years, the upper layer (0-2 inches) of soils in NT tends to be "hard" and presents a challenge to placing seed in subsoil moisture at the time of wheat planting. This may cause poor plant establishment and reduce winter wheat yields. Occasional tillage of NT soils may be necessary to alleviate herbicide-resistant weed issues, redistribute soil acidity, and improve seedbed at wheat planting. The objective of this study was to determine occasional tillage and nitrogen (N) fertilizer application effects on winter wheat, and grain sorghum yields and soil quality in a wheat-sorghum-fallow cropping system.

Procedures
Field experiments were initiated in spring 2017 at the Kansas State University Agricultural Research Center near Hays, KS, to address the previously mentioned objectives. Study design is a split-split-plot with three replications in a randomized complete block design. Main plots were three crop phases of a wheat-sorghum-fallow, sub-plot treatments were three tillage practices: 1) continuous NT; 2) continuous RT; and 3) single tillage operation every 3 years (June-July) ahead of winter wheat planting (OT). The sub-sub-plots were assigned to four N fertilizer application rates (0, 40, 80, and 120 lb/a of N). The reduced tillage treatments had two to three tillage operations during fallow ahead of wheat planting and one tillage operation prior to sorghum planting. All tillage operations were done with a sweep-plow to a depth of 3 to 4 inches. Each phase of the crop rotation, tillage, and N fertilizer treatment was implemented in each year of the study. Winter wheat and sorghum grain yields were determined by harvesting a 5-× 80-ft area from the center of each plot using a small plot combine. Statistical analysis with the PROC MIXED procedure in SAS version 9.4 (SAS Inst., Cary, NC) was used to examine winter wheat and grain sorghum yields as a function of tillage and N fertilizer application.

Winter Wheat Grain Yield
Winter wheat grain yield was not affected (P = 0.54) by tillage in this study (Figure 1a). Averaged across N rates and years, wheat grain yield was 29.4 bu/a with NT, 31.6 bu/a with OT, and 31.0 bu/a with RT. Winter wheat grain yield response to N fertilizer application varied by year (Figure 1b). In 2018, there were no significant wheat yield increases when N fertilizer was applied beyond 80 lb/a of N. Nonetheless, 120 lb/a N was required for maximum wheat yield in 2019. Across years grain yield increased linearly with N fertilizer application, ranging from 20.5 bu/a with no N fertilizer to 38.7 bu/a when N fertilizer was applied at 120 lb/a of N. However, wheat grain yield was not different when N was applied at 80 lb/a of N or 120 lb/a of N in 2018 ( Figure  1b).
Tillage had a significant (P = 0.04) effect on sorghum grain yield over this 3-year study. Averaged across N rates and years, sorghum grain yields with NT (79.4 bu/a) or OT (75.4 bu/a) were not different. However, RT operations reduced sorghum grain yield compared to the other tillage treatments (Figure 2). Year × N rate interaction had a significant effect on sorghum grain yield (Figure 3). Application of N fertilizer increased sorghum yields in 2017, but grain yields produced with 40 lb/a of N were similar to those achieved with greater N rates. In the 2018 growing season, applying N fertilizer resulted in a linear increase in sorghum grain yield. Similarly, N fertilizer application did increase sorghum grain yield but significant yield increases occurred beyond 80 lb/a of N. The differences in N response between 2017, 2018, and 2019 growing seasons were because of the differences in precipitation amount in the 3 years that affected amount of available soil water for sorghum production. Across the 3 years and tillage treatments, applying N fertilizer increased grain yield from 60.3 bu/a with the check treatment (no N applied) to 86.8 bu/a with 120 lb/a of N. However, grain yield with 80 lb/a of N in 2 of the 3 years of the study were not different from that obtained with the highest N rate of 120 lb/a of N.

