Optimizing soil and plant responses to land-applied manure nutrients in the Great Plains of North America

Animal manures are recognized as valuable sources of plant nutrients in cropping systems and also play a role in soil improvement through the input of organic matter. Using recent research examples from Saskatchewan and Colorado, this paper covers beneficial management practices for effective recycling of manure nutrients applicable to the Great Plains region of North America. Challenges in using animal manures as fertilizers include low nutrient content per unit weight, variability and availability of nutrient content, and a balance of available nutrients that often does not meet the relative nutrient requirements of the crop. Examples of imbalances that may arise requiring special management considerations include low available N content relative to available P for many solid manures, and low available S relative to N for some liquid manures. Application decisions are best supported by manure and soil analyses, with nutrient balance issues addressed by rate adjustments and the addition of supplemental commercial fertilizer to avoid deficiency or loading of specific nutrients. Placement of manure into the soil by injection or incorporation is desirable in that nutrient losses by volatilization and runoff are reduced and crop recovery is increased. Balancing the rate of nutrient application with crop requirement and removal over time is key to avoiding nutrient loading on soils receiving repeated applications of manure.