Journal Article

Effects of bovine urine, plants and temperature on N sub(2)O and CO sub(2) emissions from a sub-tropical soil

Uchida, Yoshitaka, Kelliher, Francis M, Clough, Timothy J, Sherlock, Robert R, Hunt, John E

2011

Overview

Grazing ruminants urinate and deposit N onto pastoral soils at rates up to 1,000 kg ha super(-1), with most of this deposited N present as urea. In urine patches, nitrous oxide (N sub(2)O) emissions can increase markedly. Soil derived CO sub(2) fluxes can also increase due to priming effects.While N sub(2)O fluxes are affected by temperature, no studies have examined the interaction of pasture plants, urine and temperature on N sub(2)O fluxes and the associated CO sub(2) fluxes. We postulated the response of N sub(2)O emissions to bovine urine application would be affected by plants and temperature. Dairy cattle urine was collected, labelled with super(15)N, and applied at 590 kg N ha super(-1) to a sub-tropical soil,with and without pasture plants at 11 degree , 19 degree , and 23 degree C. Over the experimental period (28 days), 0.2% (11 degree C with plants) to 2.2% (23 degree C with plants) of the applied N was emitted as N sub(2)O. At 11 degree C, plants had no effect on cumulative N sub(2)O-N fluxes, whereas at 23 degree C, the presence of plants significantly increased the flux, suggesting plant-derived C supply affected the N sub(2)O producing microbes. In contrast, a significant urine application effect on the cumulative CO sub(2) flux was not affected by varying temperature from 11-23 degree C or by growing plants in the soil. This study has shown that plants and their responses to temperature affect N sub(2)O emissions from ruminant urine deposition. The results have significant implications for forecasting and understanding the effect of elevated soil temperatures on N sub(2)O emissions and CO sub(2) fluxes from grazed pasture systems.

• Subject: Ruminantia