
EPA Science Advisory Board	Background Information

Document Name	Nitrate-N in surface waters as influenced by climatic conditions and agricultural practices.
Document Author	Randall, G.W. Mulla, D.J.
Short Description	Journal of Environmental Quality 30:337-344.
Category	Subgroup 2: Characterization of Nutrient Fate-Transport-Sources
Publication Year	2001

Text:

Abstract: Subsurface tile drainage from row-crop agricultural production systems has been identified as a major source of nitrate entering surface waters in the Mississippi River basin. Noncontrollable factors such as precipitation and mineralization of soil organic matter have a tremendous effect on drainage losses, nitrate concentrations, and nitrate loadings in subsurface drainage water. Cropping system and nutrient management inputs are controllable factors that have a varying influence on nitrate losses. Row crops leak substantially greater amounts of nitrate compared with perennial crops; however, satisfactory economic return with many perennials is an obstacle at present. Improving N management by applying the correct rate of N at the optimum time and giving proper credits to previous legume crops and animal manure applications will also lead to reduced nitrate losses. Nitrate losses have been shown to be minimally affected by tillage systems compared with N management practices. Scientists and policymakers must understand these factors as they develop educational materials and environmental guidelines for reducing nitrate losses to surface waters.