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High litter moisture content suppresses litter ammonia volatilization

Miles, D.M., Rowe, D.E., Cathcart, T.C.
Poultry science 2011 v.90 no.7 pp. 1397
water content, broiler chickens, poultry manure, ammonia, volatilization, temperature, gas production (biological), gas emissions, animal housing, air quality
With global food demand expected to increase by 100% in the next 50 yr, urgency to combine comprehensive strategies for sustainable, efficacious, and environmentally sensible agronomic practices has never been greater. One effort for US meat bird management is to reduce NH₃ volatilization from litter to create a better growing environment for the birds, improve production efficiency, retain N in litter for fertilizer value, and negate the detrimental environmental impacts of NH₃ loss to the air. To derive the fundamental effects of temperature and moisture on litter NH₃ volatilization over the range of conditions found in commercial houses, experiments were conducted using commercial broiler litter that had moisture contents of approximately 20 to 55% while controlling temperatures ranging from 18.3 to 40.6°C. Litter samples (100 g) were placed in 1-L containers that received humidified air at approximately 113 mL/min. Volatilized NH₃ in exhaust air was captured in H₃BO₃ traps. Ammonia loss (log₁₀ transformation) was modeled via an equation using linear coefficients for temperature and moisture, an interaction term for temperature x moisture, and a quadratic term for moisture. The surface responses resembled parabolic cylinders, indicating a critical moisture level at which NH₃ no longer increases but is diminished as moisture continues to increase. The critical moisture level lies between 37.4 and 51.1% litter moisture, depending on the temperature. An increase in temperature consistently increased NH₃ generation. When the temperature extremes were compared, the maximum NH₃ was up to 7 times greater at 40.6 vs. 18.3°C. The upper moisture limit at which NH₃ release is maximized and subsequently arrested as moisture continues to increase had not been defined previously for commercial broiler litter. The poultry industry and researchers can use these results as a decision tool to enable management strategies that limit NH₃ production.