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United States Department of Agriculture

Agricultural Research Service

Title: Nitrogen Leaching Management

Authors
item Meisinger, John
item Delgado, Jorge
item Alva, Ashok

Submitted to: Encyclopedia of Soils in the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 29, 2003
Publication Date: June 15, 2006
Citation: Meisinger, J.J., Delgado, J.A., Alva, A.K. 2006. Nitrogen leaching management. Encyclopedia of Soils in the Environment. 2: 1122-1124.

Interpretive Summary: Nitrate leaching occurs when the soil nitrate-nitrogen concentrations are high and water moves beyond the root zone. Leaching losses in modern agriculture commonly account for 10-30% of the nitrogen additions. Leaching can contribute to nitrate enrichment of groundwater, which has a health advisory limit of 10 mg nitrate-nitrogen per liter. Leaching also contributes to eutrophication of surface waters, that can lead to the development of hypoxic zones in receiving waters like the Gulf of Mexico. Managing leaching requires development of site-specific practices that should be based on: understanding when leaching events occur for the site's soil-crop-hydrologic cycle, applying a rate of nitrogen to meet expected yields with adjustments for other nitrogen inputs, and timing nitrogen applications in phase with crop demand. Specific approaches to reduce leaching include adjusting irrigation inputs according to the site's water needs, employing cropping systems such as cover crops and deep-rooted crops, developing off-field areas like riparian zones, utilizing within-season monitoring tools such as the leaf chlorophyll meter and the pre-sidedress soil nitrate test, use of real-time sensors based on red and near infra-red reflectance, and employing remote sensing with geographic information systems and simulation models to identify the best combination of practices to control leaching within a field. Application of a specific combination of the above practices should increase crop nitrogen recovery and reduce the leaching of nitrate into the environment.

Technical Abstract: Nitrate leaching occurs when the soil nitrate-nitrogen (NO3-N) concentrations are high and water moves beyond the root zone. Leaching losses in modern agriculture commonly account for 10-30% of the nitrogen (N) additions. Leaching can contribute to nitrate enrichment of groundwater, which has a health advisory limit of 10 mg NO3-N/L, and to eutrophication of surface waters that can lead to the development of hypoxic zones in receiving waters. Managing leaching requires development of site-specific practices that should be based on: understanding the soil-crop-hydrologic cycle, applying a rate of N to meet expected yields, and applying N in phase with crop demand. Specific approaches to reduce leaching include adjusting irrigation inputs according to site water needs, employing cropping systems that fully utilize soil-water resources such as cover crops and deep-rooted crops, developing off-field N conservation areas like riparian zones, utilizing within-season monitoring tools like the leaf chlorophyll meter and the pre-sidedress soil nitrate test, use of real-time sensors based on red and near infra-red reflectance, and employing remote sensing with geographic information systems and simulation models to identify the best combination of practices to control leaching on small areas within a field. Application of a specific combination of the above practices should increase crop N recovery with concomitant reductions in NO3-N leaching.

Last Modified: 11/22/2014