M.J.A. Coelho and D.A. Ruiz Diaz
Summary Phosphorus (P) fertilizer placement can affect the long-term dynamics and forms of P, and the overall soil P pools. These changes can vary by soil type, and affect P uptake and use efficiency by crops. The objective of this study was to evaluate the changes in the labile P fractions in three Kansas soil types under P fertilizer placements (broadcast versus deep band) after ten years of crop rotation. Three field studies were conducted at Scandia, Ottawa, and Manhattan. Three treatments were evaluated: 1) a control with no P fertilizer application and two fertilizer treatments (80 lb P 2 O 5 /a); 2) surface broadcast; and 3) deep band at approximately 4-6 in. depth. All treatments received strip-tillage. After ten years, soil samples were collected from the row, and between the row at two sampling depths (0-3 and 3-6 inches) and soil P pools (inorganic and organic P labile) were measured. Significant changes in soil labile P pools for treatments compared to control were observed due to the long-term effect of P fertilizer placement. The broadcast P fertilizer placement increased the total labile (Pt LP ) and inorganic labile Introduction Fixation of plant nutrients by soils is a major concern for economical use efficiency of fertilizer. Phosphorus (P) from fertilizer can become "fixed" in some soils due to conversions into compounds of limited bioavailability for plant uptake (Coelho et al., 2019;Preston et al., 2019). Phosphorus in the soil exists in inorganic (Pi) as well as organic (Po) forms of comparable solubility, and the soil fixation of all these forms depends upon many factors (organic matter content, pH, clay types, soil maximum P adsorption capacity, and fertilizer placement). Thus, efficient P management in crop production is needed to minimize depletion of soil P reserves, environmental issues due to the waste from the higher rates, and production costs. Fertilizer P placement can affect crop P utilization in the short-term during the growing season. However, the long-term interactions of placement and plant root uptake in different soils can also affect the forms of P and the overall soil P pools, especially the residual labile P concentration at various soil depths and soil-plant interactions (Adee et al., 2016). The objective of this study was to evaluate the changes in the labile P fractions in three Kansas soils under different P fertilizer placements (broadcast versus deep band) after ten years of crop rotation.

Procedures
Field experiments were conducted at the Kansas State University research and extension centers located in Scandia, Ottawa, and Manhattan. Initial soil samples were collected in April 2006 before initiating the study by collecting a representative sample from the 0-3 and 3-6 inch layers for the characterization of soil properties of the experimental areas (Table 1). A strip-tillage operation was performed before planting corn, while soybean was planted into the corn residue with no prior tillage. Strip-tillage was used for all plots, including the control, which received no P fertilizer application. Deep-band P fertilizer application was completed with the strip-tillage operation at 30-in. row spacing and made in the same row location for ten years. Corn and soybean were planted in the center of the strip in the same row each year. The phosphorus fertilizer source for the broadcast treatment was triple superphosphate (0-45-0). The P fertilizer source for deep banding was ammonium polyphosphate (10-34-0). Treatments included a control with no P application and two treatments of 80 lb of P 2 O 5 /a as a broadcast or deep band. After the last crop harvest for each experiment in 2015, soil samples were collected from 0-3 and 3-6 inches depths from the row. Soil P fractions were determined by the sequential P fractionation method (Condron et al., 1985). All statistical analyses were completed in SAS Studio (version 9.3; SAS, Institute, Inc, Cary, NC). The GLIMMIX procedure was used for the analysis of variance (ANOVA).

Results
After the ten year period, significant changes in soil P labile pools for treatments compared to the control with interaction between the two factors (treatments and soil depths) were observed due to the long-term effect of P fertilizer placement across locations.

Inorganic Phosphorus Pool
Overall, the amount Pi LP showed a higher amount in the soil surface (0-3 in.) for the broadcast treatment compared to the deep band and control treatments across locations (Figure 1 D, E, and F). However, the higher amount of Pi LP in the 3-6 in. soil layer was observed for deep band treatment. These results suggested that P fertilizer placement for broadcast in the soil surface and deep band for subsoil may contribute to the saturation of adsorption P sites in the soil under reduced tillage with minimal soil disturbance over ten years. Since the adsorption sites are gradually saturated, the binding energy of P solubilized later is weakly adsorbed and consequently increases P availability (Rheinheimer et al., 2003).

Organic Phosphorus Pool
The P fertilizer placement affected the amount of Po LP at Scandia, with no significant effects for Ottawa and Manhattan sites (Figure 1, A, B and C). The highest proportion of Po LP was observed for the control and broadcast treatments at the subsoil (3-6 in.). Also, our results showed that treatments with the largest amount of Pi LP showed the smallest amount of Po LP , broadcast in the soil surface, and deep band in the subsoil, respectively. The Pi and Po pools act in a similar way in buffering the P absorbed by plants in soils with low or no addition of P fertilizers (Coelho et al., 2019). The Po pool is considered as the main supply of P for plant uptake when no fertilizer is added to the soil, which may explain the results found in this study.

