Assimilation Versus Accumulation of Macro- and Micronutrients in Soils: Relations to Livestock and Poultry Feeding Operations

Abstract

Nutrient management is an integral part of profitable agrisystems, but in some areas of the United States, continued applications of fertilizer and manure nutrients in excess of crop requirements have led to a buildup of nutrient concentrations that are of environmental concern. Proper use of nutrients in livestock manures is becoming more critical for sustainability of concentrated animal feeding operations (CAFO) because new environmental regulations require that nutrients be properly applied and managed. Losses of nutrients, such as N and P can be reduced by refining the rations fed, increasing nutrient retention by livestock, moving manures from areas of surplus to deficiency, finding alternative uses for manure, using cropping and haying systems that remove excess nutrients, and using conservation practices, such as limited tillage, buffer strips, and cover crops to limit runoff and leaching. Whole farm nutrient balances are useful for educating producers about quantities of nutrients being managed and the flow of nutrients, but they can also be misleading because of spatial factors, such as uneven nutrient application that introduce environmental risks that may not be noted with a whole-farm nutrient balance. Manure utilization plans also need to deal with nutrients that potentially leave the field or production area in route to sensitive ecosystems.