PSXI-16 A multiple flux chamber system to evaluate nutritional strategies for beef cattle to mitigate ammonia emission potential of manure.

摘要

A laboratory scale flow-through steady-state multiple chamber system was designed and evaluated to estimate the NH emission potential of beef cattle manure. Four chambers constructed of two commercially available plastic containers (76 L) were interfaced with a multiplexer and FTIR gas analyzer. The chamber system was operated in a controlled environment room at 20°C with a fresh air exchange rate designed to prevent build-up of excessive gases. Fans on the inflow and exhaust ports of the chambers were matched to minimize pressure differences and resulted in an air flow velocity of 82 L/min. The air sample from each chamber was drawn through a 1-L volume filter (~30°C) and interconnecting tubing lined with heating wire to prevent condensation of gases. Emissions were measured sequentially at 5 min intervals (2 min flush, average of 3 readings at 1 min apart) from the four chambers, the background air within the room, and an N reference gas (zero calibration). Recovery was determined following the release of increasing concentrations of NH into each chamber on 3 different dates. Regression of measured vs. known NH concentration was = 1.1075 (± 0.0121) - 0.0758 (± 0.0304), r = 0.994. Feces and urine were combined in equal amounts to form manure (2 kg wet weight), placed in small trays within the chambers and incubated for 96 and 240 h. The NH -N emissions averaged 35.9 ± 1.20% of manure N and 54.5 ± 2.05% of urea-N at 96 h and increased to 63.5 ± 2.62% of manure N and 92.2 ± 3.78% of urea-N at 240 h. Measurement of emissions using the multiple flux chamber system were quantitative and reproducible indicating that the method is suitable for assessing the relative effectiveness of dietary strategies for beef cattle on the NH emission potential of manure.