Closing Corn Yield Gaps via Improved Management: A Systems Approach

Three corn research trials were conducted during the 2016 growing season. Two studies were conducted at Scandia, KS, (dryland and irrigated) and one at Topeka, KS (dryland). The objective of these trials was to investigate the contribution of different farming systems for closing corn yield gaps. Each experiment consisted of five treatments: common practices (CP), comprehensive fertilization (CF), production intensity (PI), ecological intensification (CF + PI), and advanced plus (AD). Across all three experiments and under dryland and irrigation scenarios, CP presented the lowest yield. In environments with yield response, intensifying production without a balanced nutrition program did not increase yields. A balanced nutrition program substantially increased yields in corn with more relative impact in dryland environments. The absolute yield gap was 86 bu/a for dryland and 75 bu/a for irrigated condition.


Introduction
Crop management practices (such as row spacing, planting date, and nutrient application) and their interactions with the environment (soil + weather) have a direct impact on closing yield gaps. By choosing different combinations of practices, farmers can modify the growing conditions. Thus, after considering the contribution from the genetics and the environment, on-farm yield is primarily influenced by farmers' decisions, the main components of which are agronomic practices. Crop management practices are often specific to the environment, hybrid/variety, and/or yield level. Each farmer needs to find the appropriate management practices that can help them increase yields and profits. Increasing seeding rates and narrowing rows are two common intensification practices in high-yielding corn systems.

Procedures
Three corn research trials were conducted during the 2016 growing season. Two studies were located at the North Central Kansas (NCK) experiment fields (Scandia, KS), and one at the Kansas River Valley (KRV) experimental fields (Topeka, KS). At Scandia, one experiment was conducted under dryland and one under irrigated conditions. The corn was planted on May 6 at both locations. Each experiment consists of 5 treatments with five replications in a completely randomized block design: 1) common practices (CP), (30,000 seeds/a + no-nutrient application + 30-in. row spacing); 2) comprehensive fertilization (CF), (30,000 seeds/a + balanced nutrient application + 30-in. row spacing); 3) production intensity (PI), (36,000 seeds/a + no-nutrient application + 15-in. row spacing); 4) ecological intensification (CF + PI; 36,000 seeds/a + balanced nutrient application + 15-in. row spacing + fungicides and micronutrients); and 5) advanced plus (AD), or increasing input applications (36,000 seeds/a + balanced nutrient application + 15-in. row spacing + double application of fungicides and micronutrients). Mes SZ and Aspire (Mosaic company) rates in lb N-P 2 O 5 -K 2 O-S/a for irrigated were 141 and 133 lb/a, while for dryland fertilizer P and K rates were 105 and 99 lb/a, respectively. Nitrogen rate for the treatments of CF, ecological intensification (EI ) (CF+PI), and AD was 175 lb/a of UAN (28%). The EI and AD treatments received an extra 175 lb/a of UAN at flowering. The rates per nutrients in lb/A (N-P 2 O 5 -K 2 O-S-Zn-B) were 73-56-80-14-1.4Zn-0.65B and 68-42-105-11-1Zn-0.85B for irrigated and dryland scenario.

Weather Conditions
Weather conditions for the growing season and historical values are shown in Figure 1 for the NCK site and Figure 2 for the KRV location (Mesonet, Kansas State University). The total amount of precipitation received during the growing season was 17 inches at both locations.
The total amount of water provided to the irrigated condition at NCK site was 6.3 inches (6/23, 7/15, 7/21, 7/29, and 8/10). Temperatures ranged in normal values for the crop, registering only a few days of heat stress.

Soil Test and Phenological Information
Soil samples were collected before planting to characterize each experimental site. Soil test results are shown in Table 1. The previous crop was soybean at all locations. The corn hybrid planted, the date for phenological stages, and the harvest date are shown in Table 2.

North Central Kansas, Scandia, Yields
At the NCK Scandia field experiment, average yield for dryland corn was 159 bu/a; while irrigation yielded on average 190 bu/a (+19%). In both water scenarios there were statistical differences (P < 0.05) between treatments, CP and PI recorded the lowest corn yields, and CF the highest values, 199 bu/a for dryland and 226 bu/a for irrigated (Figure 3). Common practices (CP) and intensification without balanced nutrition (PI) treatments obtained the lowest yields under both water scenarios (CP vs. PI, 113 < 122 bu/a for dryland and 164 > 151 bu/a for irrigated). Intensifying management practices with balanced nutrition (EI) treatment yielded more than CP and PI but less than CF (Figure 3). The absolute yield gap was 86 bu/a for dryland and 75 bu/a for irrigated condition (calculated as the maximum yield value, CF treatment, minus lowest yield value, CP treatment for dryland, and PI for irrigation) (Figure 3).

Kansas River Valley, Topeka, Yields
At the KRV Topeka field experiment, average corn yield was 156 bu/a ranging from 150 to 163 bu/a (Figure 4). There were no statistically significant differences between all the treatments (P > 0.05) evaluated in this location during the 2016 growing season.