NUTRIENT MANAGEMENT IN RAIN-FED AND IRRIGATED FARMING SYSTEMS

Authors: Sharpley, Andrew; Schmidt, John; HERGERT, GARY - UNIV OF NEBRASKA

Submitted to: Soil and Water Conservation Society
Publication Type: Book / Chapter
Publication Acceptance Date: 4/14/2005
Publication Date: 1/20/2007
Citation: Sharpley, A.N., Schmidt, J.P., Hergert, G.W. 2007. Nutrient management practices. In: Schnepf, M. and Cox, C., editors. Environmental Benefits of Conservation on Cropland the Status of Our Knowledge. Ankeny, IA: Soil and Water Conservation Society. p. 149-194.

Interpretive Summary: An interpretive summary is not required.

Technical Abstract: Managing nitrogen (N) and phosphorus (P) on farms in ways that maximize crop production and minimize environmental impacts involves a range of activities. These include careful planning of the amount (via soil and plant tissue testing), type, placement (e.g., broadcast, injection, and banding), and timing (e.g., spring, fall, and split applications) of nutrients applied as fertilizer or manure, so that as much of the applied N and P as possible is either removed by the crop or remains in residual forms that can be taken up by subsequent crops. Any N or P in excess of crop needs is susceptible to loss by leaching (mainly N) and surface runoff (mainly P). Thus, managing nutrients so they stay where they are applied also involved land practices that minimize leaching, runoff, and erosion potential, such as conservation tillage, contour and strip cropping, riparian or buffer areas, and critical source area treatment. For confined animal feeding operations, nutrient management also involves matching the amounts of N and P in feed with the animals’ requirement, as well as using less additives and crop hybrids that increase N and P absorption by the animal. The goal here is to decrease N and P excreted as manure, which can then be more efficiently recycled as an on-farm nutrient resource. The NRCS has developed standards on how to plan, implement, and maintain nutrient management conservation practices. Although the benefits of nutrient management to water and air quality are varied and well documented, their adoption is not simple, and has required incentives and, in some cases, regulatory measures. Additional research is needed to refine real-time plant N requirements and link this to site-specific variable-rate fertilizer application technology. Because nutrient losses occur from well defined and, for P, relatively small areas of a watershed, nutrient management will be of greater benefit to water and air quality if these critical sources and areas of loss are targeted. Most critically, research is required to determine, after nutrient management implementation, how long it will be before we see an environmental response and where would we expect to see the greatest or least response. These are the basic goals of the Conservation Effects Assessment Project – Watershed Assessment Studies (CEAP-WAS) (http://www.nrcs.usda.gov/technical/nri/ceap/), reviewed in this book.