Nitrogen is the nutrient that is most affected by the various components of manure management systems. As the term suggests, total nitrogen is an expression of all of the nitrogen contained in the manure. Not all of this nitrogen will be available to the crop in the year of application. Ammonia is the nitrogen form that is available to the crop. The actual amount of ammonia available to the crop is calculated by subtracting volatilization losses during application from the amount of ammonia in the manure.
Organic nitrogen is calculated by taking the difference between total nitrogen and ammonia.
This form of nitrogen is slowly released to the crop and can have a significant impact in the nitrogen-supplying power of the soil if allowed to build up after several years of repeated manure applications. Phosphorus Phosphorus is usually found in manure in smaller quantities than nitrogen. However the amount present relative to crop production requirements is higher than nitrogen in some cases. That is, if manure is applied at rates to satisfy crop nitrogen requirements, then a surplus amount of phosphorus may have been applied. The use of phytase in the feed ration is an effective way to reduce this imbalance.