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Title: Nitrogen Leaching Index

item Delgado, Jorge

Submitted to: Encyclopedia of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2011
Publication Date: 12/13/2012
Citation: Delgado, J.A. 2012. Nitrogen Leaching Index. In: Sven Erik Jorgensen, Editor. Encyclopedia of Environmental Management. New York, NY: CRC Press Taylor & Francis Group. P. 1761-1767.

Interpretive Summary: The Nitrogen Index, which is available for download at the USDA-ARS website, has been tested and calibrated using data from a Mediterranean region of Spain, the North China Plain, Mexico, South America, and different sites across the USA. Results of these tests have shown that the Nitrogen Index is able to evaluate the effect of management of on residual soil nitrate, water leaching, nitrate leaching, and crop nitrogen uptake. Additionally, groundwater nitrate concentrations predicted by the Nitrogen Index have also been found to be correlated with measured groundwater nitrate concentrations. Although it is recommend that users get familiarized with the capabilities and limitations of the Nitrogen Index, the results from testing this tool across so many different agroecosystems, soils, management and weather suggest that it can be used as a tool to assess the risk of management practices on potential losses of reactive nitrogen, including nitrate leaching. Results also suggest that the Nitrogen Index can be as part of an ecological engineering approach to soil and water conservation planning. It is recommend that users get familiarized with the Index, and that if necessary they calibrate and/or validate the Index for their region. In 2010, INIFAP, a scientific research organization in Mexico, reported the Mexico Nitrogen Index as one of Mexico’s top five forage management achievements because of the tool’s usefulness in contributing to an assessment of the effects of nitrogen management on the potential for nitrogen losses such as nitrate leaching. There is potential to use this tool to assess the effects of management practices and to rank the risk as very low, low, medium, high, or very high. The Nitrogen Index can potentially be used as an indicator to assess the risk of nitrate leaching to the environment, so users and nutrient managers can then implement appropriate practices to reduce the reactive losses to the environment. This new tool and new approach shows promise for being used as an effective environmental conservation technology.

Technical Abstract: World agricultural production will have to increase significantly during the next few decades to keep up with the increasing demands for food brought about by a growing human population. Increases in agricultural production will be required not only to supply grain for a larger world population, but a significant increase in grain and forage production will be needed to meet the higher demand for meat and dairy products that will be created as the world population grows in size and as large populations such as those in India and China become more affluent. Nitrogen will be at the center of the world’s emerging sustainability challenges. Since in general across worldwide agroecosystems agricultural production is increased with nitrogen inputs and best nitrogen management practices, nitrogen will be an essential component of efforts to increase productivity and sustainability. Use of nitrogen fertilizer has contributed to increased agricultural production. However, at the same time, inputs of nitrogen also contribute to increased losses of reactive nitrogen from agricultural systems, losses which can have environmental impacts. Nitrate leaching has been reported to impact aquifers across the world, from the Northern China Plain, to the European region and South America, to across the USA. Nitrate leaching from tile systems has also been reported to contribute to impacts to water bodies and in some cases it has even been reported to contribute to the transport of nitrates from agricultural fields to coastal systems. Impact to domestic wells that are source of drinkable water has been reported for significant areas across the USA. A nitrate leaching index is a simple approach to estimating the risk of nitrate leaching to the environment. The Nitrogen Index can be used as an indicator and/or new ecotechnology to assess the risk of nitrate leaching for a given set of management practices under given weather, soils and off-site factors. The Nitrogen Index can potentially help users assess the risk of environmental impacts.