Total Labile P Pool
In general, the Pt LP showed the same tendency as Pi with higher amount in the soil surface (0-3 in.) for the broadcast and in the 3-6 in. soil layer for deep band (Figure 1, G, H, and I). In addition, preliminary results of this study suggested that the Pt LP in the soil profile (0-6 in.) showed different tendencies across locations ( Figure 2) and was affected by maximum P adsorption capacity (MPAC). The broadcast treatment showed a higher amount of Pt LP (118 ppm) than deep band (112 ppm) and control (84 ppm) treatments at Scandia site with low MPAC (288 ppm). However, at the Ottawa location with medium MPAD (348 ppm) the higher amount of Pt LP was observed for deep band (126 ppm) than broadcast (119 ppm) and control (86 ppm) treatments. In addition, at the Manhattan site with the higher MPAC (424 ppm) of this study the broadcast and deep band treatments showed the same or greater than the amount of Pt LP (174 ppm) for the control treatment (84 ppm). The maximum P adsorption capacity of these soils plus the P placement may have affected these results. With lower MPAC the continuum application of P as broadcasted in a reduced tillage may have contributed to reducing large P sorption reactions and contributed to increasing labile P concentrations near the soil surface (Coelho et al., 2019;Hansel et al., 2017). In addition, the soil with a medium amount of P fixing components, when P fertilizer is deep banded in the row with lower soil volume and minimum disturbance of the soil, can contribute to reducing the high P sorption reactions, and that may have contributed to increasing the labile P levels. However, in the soil with higher P sorption reactions the effect of P fertilizer placement as broadcast and deep band on TotP are the same in soil profile after 10 years of crop rotations, or maybe the ten years of P application were not enough to saturate the adsorption P sites of the soil.

Summary
With sulfur deficiencies being found throughout Kansas, the evaluation of sulfur fertilization and plant uptake are vital to optimize corn production. The objective of this study was to evaluate the effect of application rates of sulfur on yield and uptake in corn. Nutrient concentrations in corn biomass and grain were evaluated at the Kansas River Valley Experiment Field at Rossville, KS, in 2019. Five treatments were evaluated, including a control with no sulfur and no nitrogen (N), and four fertilizer treatments with 180 lb of nitrogen and four rates of sulfur fertilizer (0, 30, 50, and 200 lb S/a). The nitrogen source was urea and balanced for all treatments at 180 lb N/a. The sulfur-containing fertilizer applications were at the time of planting corn. Whole corn plant biomass and grain samples were taken at physiological maturity and analyzed for nitrogen and sulfur concentrations. Results for the study show that sulfur application rates have a significant yield response in corn, likely contributing to increased uptake of nitrogen. Moreover, high yielding environments increased total plant sulfur uptake and removal.

Introduction
Until recent years, sulfur is a nutrient that had often been overlooked. Increasing crop removals was due to higher yields, decreased atmospheric deposition, and a greater amount of crop residues have increased the likelihood of sulfur deficiency (Camberato and Casteel, 2017). Sulfur application is economically feasible in soils that have a severe sulfur deficiency, but not all fields respond to sulfur applications (Sawyer et al., 2011). Moreover, nitrogen application rates play a significant role in the response to sulfur application rates (Steinke et al., 2015). This study used Kansas State University's recommended rate for nitrogen for the Kansas River Valley Experiment Field and applied four different rates of sulfur.

Procedures
The Rossville field study was completed in September of 2019, initial soil samples were collected at the 0-6 in. soil layer and analyzed for various soil parameters (Table 1). The experiment was a randomized block design with four replications. Five treatments were evaluated, including a control (No N/ No S) and four rates of sulfur fertilizer (0, 30, 50, and 200 lb S/a), which will be called control, low, medium, and high, respectively. The fifth treatment solely utilized urea and served as the sulfur control treatment (Table  2). Sulfur sources include urea calcium sulfate (27% and 33%), and ammonium sulfate. The nitrogen source for the S control was urea following Kansas State University's recommended nitrogen rate (180 lb N/a). Whole plant biomass and grain samples were collected at physiological maturity in the corn crop. Whole plant biomass samples were gathered, weighed, and dried at 140°F and then reweighed to attain dry matter content. Corn was harvested, and the yield was calculated and corrected to 15.5% moisture. After corn harvest, soil samples were collected from 0-24 in. depth. All the soil samples were dried at 106°F, and sulfur was measured by a monocalcium phosphate extraction. All statistical analyses were completed in SAS (v. 9.4 (SAS Inst. Inc., Cary, NC)) using the generalized linear mixed model (GLIMMIX) procedure for analysis of variance (ANOVA).

