Gw. Randall et Dj. Mulla, Nitrate nitrogen in surface waters as influenced by climatic conditions and agricultural practices, J ENVIR Q, 30(2), 2001, pp. 337-344
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 drainag
e water. Cropping system and nutrient management inputs are controllable fa
ctors that have a varying influence on nitrate losses. Row crops leak subst
antially greater amounts of nitrate compared with perennial crops; however,
satisfactory economic return with many perennials is an obstacle at presen
t. 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 a
pplications will also lead to reduced nitrate losses. Nitrate losses have b
een shown to be minimally affected by tillage systems compared with N manag
ement practices. Scientists and policymakers must understand these factors
as they develop educational materials and environmental guidelines for redu
cing nitrate losses to surface waters.