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Fluid Journal : Early Spring 2012
09 The Fluid Journal Early Spring 2012 with treatments that contained very little N at planting and 2 gal/A of ATS (treatment 2 and 8). Total N uptake was 10-12 lbs/A less with treatments 11 and 12 even though they had greater early growth (V7 dry matter yield) and greater RLC. Treatments 11 and 12 contained the greatest amount of N (31 and 34 lbs/A, respectively) at planting in combination with P and S. These data show less total N was taken up by corn when more N was applied at planting and less N was applied at V2. This suggests greater N loss occurred during the wet period in June and July on treatments that received more N at planting. A reduction in N uptake probably reduced yield potential in these treatments during a high N stress growing season in 2010. Stover and total uptake of K was greatest with the 4 gal/A rate of ATS compared with 0 or 2 gal/A rates, when averaged across APP and UAN treatments. Generally, stover, grain, and total S uptake increased with increasing rate of ATS. Total S uptake in the corn plant increased only 2.1 lbs/A for the 4 gal/A rate of ATS (11.5 lbs S/A) compared with the control when averaged across APP and UAN treatments. Interactions. Several significant (P<=0.10) interactions were found for stover, grain, and total nutrient uptake. An APPxUAN interaction for stover K showed K uptake was reduced about 11 lbs/A when UAN was applied without APP, while other combinations of APP and UAN (with UAN and with APP, no UAN and no APP, and no UAN with APP) had similar K uptake (data not shown). The significant UANxATS interactions for grain N, P, and S uptake and total P uptake were similar to and a result of the same interaction for yield (Figure 2). Moreover, greatest nutrient uptake values were obtained with 2 or 4 gal/A of ATS without UAN. When UAN was applied, uptake values across all rates of ATS were similar (data not shown). The APPxUAN interactions for grain P and K uptake were similar and showed P and K uptake was greatest when either APP or UAN was applied, while uptake was reduced when both were applied (data not shown). An APPxATS interaction for total P uptake showed, when APP was not applied, P uptake was 37, 39, and 41 lbs/A for the 0, 2, and 4 gal/A rates of ATS, respectively. However, when APP was applied, P uptake was 40, 39, and 38 for the 0, 2, and 4 gal/A rate, respectively (data not shown). Generally, these small differences in nutrient uptake from one- site year of data would not raise much concern. However, these data suggest a potential for negative consequences when combinations of fluid fertilizers are applied at planting. Whether that potential is realized will depend on the interactions expressed in years 2 and 3 of this study. Consistent and repeated responses would lead to more definitive conclusions. The significant three-way interaction for K uptake in grain has no plausible explanation. Rochester site Plant height. Plant heights and dry matter yields were increased with 4 gal/A of APP applied in-furrow compared with 0 gal/A when averaged across UAN and ATS treatments. Plant heights and dry matter yields were not affected by the main effects of UAN and ATS application and there were no significant interactions. This suggests that the early growth response at this site was primarily due to P in the APP starter. Adding 1 gal/A of ATS to 4 gal/A of APP in-furrow had no effect on plant height and dry matter yield compared with APP alone. Nutrient concentration. Nitrogen and S concentrations in V7-8 corn plants were reduced with APP application, averaged across UAN and ATS treatments. This response is likely a result of the "dilution effect." The dilution effect occurs when early growth increases dramatically, thus causing concentrations of some nutrients to decline. The large increase in dry matter yield with APP fertilization observed in this study resulted in increased NPK and S uptake compared with plots that did not get APP. When UAN was applied at planting, P concentration in small plants decreased slightly, while S concentration and uptake increased. Four gal/A of ATS increased N concentration in small plants compared to the 0 and 2 gal/A treatments, when averaged across APP and UAN treatments. Sulfur concentration increased as ATS rate increased, but no differences in S uptake were found. Adding 1 gal/A of ATS to 4 gal/A of APP in-furrow generally did not affect nutrient concentrations or uptakes in small corn plants compared with APP alone. The highly significant APPxATS interactions for K concentration and uptake in V7-8 corn plants showed that without APP, K concentration and uptake declined when ATS was applied. Whereas with APP, K concentration and uptake increased as the rate of ATS increased (data not shown). Lowest K concentrations and uptakes were found when APP was not applied and 4 gal/A of ATS was applied (data not shown). These results were not found at the S-responding Waseca site. The three other interactions had P values slightly less that alpha = 0.10 level of significance. However, the author feels they are of little consequence and do not warrant further discussion. Grain moisture. Grain moisture was reduced 0.9 percentage points with 4 gal/A of APP compared with 0 gal/A when averaged across UAN and ATS treatments. Application of UAN reduced grain moisture slightly (0.3 percentage points), when averaged across APP and ATS treatments. Three significant interactions (APPxATS, UANxATS, and APPxUANxATS) were found for corn grain moisture. Generally, these interactions showed that when APP was not applied, grain moisture was reduced with ATS with or without UAN. However, when APP was applied, grain moisture response to ATS with or without UAN was erratic. Yields. Corn yields only ranged from 207 to 213 bu/A across all 14 treatments in this study. No significant differences were found among treatments and there were no interactions. No differences in final plant population were found among treatment main effects. RLC. At VT-R1, relative leaf chlorophyll ranged from 94.6 to 99.1 percent and was not affected by the main effects of APP and UAN application. The 2 and 4 gal/A rates of ATS increased RLC about one percentage point compared with the 0 gal/A rate of ATS when averaged across APP and UAN main effects. The author has no plausible explanation for the significant three-way interaction for RLC. Vetsch is Soil Scientist at the Southern Research and Outreach Center at the University of Minnesota.
Late Spring 2012