Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2010
Publication Date: 9/1/2010
Citation: Rothrock Jr, M.J., Cook, K.L., Warren, J.G., Eiteman, M.A., Sistani, K.R. 2010. Microbial mineralization of organic nitrogen forms in poultry litters. Journal of Environmental Quality. 39:1848-1857. Interpretive Summary: Ammonia volatilization from poultry houses can negatively affect not only the health and well-being of both the birds and human workers, but also the health of the surrounding environment. To combat this, poultry litter (the ammonia source) is typically amended with dry acids to reduce the pH of the litter, inhibiting ammonia volatilization. Considering little is known about the microbes (the ammonia producers) in these acidified poultry litter systems, laboratory incubations were performed to determine (1) the differential effect of commonly-used acidifiers (Al+Clear®, PLT®, Poultry Guard®) on microbial populations and (2) how acidification specifically affects the microbial populations responsible for organic N mineralization, and subsequent ammonia production. While all three acidifiers produced similar effects within the litter, there was at least a two-week delay in the microbiological responses using PLT®. Acidification selected for fungal populations, while reducing bacterial populations, and caused a 2- to 4-week delay in the mineralization of the major sources of organic N in the litter (uric acid and urea). These delays in organic N mineralization directly correlated with shifts from bacterially-dominated (under normal, non-acidified conditions) to fungally-dominated microbial communities. These results demonstrate the vital role of fungi in the mineralization of organic N in the low-pH, high-N environments, and the activity of these fungi should be considered in best management practices to reduce ammonia volatilization from acidified poultry litter.
Technical Abstract: Ammonia volatilization from the mineralization of uric acid and urea has a major impact on the poultry industry and the environment. Dry acids are a common management practice to reduce ammonia emissions from poultry houses, however little is known about how acidification affects the litter biologically. The goal of this laboratory incubation was to compare the microbiological and physiochemical effects of dry acid amendments (Al+Clear®, PLT®, Poultry Guard®) on poultry litter, and specifically correlate uric acid and urea contents of these litters to the microbes responsible for their mineralization. While all three acidifiers produced similar effects within the litter, there was at least a two-week delay in the microbiological responses using PLT®. Acidification of the poultry litter resulted in >3 log increases in total fungal concentrations, with both uricolytic (uric acid degrading) and ureolytic (urea degrading) fungi increasing by >2 logs within the first 2 to 4 weeks of the incubation. Conversely, total, uricolytic and ureolytic bacterial populations all significantly declined during this same time period. While uric acid and urea mineralization occurred within the first 2 weeks in the normal litter, acidification resulted in delayed mineralization events for both uric acid and urea (2- and 4-week delay, respectively) once fungal cell concentrations exceeded a threshold level. Therefore, fungi, and especially uricolytic fungi, appear to have a vital role in the mineralization of organic N in the low-pH, high-N environments, and the activity of these fungi should be considered in best management practices to reduce ammonia volatilization from acidified poultry litter.