Regulatory agencies in some states may require that manure be applied with a phosphorus limit rather than a nitrogen limit. The poultry litter will be surface-applied with no incorporation. The field to be spread has received similar poultry litter applications in prior years. Because the field has had poultry litter spread on it in prior years, the organic nitrogen available this year will be about 75 percent of the organic nitrogen applied this year. If the field had not been spread with poultry litter in prior years, only about 50 to 60 percent of the organic nitrogen spread this year would be available this growing season.
Ammonia nitrogen is much more subject to field losses than is organic nitrogen.
From 20 to 80 percent of applied ammonia nitrogen may not be available to plants, depending on timing of the application and on soil and climatic conditions. Generally, samples and analyses should be obtained as close to the spreading activity as reasonably possible. However, nutrient levels in manure storage structures do not change rapidly, and an elapsed time of 2 to 3 weeks is not likely to be critical. Seasonal changes do occur, however, and a manure analysis obtained in the spring should not be used for a fall application. Since the spreading activity takes place at the same time, or very closely following agitation, laboratory results may not be available when the manure is spread.