Nitrous oxide emissions from grazed grassland

Abstract

Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N 2 O budget. This paper summarizes relevant literature data on N 2 O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N 2 O budget. The effects of grazing animals on N 2 O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N 2 O. There are no pertinent data about the effects of compaction by treading cattle on N 2 O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown‐only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N 2 O‐N per year. This is slightly more than 10% of the global budget.