Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 7/15/2001
Publication Date: N/A
Citation: Interpretive Summary: Long-term use of manure from concentrated animal feeding operations has resulted in excess soil nutrient levels, which has contributed to degradation of surface and ground water quality. Manure is a byproduct of animal agriculture that is costly (and often disagreeable) to distribute on the land. In this report, we have summarized the literature and current research on manure use and we propose research, education, and policy approaches to improving manure use and protecting surface and ground water. These results are meant to help guide future decision-making in Minnesota to develop profitable and environmentally sustainable systems of animal agriculture.
Technical Abstract: Animal production is growing in Minnesota and animal densities are increasing. There are two main driving forces at work when manure utilization is considered, "on farm" profitability and negative "down stream" impacts. At times economic and environmental quality goals compete. This report addresses the value of manure and the potential negative environmental effects of manure use on cropland. The nutrient value of manure for crop production depends on the site-specific reserve of plant- a ble soil nutrients, nutrient concentrations in manure, and crop nutrient demand. Under conditions of adequate soil P, K, or micronutrients, there is little or no economic value associated with these elements in applied manure. The uncertainty associated with potential N losses and plant availability and the recognized difficulty in applying manure evenly at the desired rate are reasons why farmers take low N credit from manure. Continued manure application to meet N needs of crops for maximal crop production can increase soil test P to values where no additional P is required. Risks posed to surface water by high soil test P vary with many landscape and management factors. Soil and water conservation techniques are important components to environmentally sound farming systems in areas near surface water where slopes are steep and erosion potential is high. The best environmental strategy is to use P-based rates with supplemental fertilizer N where there is high risk of environmental impact from P (i.e., a high P index), and to use N based rates where the P risk is low. A series of recommendations are included for research, education, and policy approaches to protecting water resources from manure nutrients.