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Fluid Journal : Fall 2013
8 The Fluid Journal Fall 2013 Whole plant dry matter yields were increased 21, 42, and 12 to 18 percent by the main effects of APP, UAN, and ATS applications, respectively. Greatest dry matter yields were obtained when all three starter fertilizers were applied (treatments numbers 11 and 12). Dry matter yields of V6 corn plants that received a starter containing APP, UAN, and ATS were nearly double the yield of the control treatment. The application of fluid fertilizers at planting resulted in dramatic visual differences (greater early growth and plant uniformity and a darker green color) in May and June of 2012. Nutrient uptake. Generally, all starter treatments (APP, UAN and ATS) increased nutrient uptake of V6 corn plants at Waseca (Table 2). Nitrogen uptake increased about 15 percent when APP was applied in-furrow and about 45 percent when UAN was applied as a surface band. Moreover, P uptake increased about 19 percent when APP was applied in-furrow and about 31 percent when UAN was applied as a surface band. Numerically, the greatest N, P and S uptakes occurred when all fluid starters (APP, UAN and ATS) were applied (treatment numbers 11 and 12). These data show how fluid starter fertilizer application can dramatically increase early growth and nutrient uptake of corn. Grain moisture & yield. Treatment effects on grain moisture, grain yield, initial plant stand and final plant population are presented in Table 2. The summer drought resulted in grain that was very dry at harvest, especially considering the early harvest date (September 19). Grain moisture was reduced about 0.5 percentage points by the main effects of APP and UAN application at planting. Corn grain yields ranged from 205 to 216 bu/A. However, grain yields were not affected by APP, UAN, and ATS application at planting. The dramatic differences in early growth that occurred early in the growing season did not result in increased yields in this warm and dry growing season. Initial plant stand and final plant population (after thinning) were not affected by any of the treatments at this location in 2012. Rochester results Weather. The 2012 growing season, similar to Waseca, was considerably warmer than normal. Unlike Waseca, Rochester received significantly greater rainfall in July and August, which resulted in excellent crop growth and development (Table 1). Growing season precipitation totaled only 2.47 inches less than normal for the period May through September. Early growth of corn as measured by V6 plant heights and whole plant dry matter yields was affected by two of the main effects in the factorial analysis of treatments (Table 3). When averaged across APP and ATS main effects, heights and yields of V6 corn plants were increased slightly with UAN application. Dry matter yields were only 13 percent greater with APP application when averaged across UAN and ATS rates. Moreover, these data showed early growth of corn at the Rochester location, a well drained silt loam soil, was less responsive to starter fertilizers compared with the Waseca location, a poorly drained clay loam soil. Plant height CV was not affected by the main effects at Rochester. However, a significant APP×UAN interaction (interaction statistics not shown) for CV showed CV was numerically greatest (heights were more variable) when APP and UAN were not applied. Nutrient uptake. Nitrogen, P, and S uptakes increased about 15 percent with APP applied in-furrow, when averaged across UAN and ATS main effects (Table 3). Nitrogen uptake increased only 11 percent when UAN was applied as a surface band. Increases in nutrient uptake were primarily a result of small increases in dry matter yield as concentrations were not affected by treatments (concentration data not shown). These data are contrary to what was observed at Waseca and result from smaller differences in dry matter yield at Rochester. Grain moisture & yield. Treatment effects on grain moisture, grain yield, initial plant stand and final plant population are presented in Table 3. Corn grain was very dry at harvest. It ranged from 15.9 to 17.3 percent among treatments. A significant APP×UAN interaction (interaction statistics not shown) for grain moisture showed moisture was greatest when APP and UAN were not applied and less when either or both were applied. Corn grain yield decreased 6 bu/A with 4 gal/A of APP compared with 0 gal/A of APP, when averaged across UAN and ATS treatments. Initial plant stand was reduced 500 to 600 plants/A with UAN and APP application and after thinning final plant populations were slightly (300 plants/A) less with UAN application. It is unlikely that small final plant population differences reduced yields at this location. However, the combination of initial stand and grain yield reductions with APP suggests some negative effect of in-furrow placement on this silt loam soil. Non-uniform rainfall distribution early in the growing season may have contributed to these responses. About 3.5 inches of precipitation fell in the 14-day period after planting, while the next 18 days brought only 0.1 inches. Then 3.3 inches of precipitation were recorded in 3 days, followed by a 19-day period with only 0.5 inches. It's possible the 6 bu/A yield reduction with APP and the plant stand reduction with APP and UAN application could be a result of salt injury during these extended dry periods. Plant stand. Significant UAN×ATS and APP×UAN×ATS interactions (interaction statistics not shown) for plant stand showed stand was reduced about 1,000 plants/A when two (UAN and ATS) or all three starter fertilizers were applied at planting. These data suggest the distance from the row to the location of the surface dribble band should be greater than the 2-inch distance used in this study. Summing up A record warm spring produced rapid early growth and development of corn in 2012. A summer drought resulted in increased yield variability at Waseca. Early growth responses to starter fertilizer treatment varied between locations, while yield responses were similar. At Waseca, early growth and plant-to-plant uniformity of corn were greatly enhanced with fluid starter fertilizers but grain yields were not affected, whereas at Rochester early growth responses were smaller, less frequent, and positive yield responses were not observed. Mr. Vetsch is an Assistant Scientist and Dr. Randall is Professor Emeritus at the Southern Research and Outreach Center, University of Minnesota, in Waseca, MN, and Dr. Kaiser is an Extension Nutrient Management Specialist and Assistant Professor in the Department of Soil, Water, and Climate at the University of Minnesota, Twin Cities. "Crop response to treatments varied."
Late Spring 2013