Submitted to: CSA News
Publication Type: Popular Publication
Publication Acceptance Date: 9/27/2008
Publication Date: 1/1/2009
Citation: Cook, K.L., Rothrock Jr, M.J., Warren, J.G., Sistani, K.R. 2009. Alum affects ammonia-producing microorganisms in poultry litter. CSA News. 54(1):5.
Technical Abstract: Scientists at the USDA-ARS in Bowling Green, KY and in Fayetteville, AR are working to uncover the microbiology of ammonia production in poultry litter. Poultry litter is a valuable nutrient source for plants and microorganisms that contains high levels of protein, nitrogen, and other minerals. However, production of ammonia by microorganisms in litter leads to decreased poultry performance, malodorous emissions, and loss of poultry litter value as a fertilizer. Researchers have found that acidifying litter reduces ammonia emissions and increases nitrogen in the litter. Despite the fact that ammonia production in litter occurs as a result of microbial activity, little is known about the microbiology of the process. Therefore, the goal of the USDA-ARS study was to discover how the microbial populations, in particular ammonia producing microorganisms in poultry litter, respond to acidifying litter amendments such as alum. In a temporal study of poultry litter with or without 10% alum, the USDA-ARS researchers combined data from chemical (total N and NH4–N content of litter) and microbiological (total and ammonia-producing bacteria and fungi) analyses to show that there were significant changes in the microbial population in response to the administration of alum as an amendment in poultry litter. Results from the study were published in the November–December Journal of Environmental Quality. When treated with alum, the bacterial population in poultry litter was reduced by 50%, and bacterial ammonia producers decreased by 90%. In contrast, the fungal population increased more than three orders of magnitude in alum-treated poultry litter when compared with untreated litter. The shift in pH inhibited bacterial populations but selected for fungal organisms. The loss of organic nitrogen from alum-treated litter tracked with the increase in the fungal population. Therefore, the time-delayed onset of organic nitrogen loss in alum-treated poultry litters may be due to the selection for the less dominant, slower growing fungal population. These data suggest that alum reduces ammonia emissions by both biological (inhibition of ureolytic microorganisms) and chemical means (conversion of NH3 to NH4–N). This may explain why alum effectively reduces ammonia emissions. In a low pH, high-nitrogen environment where bacteria are inhibited, proliferation of fungi is not surprising and may explain the similarity in net nitrogen mineralization in untreated and alum-treated poultry litter, despite the inhibition of the bacterial population by alum addition. This new information will be used by scientists to develop more effective litter amendments that directly target ammonia producers. The ultimate goal is to find ways to inhibit both bacterial and fungal ammonia producers so that farmers are able to retain the nitrogen value of the litter and reduce the negative effect of ammonia production on the birds.