Cover Crops to Reduce Nitrate Losses

Planting cover crops is a traditional soil-building practice that deserves new consideration in our modern cropping systems. A new era for cover crops is being driven in part by higher fertilizer and energy prices, water quality concerns, soil compaction, and declines in soil quality and organic matter. Winter cover crops grown after corn and soybeans can build soil tilth and trap nitrate that would otherwise leach out of the soil into drain tiles during fall, winter, and early spring. Water quality is thereby improved by keeping nutrients in the soil rather than in drainage waters. Some of the nitrate taken up by the cover crop will be recycled to the next crop, while some will help build soil organic matter over a longer term. The amount of N trapped by the cover crop depends on the particular plant as well as the amount of growth that occurs in fall and/or spring. The amount of N released for the next crop depends not only on the uptake but also on the timing of cover crop termination, the age/stage of the cover crop at termination, and subsequent weather. Specific recommendations for potential changes in nitrogen fertilizer rates as a result of growing trap crops require more research and demonstration results across a number of soils and years.

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Eileen  Kladivko Professor of Agronomy
Purdue University
kladivko@purdue.edu

Dr. Eileen J. Kladivko is Professor of Agronomy at Purdue University, where she teaches and does research in soil physics, soil biology, and soil management. Her overall research focus has been to identify soil management systems that improve environmental quality and promote agricultural sustainability. Specific research areas have included tile drainage and water quality; the interactions of earthworms, soil management, and soil physical properties; conservation tillage and cover crops for soil quality improvement; and preferential flow of chemicals through soils.