Sustainable nutrient management for pig and cattle manure applied to annual and forage cropping

Introduction Application of livestock manure provides nutrients for crop production and can also improve soil quality. However, the availability of nutrients in manure is difficult to predict. Therefore, livestock manure is frequently under or over-applied with respect to crop nitrogen and phosphorus requirements. In cases where the availability of nutrients is less than expected, application rates may be insufficient to meet a crop's nutritional requirements, whereas application of manure nutrients in excess of crop requirements can result in excessive accumulation of nutrients in soil and an increased risk of nutrient loss to ground or surface water. Therefore, an accurate estimate of nutrient availability from manure is required, not only to decrease fertilizer requirements and costs to producers but also to minimize risk to the environment.