Long-term applications of untreated and alum-treated poultry litter drive soil nitrogen concentrations and associated microbial community dynamics

Abstract

Aluminum sulfate (alum) treatment retains ammonia in poultry litter, potentially altering nitrogen (N) cycling after application to soil. The objective of this research was to assess if 8 and 9 years of annual application of untreated or alum-treated poultry litters or ammonium nitrate have resulted in detectable differences in N concentrations and cycling in soil. Soil N concentrations, β-glucosaminidase activity, and ammonia oxidizer community richness were measured prior to, 10 days, and 1 and 6 months following application in years 8 and 9 in soil receiving either 2.24 (low rate) or 8.96 Mg litter ha−1 (high rate) or 65 or 260 kg N ha−1 (approximately equivalent N rates) of ammonium nitrate. There were few effects when fertilizers were applied at the low rate, but soil N did increase in all treatments relative to the control. Soil N, microbial biomass N, and β-glucosaminidase activity were significantly higher in the alum-treated and untreated poultry litter when applied at the high rate compared to other treatments. Soil inorganic N increased significantly 10 days following application with the high rate of alum-treated litter and ammonium nitrate but not with untreated poultry litter. Ammonia oxidizer community compositions in the high rate of alum-treated and untreated poultry litter treatments were similar to each other and more closely related to the community in the ammonium nitrate treatment than the control. All fertilizers applied at the high rate altered the nitrifier community richness; however, the inputs of both poultry litters increased microbial biomass and enzyme activity, indicators of soil quality.