Rye Cover Crop and Nitrogen Fertilization Effects on Nitrate Leaching in Inbred Maize Fields

Abstract

Abstract 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 NO 3 leaching in inbred maize fields. Inbred maize was fertilized at 0, 101, and 202 kg N ha −1 . Annual NO 3 leaching losses were 7 kg N ha −1 higher in fields fertilized at 101 kg N ha −1 than in nonfertilized controls. Annual NO 3 leaching losses to ground water between May 1995 and April 1998 from lysimeters fertilized at 202 kg N ha −1 averaged 88 kg NO 3 ‐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 NO 3 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 NO 3 in heavily fertilized inbred maize fields.