Organization: University of Minnesota, Southern Research and Outreach Center
Despite considerable acres being converted to corn-corn-soybean (C-C-S) rotations in Minnesota, most of the nitrogen management information available is specific to corn-soybean rotation. Since the effects of nitrogen rate and application timing on nitrate loss in tile drainage are not known under high-yield conditions, this study set out to answer the following questions:
What is the effect of nitrogen (N) rates and timing of application on corn production, profitability and nitrate losses to drainage water in a C-C-S rotation?
What happens during the second year of corn?
What is the effect of a slightly reduced N rate when split-applied (preplant + sidedress) versus a “full” rate of spring preplant N on corn production, profitability and nitrate losses to drainage water?
What is the level of nitrate losses from first-year corn, second-year corn and soybeans in a C-C-S rotation if N is not applied to corn?
Will recommended N rates be sufficient for maximum profitability in the long run if 200+ bushel-per-acre yields continue?
Applying a slightly reduced N rate (85% of recommended) split between preplant urea and V3 injected at the urea ammonium nitrate (UAN) growth stage did not perform well in first-year corn, and thus would not be recommended. However, for second-year corn, split application performed well with increased yield, N uptake, and economic return to N, in addition to less nitrate loss to tile drainage water.
Based on the data for the C-C-S system, split-applying 85% of recommended N rate resulted in about 10% less nitrate loss to drainage water than from the 100% preplant rate in this C-C-S rotation.
Nitrate losses from the C-C-S rotation were calculated to be at least 14% greater than from a C-S rotation.