Rasse, D. P., J. T. Ritchie, W. R. Peterson, J. Wei, and A. J. Smucker. 2000. Rye cover crop and nitrogen fertilization effects on nitrate leaching in inbred maize fields. Journal of Environmental Quality 29:298-304.
Nitrate leaching from maize (Zea mays L.) fields fertilized in excess of plant requirements continue to threaten water quality even though many agronomists have recommended reducing N fertilization rates to contain this environmental risk. Inbred maize has lower N uptake than conventional hybrid maize; therefore, inbred maize production exposes soils to even greater ground water pollution risks by nitrates. A 3-yr field experiment was conducted on sandy loam soils in southwestern Michigan to investigate the combined effects of N fertilization rates and rye (Secale cereale L.) cover crops on NO3 leaching in inbred maize fields. Inbred maize was fertilized at 0, 101, and 202 kg N ha−1. Annual NO3 leaching losses were 7 kg N ha−1 higher in fields fertilized at 101 kg N ha−1 than in nonfertilized controls. Annual NO3 leaching losses to ground water between May 1995 and April 1998 from lysimeters fertilized at 202 kg N ha−1 averaged 88 kg NO3-N ha−1. Rye interseeded with inbred maize fertilized at 202 kg N ha−1 sequestered from 46 to 56 kg ha−1 of excess fertilizer N. Rye scavenged little residual fertilizer N in plots fertilized at 101 kg N ha−1. Well established rye cover crops in 1996 reduced NO3 leaching by as much as 65 kg N ha−1 when the previous crop was fertilized with 202 kg N ha−1. Therefore, rye cover crops sequestered substantial amounts of soil NO3 in heavily fertilized inbred maize fields.
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