Results
Preliminary results for this study showed significant differences between sulfur fertilization rates for both nitrogen and sulfur plant total uptake (Figures 1 and 2). Whole plant sulfur uptake significantly increased when sulfur was applied. Increasing the rate of sulfur showed no significant difference between sulfur rates (Figure 1), suggesting a rate of 30 lb was sufficient for the corn crop. Increases in nitrogen uptake were seen when sulfur was applied (Figure 2). A substantial increase in nitrogen uptake is likely linked to keeping the balance of nitrogen to sulfur within the plant. Nitrogen uptake is indicative of increased yield and sulfur uptake, suggesting that higher-yielding environments will also have elevated levels of sulfur removal (Figure 3). Soil sulfate levels in the 0-24 in. soil profile post-harvest were only significantly different at the high sulfur rate (Figure 4). This is likely due to excess S applied related to corn total need. Preliminary results show that the highest sulfur application rate significantly increased yield compared to the urea-only application ( Figure 5). This suggests sulfur applied at the lowest rate may have not been sufficient for maximum yield. An increase in nitrogen provided significantly more yield gain over the control when compared to sulfur.      Figure 5. Corn yield response as affected by different rates of sulfur application. Letters represent significant differences between treatments at P < 0.05.

Introduction
The availability of phosphorus (P) and potassium (K) is typically assessed with a soil test and a calibration curve relating test values to relative yield or nutrient uptake. Several soil tests for P and K have been introduced over the years. Historically, Bray-1 and Olsen have been the dominant soil test methods used for P analysis in the Central Plains region, while ammonium acetate has been used for base cations (e.g. K, Ca, Mg, Na). Usage of Bray-1 vs. Olsen is largely dependent on soil pH, where Bray-1 is preferred in acidic soils and Olsen in calcareous soils. The Mehlich-3 (M3) procedure has gained popularity in recent years, and is intended for use in acidic to neutral pH soils. It has been dubbed a "universal" extractant by some, due to its ability to extract multiple nutrients across a wide range of soil pH. When combined with modern spectroscopic techniques (e.g. ICP-OES), this procedure allows for the simultaneous measurement of multiple macro and micronutrients from a single extract. This has led to wide adoption of the M3 soil test procedure at labs across the US.
The Haney H3A extracting solution is intended to simulate the chemistry of actively growing roots more closely (Haney et al., 2006). The H3A extracting solution is comprised of a dilute mixture of organic acids, but has undergone numerous iterations since its initial development (Haney et al., 2017). The current iteration, version 4, is comprised of malic, citric, and oxalic acids, and has a weakly buffered pH of approximately 3.75 (Haney et al., 2017). The primary objectives of this study were to investigate relationships between M3 and H3A soil test P and K in selected Kansas soils.

Procedures
Field studies were initiated at multiple sites across the state of Kansas during the 2017, 2018, and 2019 corn growing seasons, 14 site-years in total (Table 1). Treatments consisted of nitrogen (N), P, and K fertilizer combinations applied at rates ranging from 0 to 200 lb N/a, 0 or 80 lb P 2 O 5 /a, and 0 or 100 lb K 2 O/a. Soil samples were collected from each plot using a hand probe to a depth of six inches prior to treatment application. Soil measurements include soil pH, OM, M3 and H3A-4 extractable P, K, Ca, Mg, Al, Cu, Fe, Mn, and Zn.
Relationships between Mehlich-3 and H3A-4 extractable nutrients were evaluated using linear regression models. Data analyses were performed in R version 3.6 (R Core Team, 2019) and evaluated at the 95% confidence level.

Results
Mehlich-3 and H3A extractable P and K were highly correlated (r = 0.90 and 0.91, respectively) and exhibit a linear relationship in combined data (Figures 1, 2). On average, M3 extracted approximately 25% more P and 250% more K than H3A-4 ( Figures  1, 2). The RMSE of these regression models (15.4 mg P kg soil -1 and 83.4 mg K kg soil -1 ) is too large to allow for estimation of M3 P or K from H3A-4 P or K for the purposes of fertility recommendations. Existing calibration curves for soil test P and K for Kansas soils are based on either Mehlich-3 or Bray-1. These data clearly illustrate that separate calibrations would be required to make fertilizer recommendations from H3A-4 P or K soil tests.

