Successful N management practices for the US Midwest must optimize crop production and minimize NO3-N losses from subsurface tile drainage. The objective of this study was to measure the effects of N rate, N application timing, and nitrapyrin [2-chloro-6-(trichlormethyl) pyridine] on corn (Zea mays L.) production and NO3-N in tile drainage water in a corn-soybean [Glycine max (L.) Merr.] rotation in Minnesota. Anhydrous ammonia was applied at 90 and 179 kg ha−1 with nitrapyrin in the fall and at 134 kg ha−1 with and without nitrapyrin in fall and spring. However, drainage water monitoring was only conducted on fall treatments. Over a 5-yr period, 71% of drainage occurred in April through June and <1% occurred from November through March due to frozen soil. Averaged across N treatments and crops, annual drainage ranged from 69 to 380 mm among years. From 2001 through 2003, NO3-N concentrations averaged 13.8, 15.6, and 20.0 mg L−1 in corn and 7.3, 8.2, and 12.6 mg L−1 in soybean when 90, 134, and 179 kg N ha−1 was fall applied with nitrapyrin to corn, respectively. Corn grain yields were greater with spring-applied N at 134 kg ha−1 (11.3 Mg ha−1) than with fall-applied N at 134 and 179 kg ha−1 with nitrapyrin (10.5 and 10.8 Mg ha−1, respectively), and nitrapyrin did not affect corn production or water quality. Fall application of N is common on cold soils in Minnesota. These data showed that fall application required a greater rate of N to optimize yield than spring and that greater fall rate often increased NO3-N concentration and load in tile drainage water.
Bibliographical noteFunding Information:
J.A. Vetsch and G.W. Randall, Southern Research and Outreach Center, Univ. of Minnesota, 35838 120th St., Waseca, MN 56093; F.G. Fernández, Dep. of Soil, Water and Climate, Univ. of Minnesota, 439 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108. This research was supported in part by Dow AgroSciences. Assigned to Associate Editor Aaron Glenn.
The authors thank David Groh and Warren Rugger for collection of the data. Partial funding of this research was provided by Dow AgroSciences and is greatly appreciated.
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