The major route for the disposal and/or utilization of poultry manure has been its application to cropland. Disposal is when large amounts of manure are applied to the land without regard to soil fertility and projected cropfertilization needs. Utilization is when the manure applied is calculated to meet the needs for soil fertilizer elements used in crop production. This alternative will remain as a major method of dealing with poultry manure, but increasing emphasis must be placed on utilization for crop production and not on disposal.
Over-application of poultry manure to cropland can lead to problems such as surface and ground water pollution and esthetic problems with odors and insects. Reduced crop yields could also result from over-application due to soil accumulation of both macro and trace minerals. The most serious problem generated by excessive manure application is surface and ground water pollution with nitrates that originate from oxidation of nitrogen contributed by the manure. Also, important ecological problems can result from the discharge of ammonia, phosphates and organic matter that results in increased biological oxygen demand in waterways. Low levels of oxygen in the water, in combination with toxic levels of ammonia, will cause the death of fish and other aquatic lifeforms. Thus, excessive manure application has the potential for damaging the environment in lakes and streams.
As a crop fertilizer, poultry manure should be limited to amounts needed for crop production so not to contribute significantly to ground or surface water pollution. This means that some concentrated poultry production units need to find additional land area for utilization of their poultry manure output or consider other alternatives for poultry manure utilization that will permit recycling of manure products and their transport for use in other locations.