Crop Management and Corn Nitrogen Rate Effects on Nitrate Leaching

• Published in: Journal of environmental quality 2000-07, Vol.29 (4), p.1095-1103
• Main Authors: Andraski, T. W., Bundy, L. G., Brye, K. R.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Cereal crops; Crop management; Fundamental and applied biological sciences. Psychology; Leaching; Soil and water pollution; Soil science
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2000.00472425002900040009x

Excess N use in crop production is often identified as a major contributor to NO3 enrichment of ground water. Little information is available to show the specific relationships between crop management systems and N fertilizer use on the amounts of NO3 lost by leaching. This study determined the effect of several cropping systems and N rates, providing a range of N availability to corn (Zea mays L.), on soil water NO3 concentrations and leaching below the root zone. Four cropping‐manure management systems were established in 1993 and 1994 (8‐site years) at Arlington, WI, on a Plano silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudoll). Ammonium nitrate (0 to 204 kg N ha−1 in 34‐kg increments) was broadcast at the time of corn planting. Economic optimum N rates (EONR) for corn ranged from 0 to 150 kg ha−1 depending on site‐year. Soil water NO3 concentrations were determined for 18‐mo using porous‐cup samplers installed at a 120‐cm depth in the 0 and 204 kg N ha−1 treatments. Nitrate N concentrations in the samplers increased as the amount of N applied in excess of the observed EONR increased. Predicted soil water NO3−N concentration at EONR was 18 mg L−1. Average NO3−N concentrations were 50 kg N ha−1 below the EONR and >20 mg L−1 where fertilizer N rates were >50 kg N ha−1 above the EONR. Total NO3−N leaching estimates based on water budget data and soil water NO3 concentrations for the 18‐mo study period ranged from 3 to 88 kg ha−1 depending on crop and manure management system, N fertilizer rate, amount of water drainage, and time of drainage event relative to treatment establishment. An end‐of‐season soil NO3 test appears to be capable of evaluating corn N management practices and indicating the amount of excess N fertilizer applied that may be leached from the root zone. These results illustrate the direct relationship between NO3 loss by leaching and N application rates that exceed crop needs.