An Estimate of the Source and Uptake of Nitrogen in Continuous No-Till Com Grain Production

The U.S. Environmental Protection Agency (EPA) has established a maximum nitrate nitrogen (NO3-N) content of 10 parts per million (ppm) for safe drinking water. Because of this, the effect of commercial nitrogen (N) fertilizers in agricultural production as a contributor of NO3-N to surface and groundwater is now being widely examined. Since corn production in the US is the largest single source of fertilizer N use, averaging perhaps 100-150 lbs N/A on the 70-80 million acres of corn produced annually, an understanding of N utilization and losses in corn production is helpful in determining the role of N fertilization of corn as a potential groundwater contaminant. Concerns are greatest in areas where a large proportion of the landscape is used for corn production in any given year. For Kentucky as a whole, only 5.4% of the total land area was used for corn in 1993, ranging from less than 1% in eastern Kentucky to over 15% in parts of western Kentucky. Some individual counties were higher (Union 36%, McLean 27%, Henderson 26%, Daviess 26%, Webster 21%). At an estimated N use of 150 lbs/A, total N used on corn in these counties was 5,925; 3,300; 5.475; 5, 700 and 3,375 tons, respectively. In order to provide for a better understanding of what happens when N is used for corn production, an estimate was made of source and uptake of N in a continuous no-till corn production system