Manure Management to Improve Nutrient Use Efficiency and Environmental Quality.

Manure from livestock operations can be a valuable source of N, P, K, and micronutrients for crop production, but careful management is important to maximize nutrient use efficiency and minimize N and P losses that can adversely impact the environment. Volatilization of NH₃-N, the largest N loss potential, can be controlled by timely incorporation by tillage or use of injection or other application techniques. These practices, combined with optimum timing and rate of application (based on nutrient analysis and crop need) can maximize efficiency of crop use and minimize nitrate leaching losses to achieve fertilizer N equivalence of as much as 50%. Manure N conservation not only provides a direct economic savings but results in a N:P ratio that more closely meets crop needs. Crop availability of manure P is typically equal or somewhat lower than fertilizer P. The primary environmental concern with manure P is loss via runoff and, in some cases, leaching to surface waters. Runoff losses of manure P are a function of P content, especially soluble P, application rate, placement, and timing, as well as a number of soil and site characteristics and management practices that affect transport. Managed properly, manure can not only be an important nutrient source for crops but can also contribute to improved soil quality and long-term soil productivity.