PRINCIPLES FOR MANAGING NITROGEN LEACHING

Authors: Meisinger, John; Delgado, Jorge

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2002
Publication Date: 8/10/2002
Citation: MEISINGER, J.J., DELGADO, J.A. PRINCIPLES FOR MANAGING NITROGEN LEACHING. JOURNAL OF SOIL AND WATER CONSERVATION. 2002.

Interpretive Summary: Controlling N leaching presents a challenge to nutrient managers who must develop nutrient management plans that consider rate and application strategies that account for soil properties, hydrology, and crop- tillage systems of a specific site. Major leaching events occur when soil nutrient concentrations are high and water is moving through the soil profile. The universal tools for managing nutrient leaching include understanding the soil-crop-hydrologic cycle, avoiding excess nutrient applications, and applying nutrients in-phase with crop demand. Specific cropping system tools for managing leaching include use of grass cover crops, adding a legume to a rotation, and adding crops that more fully utilize the soil- water resources. The primary water management tool to reduce nutrient leaching is irrigation scheduling. Other approaches to reduce leaching include use of riparian zones and conservation reserve program areas. Site emonitoring tools such as the pre-sidedress soil nitrate test, leaf chlorophyll meter, and tissue nitrate tests are useful in identifying N sufficient sites and avoiding excess N rates. Real-time monitoring techniques, such as the N Reflectance Index, can be combined with global positioning systems and geopraphic information systems to produce maps of the crop N status. Crop simulation models can also be used to integrate N and water dynamics during a growing season, and provide guidance in designing practices for reducing nutrient leaching. The application of the above nutrient management tools to fields, or specific management areas within a field, will improve crop nutrient recoveries with subsequent reductions in nutrient leaching.

Technical Abstract: Managing leaching presents a challenge to nutrient managers who must develop nutrient management plans that consider rate and application strategies that account for soil properties, hydrology, and crop-tillage systems of a specific site. Nitrogen (N) leaching losses from commom grain -production systems typically range from 10-30% of the total N input. Major leaching events occur when soil N concentrations are high and water is moving through the soil profile. The universal tools for managing N leaching include understanding the soil-crop-hydrologic cycle, avoiding excess N applications, and applying N in-phase with crop demand. Specific cropping system tools for managing leaching include use of grass cover crops, adding a legume to a rotation, and adding crops that more fully utilize the soil- water resources. The primary water management tool to reduce N leaching is irrigation scheduling. Other approches to reduce leaching include use of riparian zones and conservation reserve program areas. Site monitoring tools such as the pre-sidedress soil nitrate test, the leaf chlorophyll meter, and tissue nitrate tests are useful in identifying N sufficient sites and avoiding excess N rates. Rea-time monitoring techniques, such as the N Reflectance Index, can be combined with global positioning systems and geographic information systems to produce maps of the crop N status. Crop simulation models can also be used to integrate N and water dynamics during a growing season, and provide guidance in designing practices for reducing N leaching. The application of the above N management tools to fields, or specific management areas within a field, will improve crop N recoveries with subsequent reductions in N leaching.