GROUNDWATER IMPACTS 57 GROUNDWATER IMPACTS Effects of cover crops on groundwater quality

Cover cropping is a practice that can benefit soil-crop sys-tems in several ways: increasing nitrogen (N) supply for the next crop, reducing soil erosion, improving soil physical prop-erties, and conserving nutrients. Cover cropping dates back to ancient agriculture, reportedly as far back as 3,000 years to the Chou Dynasty in China (25,38), where cover crops were used to improve soil productivity. In colonial periods, winter cover crops of clover or hairy vetch (Vicia villosa L.) were recommended by Thomas Jefferson in Virginia to supply N to the next crop (4). Winter cover crops of rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and hairy vetch were systematically evaluated as N sources for cotton (Gossypium hirsuturn L.) in Alabama as early as 1898 (9). A summary of the excellent work of agricultural scientists in the early 1900s is provided in Pieters ' compilation of literature (38). This work emphasized the benefits of increasing N availability to the next crop. Later in this century (1930-1945), the role of cover crops in conserving N against leaching was studied. Reported lysimeter work (7, 22, 32) clearly shows that winter cover crops can significantly reduce nitrate (NO,) losses in water percolating through soil. Today, NO, losses from agricultural land into groundwater are a conem to society, agriculture producers, and farm techni-cal advisors. The agricultural community is being asked to de-J. J. Meisinger is a soil scientist, Environmental Chemistry Laboratory