Livestock manure is considered a waste product from the perspective of the animal operation, but it can be an important resource for crop production by providing valuable nutrients and enhancing soil quality. However, manure application to cropland can also have adverse environmental effects, in particular ammonia and greenhouse gas emissions and impairment of surface and ground water quality. The benefits of manure can be enhanced and the potential environmental risks minimized by employing improved manure and soil management practices (Sharpley et al., 1994; Jokela et al., 2004). In this article we discuss the results of integrated research to evaluate several of these “best management practices” for their effect on runoff P losses: a) prompt incorporation of manure, aimed at controlling N losses by ammonia volatilization and protecting manure from runoff losses of P and N, b) application of manure at rates that do not exceed crop nutrient need (typically N or P, depending on crop needs and soil P test level), c) avoiding build-up of soil test P to excessive levels can contribute to runoff P losses even if manure and fertilizer are not applied, and d) eliminating unnecessary P supplementation of dairy diets, a practice that can have economic benefits and can help balance whole-farm P budget, thereby helping prevent soil P build-up.
Soil Science Extension
University of Wisconsin Madison