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Fluid Journal : Fall 2017
9 The Fluid Journal Fall 2017 Table 8. Impact of side dress and top dress K on grain yield for Byron, IL 2016. Treatment 123 Grain Yield (bu ac-1) Mean Stdev Check 225.3 11.8 50 Kac – Spoke Wheel 222.7 7.8 100 Kac – Spoke Wheel 220.1 14.7 100 K2SO4 Top Dress 242.5* 13.7 1 Soil Test K levels by site: 132 ppm, respectively. 2 Fertilizer application: top dress dry pre-emergence over row; spoke wheel side dressed V3-V4 rates lbs ac-1. 3 Column means followed by (*) are significant at the 0.05 level from the check treatment (7 reps). Figure 3. Diagram of theorized optimum maize ear leaf nutrient ratios based on Elwali et al (1985). site (Table 2). Only the VN treatment showed significant increased grain yield for the 32K and 38K populations. There was no increase in grain yield over the check treatments with K or in combination with N. For the Sutherland, IA site it was noted that there was limited rainfall (<0.25 inches) for two weeks after the sidedress fertilizer treatment, which may have impacted crop uptake. Sidedress N and K fertilizer applications at growth stage V3 to V4 at the Dodgeville, WI site had no statistically significant impact on grain yield within each of the four populations (Table 3). The same was true for the Farmer City, IL site (Table 4). It is worth noting that there was a strong trend showing N and K increasing yield for the 44K population, however it was masked by herbicide damage and subsequent variability. For the Wellington, CO site in 2015, sidedress N (50N) and NK (50N + 50K) fertilizer was applied at growth stage (GS) V4 to V5 (Table 5). The application of 50 N alone increased grain yields only for the 48K population treatment. The application of 50N + 50K significantly increased yield statistically across all populations and for the 48K population resulted in a grain yield increase of 77.9 bu ac-1 over the check plot. The Linden, WI, the population study site in 2016 showed large increases in grain yield N and N+K over the check treatments for all three populations, with an average yield increase of 28 bu ac-1 sidedress N, and36buac-1toN+Kacrossall populations (Table 6). This site had a lower STK (154 ppm) and had ideal temperature and moisture conditions during corn CS V2-R1. K source study. N and K source studies were conducted at three Midwestern sites in 2015 and one site in 2016. Results for 2015 show grain yield responses to N alone at two sites and to K alone at one site (Table 7). Fertilizer treatments of N Table 6. Impact of population and side dress N and K source on grain yield for Linden, WI 2016. Treatment 123 Grain yield (bu ac-1) Plants ac-1 x 1000 32k 38k 44k Check 220.1 Delta Yield 234.6 Delta Yield 216.4 Delta Yield 50N 240.8 20.7 * 266.7 32.1 * 247.2 30.8 * 50N+50Kac 256.1 36.3 * 274.6 40.0 * 261.4 45.0 * 1 Soil test K level 156 ppm. 2 Fertilizer sources: Nitrogen urea; K acetate, rates lbs ac-1 . 3 Mean results followed by (*) are significant at the 0.05 level from the check treatment. Table 7. Impact of side dress N and K Source on corn grain yield for three Midwest sites 2015. Treatment 123 Grain Yield (bu ac-1) Calumet, IA Linden, WI Weedman, IL Check 194.1 219.0 183.2 50N 217.1 * 229.6 200.2 * 50 Kac 205.9 230.6 * 187.4 50N+50Kac 212.1 * 239.2 * 195.4 * 50N+50KKCl 204.1 240.5 * 203.8 * 1 Soil Test K levels by site: 192, 178 and 184 ppm, respectively. 2 Fertilizer sources: nitrogen urea; K acetate and KCl, rates lbs ac-1 . 3 Results followed by (*) are significant at the 0.10 level from the check treatment. Table 9. Cluster comparisons of corn GS R1 ear leaf N, K, K:Mg, N:Mg and yield 2016. Parameter Low Leaf K Cluster 123 High Leaf K Cluster Mean Stdev Mean Stdev N% 2.51 0.26 2.83 0.18 K% 1.50* 0.22 2.76 0.35 Mg% 0.41* 0.05 0.17 0.04 N:K 1.71* 0.21 1.05 0.15 K:Mg 3.6* 0.7 17.1 3.8 N:Mg 6.0* 0.9 17.7 3.5 Yield (bu ac-1) 196.1 37.2 241.7 23.1 1 Ear leaf K, Mg and yield measurements based for 32 sites, 4 reps per site, across five states. 2 Cluster analysis comparison of eight lowest and highest ear leaf K. 3 Cluster means within a parameter followed by (*) are significant at the 0.05 level. “Further research needed to develop predictive models.”