The effect of an acidified-gypsum mixture on broiler litter urease-producing bacteria and nitrogen mineralization.

Ammonia (NH ) volatilization from broiler (Gallus gallus domesticus) litter is a microbially mediated process that can decrease bird productivity and serves as an environmental pollutant. The release of NH is strongly influenced by the pH of litter. Flue-gas desulfurization gypsum (FGDG) has been suggested as a potential amendment to reduce NH volatilization due to the pH buffering capacity of calcium carbonate (CaCO ) precipitation. However, its effect on litter pH is not as pronounced as acidifying agents, such as aluminum sulfate (alum). The main objective of our study was to develop an acidified-FGDG amendment that has a more pronounced effect on litter pH and NH volatilization than FGDG alone. We conducted a 33-d incubation in which litter pH, NH volatilization, nitrogen mineralization, PLUP-ureC gene abundance, and CaCO precipitation were measured. Treatments in the study included: broiler litter (BL), broiler litter + 20% FGDG (BL+FGDG), broiler litter + FGDG-alum mixture (BL+FGDG+A6), broiler litter + 6% alum (BL+A6), and broiler litter + 10% alum (BL+A10). Our FGDG+alum amendment decreased litter pH (0.68 pH units) and PLUP-ureC gene abundance (>1 log) compared with FGDG alone and the control (p < .05). This led to a 25% decrease in cumulative NH loss after 33 d. The addition of FGDG alone did not have an effect on litter pH (p = .36) or cumulative NH loss (p = .29) due to a lack of significant CaCO precipitation. Treating litter with 6 and 10% alum was the most effective amendment for reducing pH and cumulative NH loss.