Introduction
Some soil test methods used to estimate K availability (e.g. 1 M NH 4 OAc) are not always good indicators of K uptake by plants. Since the 1950s, synthetic ion exchange resins have been used for assessing the bioavailable fraction of soil nutrients (Qian and Schoenau, 2002). Compared to soil test methods, ion exchange resins can be used to measure nutrient supply rates during specific adsorption periods. Therefore, soil processes, such as nutrient release and transport, can be considered. In CER, membranes are negatively charged in order to adsorb positively-charged ions, like K + . Exchange membranes were adequate to assess immediate nutrient supply rate by selecting short burial periods (1 hour) (Qian et al., 1996). Also, long periods are used to capture nutrients released from mineral and non-exchangeable forms (Cooperband and Logan, 1994). This technology has potential applications in numerous areas (including agronomic research) because of its ability to simulate plant root activity in undisturbed conditions. However, there are still limitations such as the unfamiliarity of units used to express results (Qian and Schoenau, 2002), and lack of calibration studies related to crop response. Commonly, K management is based on pre-plant soil sampling to assess nutrient supply for the entire season. Finding an indicator that considers the kinetics of K release from the soil could be useful to improve future management. The objective of this study was to evaluate whether K adsorbed by CER could be used as an indicator of in-season K supply to soybean in field conditions.

Procedures
Field experiments were conducted at two locations in eastern Kansas during 2019 (Table 1). Sites were located at Ashland Bottoms (Manhattan, KS) and Ottawa, KS, under a conventional tillage system. Treatments included a control (check) with no K application and one with an application of 150 lb K 2 O/a (high K rate). Both treatments had an application of 80 lb P 2 O 5 /a. The fertilizer applications were a surface broadcast at pre-plant using triple superphosphate (TSP) and potassium chloride (KCl) as a P and K sources, respectively. For this study, we used a commercial CER PRS as an indicator of the in-season K supply to soybean. This product consists of an exchange resin membrane held in a plastic frame that is inserted into the soil to measure in situ ion supply. The Ottawa location had six burial periods and Ashland had seven. Burial length consisted of 7 days with a time between burials of 15 days. A total of 4 probes were distributed within the plot to obtain a composite sample. The CERs were inserted vertically into the soil (facing plant row), between 2-4 inches soil depth at a distance of 3 inches from the soybean row. For every new burial period, the CERs were buried 5 inches apart from the previous period (parallel to the row) to avoid sampling the same portion of soil. Aboveground plant samples were collected at V4, R2, R4, and R6 stages in order to measure plant K uptake. Soil samples were taken at the beginning and end of each burial period to calculate soil moisture content (air-dried at 104°F). Statistical analysis (ANOVA) was performed using the GLIMMIX procedure in SAS v. 9.4 (Cary Inst. Inc., Cary, NC).

Results
Plant K uptake measured at reproductive stages (R2, R4, and R6) was increased by K fertilization in both locations (Figure 1). Location 2 had significantly higher plant K uptake measured at R2, R4, and R6 stages when 150 lb K 2 O/a was applied (Figure 2). At the R6 stage, fertilized plots had 50% more K uptake and 40% more K adsorption (cumulative) by CER compared to the control. This observation suggests the potential use of CER as an indicator of K supply to soybean in field conditions. In both locations, CER were able to adsorb more K (measured as cumulative adsorption) at high K rate. The amount of K that was adsorbed by the CER was influenced by soil moisture content, particularly at location 1 (Figure 3). A similar trend was observed between these two variables. Plots without K fertilization were less affected, and minor fluctuations were measured compared to those with high K rate. However, data from location 2 did not show a clear pattern (Figure 4). Preliminary results from this study suggest that CER can be used as an indicator of K supply, particularly in low K soils.

Introduction
In general, winter wheat is one of the most responsive crops to P fertilizers in Kansas, making starter P fertilizer common across the state (Ruiz Diaz and Weber, 2019). Some producers lack fertilizer setups on their drills and commonly blend dry P fertilizers with wheat seed and then drill both together in the same hopper to get a starter fertilizer effect. However, little research has been done to address concerns with potential injury to wheat seed when mixed with different phosphorus fertilizer rates and timings. Thus, increases in nitrogen fertilizer rates (salt) in the seed furrow commonly cause issues with seed germination and the fall stand of wheat. This could ultimately decrease fall stands of the crop, which leads to a greater need for fall/spring tillering to recover this reduction in fall stand. In addition, the following questions arise "How long can dry fertilizer sit with the wheat seed?" and "Will it cause the same damage as a high starter fertilizer rate in-furrow?" This report provides a summary of results from an ongoing study evaluating the effect of fertilizer rates and fertilizer time exposure to wheat seed, and effects on wheat grain yield.

