Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2003
Publication Date: 3/28/2004
Citation: Rotz, C.A. 2004. Management to reduce nitrogen losses in animal production. Journal of Animal Science. 82(E. Suppl.):E119-E137.
Interpretive Summary: Nitrogen is an essential element in animal production. Large quantities are required for the growth of feed crops. Nitrogen incorporated into crops, primarily in the form of protein, is then an essential feed component for animal growth and development. Most of this nitrogen consumed is then excreted by the animals providing manure nutrients essential for crop growth. The problem in this cycling of nitrogen is that large losses to the environment occur, which contribute to degradation of the environment. A review of recent research work was done to summarize and quantify nitrogen losses for various animal production strategies and to evaluate options available for reducing these losses. Improving nitrogen use on the farm must begin with the animal. By improving the balance of nutrients in the diet to reflect that required by the animal, we can reduce the amount of excreted nutrients. Improving animal productivity can also help. Even when good management practices are used to minimize nitrogen excretion, large quantities remain in the manure. A large portion of this excreted nitrogen can quickly transform to ammonia, which readily volatilizes into the atmosphere. Volatile loss begins very soon after excretion, and it continues until the remaining manure nutrients are incorporated into the soil. Management practices can reduce volatile loss, but implementation often remains a challenge due to economic and labor constraints. A whole-farm approach is needed to manage nitrogen loss over all farm processes. If technology is used to reduce the volatile loss in the housing facility, this ammonia nitrogen retained will simply be lost during manure storage and field application if appropriate measures are not taken to reduce loss in these processes. If steps are taken to maintain the nitrogen until it is incorporated into the soil, leaching and denitrification losses of soil nitrogen will increase if that additional nitrogen is not applied at the appropriate amount and time and in the appropriate manner for crop uptake. By equally managing all parts of the farm, nitrogen losses to our environment can be reduced while maintaining or improving farm profit. Future farms will require these new technologies and management strategies to reduce or eliminate the adverse environmental affects of nitrogen loss.
Technical Abstract: Reduction of nitrogen (N) loss in animal production requires whole-farm management. Reduced loss from one component of the farm may be negated in another component if all components are not properly managed. Animal excretion of N can be reduced by improving the balance of protein or amino acids fed to that required by individual animals or animal groups or by improving production efficiency. Management to increase milk, meat, or egg production normally improves efficiency by reducing the maintenance protein required per unit of production. Large losses of N occur in manure handling through ammonia and nitrous oxide emissions to the atmosphere and nitrate leaching to ground water. Floor design and manure collection procedures influence volatile losses in the housing facility. Frequent flushing of floors provides some reduction in ammonia loss, and experimental methods that separate feces and urine on the floor provide up to a 50% reduction. Manure storage units improve application efficiency and allow for better timing of nutrient applications to fields to match crop needs. Substantial N loss can occur during storage primarily through volatalization of ammonia. Use of an enclosed tank can nearly eliminate this loss, but maintaining a natural crust on the manure surface in an open tank is almost as effective and a more economical technique. Irrigation and surface spreading of manure without soil incorporation often results in the loss of all remaining ammonium N (typically 20-30% of remaining total N), through volatilization as ammonia. Rapid incorporation and shallow injection methods reduce this loss by at least 50%, and deep injection into the soil essentially eliminates this loss. For grazing animals, excessive loss can be avoided by not overstocking pastures and avoiding late fall and winter grazing. Even with reduction of volatile losses between the animal and the soil substantial leaching and denitrification losses from the soil can still occur if appropriate managment practices are not followed. Use of a crop rotation that can efficiently recycle these nutrients and applying N near the time it is needed by crops reduces the potential for further loss. Maintaining the proper number of animals per unit of land available for manure application is always critical for efficient recycling of N with minimal loss to the environment.