Alum treatment of poultry litter: decomposition and nitrogen dynamics.

While the poultry industry is a major economic benefit to several areas in the USA, land application of poultry litter to recycle nutrients can lead to impaired surface and ground water quality. Amending poultry litter with alum [Al3(SO4)2 x 14H2O] has received considerable attention as a method of economically reducing ammonia volatilization in the poultry house and soluble phosphorus in runoff waters. The objective of this study was to characterize the effect of alum on broiler litter decomposition and N dynamics under laboratory conditions. Litter that had been amended with alum in the poultry house after each of the first four of five flock cycles (Experiment I) and litter that had been amended with alum after removal from a poultry house after the third flock cycle (Experiment II) were compared with unamended litter in separate studies. The litters in Experiment I were surface-applied to simulate application to grasslands, while the litters in Experiment II were incorporated to simulate application to conventionally tilled crops. The only statistically significant differences in decomposition due to alum occurred early in Experiment II and the differences were small. The only statistically significant differences in net N mineralization, soil inorganic N, and soil NH4+-N in either experiment was found in Experiment I after 70 d of incubation where soil inorganic N was significantly greater for the alum treatment. Thus, alum had little effect on decomposition or N dynamics. Results of many of the studies on litter not amended with alum should be applicable to litters amended with alum to reduce P availability.