Procedures
The study was conducted at two locations during the 2018-2019 wheat growing season at Manhattan (site 1) and Topeka (site 2) in northeast Kansas near Kansas State University (Table 1). The previous crop for site 1 was soybean and site 2 was corn. The winter wheat variety Everest was mixed with DAP (18-46-0) and Micro-Essentials SZ -MESZ (12-40-0-10S-1Zn) fertilizers. The blend of seed and fertilizer was stored in open plastic buckets for 0, 12, 28, and 40 days before drilling. Rates included 0, 30, 60, and 120 lb P 2 O 5 /a with 70 lb wheat seed/a (a complete combination of P rates and times for two P fertilizer sources). No nitrogen (N) was applied in the fall except for the N present in DAP and MESZ fertilizers. At green-up, 100 lb N/a was applied to all plots to ensure N was not a limiting factor. Normalized difference vegetation index (NDVI) measurements were taken at jointing (Feekes 6) stage with a Holland RapidSCAN CS-45 active sensor ran 35-40 inches above the crop canopy. Averages of NDVI readings were then recorded for each treatment. Biomass samples were collected at jointing (Feekes 6) and were taken from 2.5 feet of row times two rows in the backside of the plots. Additional biomass samples were taken at soft dough (Feekes 11.2) in the same manner as the jointing biomass samples. Grain harvest was completed with a plot combine, and subsamples were taken from each treatment. All biomass samples and grain were analyzed for P concentrations using the salicylic-sulfuric acid digestion method (Miller and Keeney, 1982). All statistical analyses were completed using SAS Studio (version 9.4; SAS, Institute, Inc, Cary, NC). Analysis of variance (ANOVA) using the GLIMMIX procedure was conducted.

Early Growth
Increases were observed in NDVI when increasing rates of P 2 O 5 were mixed with the seed with both DAP and MESZ fertilizer sources ( Figure 1A). However, no significant differences were observed when DAP was mixed while increasing time intervals. When MESZ was mixed, the NDVI values at jointing were lower for the longer time interval of 40 days ( Figure 1B). Also, significant increases were observed in total P uptake at jointing when using increased rates of both P fertilizer sources ( Figure 1B). However, there were no significant effects of time mixed and total P uptake at jointing with either P fertilizer sources ( Figure 1D).

Grain Yield and Phosphorus Removal
Preliminary results of this study showed that as rates of both P fertilizer sources were increased, significant increases were observed in the total amount of P removed in wheat grain ( Figure 2A). However, when looking at the duration of the source mixed with seed, no significant results were found for DAP, but a slight decrease was observed in P removal for the longest MESZ mixing time of 40 days ( Figure 2B). In addition, the yield was significantly increased as rate of both P fertilizer sources increased ( Figure 3B). Also, the time DAP was mixed with seed had no significant effect on grain yield, while the longest mixing time using MESZ resulted in a small decrease in wheat grain yield ( Figure 4B).
Based on these preliminary results, P rates in-furrow were the primary driver for increasing NDVI at jointing, P uptake at jointing, grain yield, and P removal with the grain. This response was significant up to the highest P rate for both fertilizer sources and likely due to the combination of low soil test and late planting date for the wheat (due to unfavorable weather conditions). The time DAP was mixed with wheat seed had no effect on any of the measurements taken which indicates producers have flexibility regarding the time elapsed between mixing the seed and fertilizer, and planting. In this study, the storage conditions were in a dry environment to prevent fertilizer from absorbing water; it is possible that conditions of high relative humidity might affect the physical characteristics of the seed-fertilizer blend. The overall trends observed in these preliminary results suggest that either P fertilizer source can be stored for a prolonged period of time with no negative impact, and producers can avoid the economic expenses of replacing the seed-fertilizer blend.   Figure 1. Normalized difference vegetation index (NDVI) measurements taken at the jointing (Feekes 6) stage with comparison made between fertilizer source rates mixed with seed (A), and comparison made between fertilizer mixing duration with seed (B). Phosphorus (P) uptake, lb/a, at the jointing (Feekes 6) stage with comparison made between fertilizer source rates mixed with seed (C), and comparison made between fertilizers mixing duration with seed (D). DAP = diammonium phosphate. MESZ = Micro essentials fertilizer. . Phosphorus (P) removed in grain lb/a at grain harvest with comparison made between fertilizer source rates mixed with seed (A) and comparison made between fertilizer mixing duration with seed (B). Grain yield in bu/a with comparison made between fertilizer source rates mixed with seed (C), and comparison made between fertilizers mixing duration with seed (D). DAP = diammonium phosphate. MESZ = Micro essentials fertilizer.