Effects of irrigating dairy-grazed grassland with farm dairy effluent on nitrous oxide emissions
Date
2008
Authors
Luo, J.
Saggar, S.
Bhandral, R.
Bolan, N.
Ledgard, S.
Lindsey, S.
Sun, W.
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Plant and Soil, 2008; 309(1/2):119-130
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Abstract
While irrigation of farm dairy effluent (FDE) to land is becoming popular in New Zealand, it can lead to increased emissions of the greenhouse gas nitrous oxide (N<inf>2</inf>O). This paper reports the results from trials on N <inf>2</inf>O emissions from irrigation of FDE to two dairy-grazed pastures on two poorly drained silt-loam soils located at Waikato and Manawatu, New Zealand. These pasture soils were periodically irrigated with FDE under contrasting soil moisture conditions with water-filled pore-space (WFPS) ranging between 26% and 94%. Nitrous oxide emissions were measured from the FDE irrigated and unirrigated sites using large numbers of static chambers (12-20). Irrigation of FDE generally increased N<inf>2</inf>O emissions compared to the control. N <inf>2</inf>O emissions varied with changes in climatic conditions and soil WFPS. Overall N<inf>2</inf>O emissions from effluent-derived N ranged between 0.01% and 4.93% depending on irrigation time and soil WFPS. Lower N<inf>2</inf>O emissions from FDE were attributable to very low soil WFPS conditions during the dry seasons. Higher N<inf>2</inf>O emissions were measured from application of FDE to a recently grazed pasture on wet soil. Our results suggest strategic application of FDE during dry summer and autumn seasons can reduce N <inf>2</inf>O emissions from application of FDE. Delaying effluent-irrigation after grazing events could further reduce N<inf>2</inf>O emissions by reducing the levels of surplus mineral-N. © 2008 Springer Science+Business Media B.V.
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