|Poultry litter is an inexpensive source of plant nutrients and organic matter, but it is important to consider potential problems with its use as well. High rates of litter can result in extremely high soil test levels of some nutrients and sometimes leads to inconsistent results.
The first consideration is the level of phosphorus (P) in litter. Alabama has developed a Phosphorus Index that provides a guideline to the amount of phosphorus fertilizer that can be applied to a field. This index was established to try to lessen the possibility of nonpoint source pollution of surface waters from over application of manures and fertilizer. Factors affecting the P index include soil test P levels, application rate and method of P as well as field characteristics affecting erosion and possibility of stream or river contamination from field water runoff. Bottom line is that if the P index for a field is extremely high, no more P may be applied. Therefore it is important to carefully watch soil test levels and know how much P is being applied in order to prevent excessive buildup. Because of the ratio of nutrients in poultry litter, its continued use to provide nitrogen (N) to a crop can result in a buildup of P that could prevent its future use.
It is also important to consider that the form of nutrients in poultry litter may not be readily available to plants. Soil organisms must mineralize organic N before plants can use it. This can result in some degree of unpredictability of N availability. Care should be taken with cotton since high N levels late in the season can become a problem at harvest time.
It is also important to understand that overuse of poultry litter may also result in buildup of other nutrients, including metals like zinc.
This can be especially important to peanut growers