Improved nitrous oxide emission factors for cattle and sheep excreta deposited in New Zealand hill country

Jiafa Luo1, Coby Hoogendoorn2, Tony van der Weerden3, Surinder Saggar4, Cecile de Klein3, Donna Giltrap4

1 AgResearch Ruakura, 10 Bisley Road, Hamilton 3240, New Zealand. Email: [email protected]

2 AgResearch Grasslands, Tennent Drive, Palmerston North 4442, New Zealand

3 AgResearch Invermay, Puddle Alley, Mosgiel 9053, New Zealand

4 Landcare Research, Riddet Road, Massey University, Palmerston North 4442, New Zealand

Abstract

Animal grazing behaviour in hill country results in lower inputs of animal excreta on steep slopes (> 25o) and greater nitrogen (N) deficiency compared to medium slopes (12 - 25o). Nitrous oxide (N2O) emission factors from excreta (EF3; percentage of deposited animal excreta-N emitted as N2O, %) may differ with slope. A field study was conducted in four regions of New Zealand to determine the effect of slope on the autumn-winter N2O EF3 from animal urine and dung. EF3 values at all the sites were generally very low, with most of the averages being less than 0.1%, and highly variable. The EF3 from sheep urine was significantly higher on the medium slope than on the steep slope. EF3 values for beef cattle dung tended to be higher than for sheep dung on both slope classes. There was a tendency (non-significant) for higher EF3 values for sheep dung, and higher beef cattle urine and dung, on the medium slopes than on the steep slopes.