Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 8/14/2002
Publication Date: N/A
Technical Abstract: Subsurface tile drainage has made annual cropping possible on about 42 million acres of cropland in the North Central USA. Tile drainage contains nitrate and other dissolved ions, which can impair surface water, and has been implicated in development of the hypoxic zone in the Gulf of Mexico. Annual losses from the predominant corn-soybean crop rotation are typically 15 to 60 kg N/ha. Excess soil water accumulates when evapotranspiration is smaller than effective precipitation. Alternative cropping systems are among the various strategies and tactics being tested to reduce nitrate loading of the Mississippi River. Perennial forages or native prairie species are the most likely to achieve this goal. Some of these species use water and absorb nitrate over a longer time period than corn and soybean. The superiority of perennial crops in reducing nitrate losses has been shown, but lack of equipment and markets, lower government support, and logistical impediments are hindrances to expanded perennial plantings. A potentially feasible, but untested, idea is to plant narrow strips of perennial grasses or legumes directly over tile drains to serve as 'biocurtains' that remove nitrate lost from adjacent annual cropland. Cover crops provide a possible means of reducing nitrate losses where they can be reliably established and produce enough dry mass. Their effectiveness is directly related to their growth. Seeding and termination costs, sensitivity to carryover herbicides, and lack of reliable methods to establish stands by early autumn are impediments to cover crop use. Diversifying the corn-soybean cropping system with either perennial forages or cover crops has the potential to help farmers achieve environmental goals.