Rye cover crop and nitrogen fertilization effects on nitrate leaching in inbred maize fields

Nitrate leaching from maize (Zea naps 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 seas 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 ks 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.