Nitrogen Cycling in Stored Poultry Litter.

Poultry litter (PL) is a waste material produced in large quantities by the poultry production industry (~2.0 Mg annually in the State of Georgia).  It has value as an organic soil amendment approximately equivalent to a 1.5-2-2 chemical fertilizer.  Between the time PL is removed from the poultry house and the appropriate time for application to crops, it is often placed in temporary storage.  During this period, a portion of the nitrogen (N) may be lost due to volatilization of ammonia.  A fraction of the remaining organic N may continue to mineralize and be available to crops after application.  The mineralizable fraction of N in PL arises largely from easily hydrolysable compounds such as urea, uric acid, proteins, and nucleic compounds.  The transformations these compounds undergo in PL during storage and their rates are poorly understood, yet are important in predicting the N-fertilizer value of PL applied to crops.

Measurement of N forms over time in stored PL have shown that uric acid concentrations remain stable for several weeks before declining due to conversion to mineral N.  Controlled laboratory incubation experiments have shown that there may be some cycling (temporary immobilization) of N from mineral to organic form during early production of biomass as indicated by increases in uric acid-, xanthine-, and ammonium-N concentrations.  The pattern of increase and decline in these organic N compounds is affected by water content and temperature.