Ammonia emissions from cattle urine and dung excreted on pasture

[摘要] Twelve cattle were kept for three days in a circular area of 16 m radius onshort pasture and fed with freshly-cut pasture. Ammonia (NH₃) emissionsfrom the urine and dung excreted by the cattle were measured with amicrometeorological mass-balance method, during the cattle presence and for10 subsequent days. Daily-integrated emission rates peaked on Day 3 of theexperiment (last day of cattle presence) and declined steadily for five daysthereafter. Urine patches were the dominant sources for these emissions. OnDay 9, a secondary emissions peak occurred, with dung pats likely to be themain sources. This interpretation is based on simultaneous observations ofthe pH evolution in urine patches and dung pats created next to the circularplot. Feed and dung samples were analysed to estimate the amounts ofnitrogen (N) ingested and excreted. Total N volatilised as NH₃ was19.8 (± 0.9)% of N intake and 22.4 (± 1.3)% of Nexcreted. The bimodal shape of the emissions time series allowed to inferseparate estimates for volatilisation from urine and dung, respectively,with the result that urine accounted for 88.6 (± 2.6)% of thetotal NH₃ emissions. The emissions from urine represented 25.5 (± 2.0)% of the excreted urine-N, while the emissions from dung amounted to11.6 (± 2.7)% of the deposited dung-N. Emissions from dung mayhave continued after Day 13 but were not resolved by the measurementtechnique. A simple resistance model shows that the magnitude of theemissions from dung is controlled by the resistance of the dung crust.

[学科分类] 地球化学与岩石