Field-scale management and environmental drivers of N2O emissions from pasture-based dairy systems

• Published in: Nutrient cycling in agroecosystems Vol. 117; no. 3; pp. 299 - 315
• Main Authors: De Rosa, Daniele, Rowlings, David W., Fulkerson, Bill, Scheer, Clemens, Friedl, Johannes, Labadz, Martin, Grace, Peter R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-07-2020; Springer Nature B.V
• Subjects: Agriculture; Biomedical and Life Sciences; Carbon dioxide; Dairy farming; Dairy farms; Deposition; Emissions; Environmental management; Farms; Fluxes; Grazing; Grazing intensity; Greenhouse gases; Herbivores; Life Sciences; Milk; Nitrates; Nitrous oxide; Original Article; Pasture; Rainfall; Soil compaction; Soils; Spatial distribution; Generalised additive models; Spatial variability; Nitrous oxide; Grazing systems; Temporal variability; Greenhouse gases
• ISSN: 1385-1314; 1573-0867
• DOI: 10.1007/s10705-020-10069-7

Emissions of N
2
O from two dairy farms with different grazing intensity responded non-linearly to increasing soil nitrate availability and total rainfall. Higher N
2
O emissions were observed immediately after grazing, due to the possible increased incidence of N deposition from animal excreta, increased soil compaction and low plant N uptake. The spatial distribution of N
2
O fluxes and soil nitrate contents reflected the effect of animal treading and excreta N deposition with N
2
O fluxes in the proximity of field gateways 11 times higher than the field average. Three years average annual N
2
O emissions were 6 times higher (9.3 ± 2.6 kg N
2
O-N ha
−1
y
−1
) in the high grazing intensity farm than in the low grazing intensity farm (1.6 ± 0.2 kg N
2
O-N ha
−1
y
−1
). This corresponded to 2% and 0.9% of the fertiliser N inputs lost as N
2
O for the high and low intensity farm, respectively. The GHG intensity (N
2
O emitted per kg of fat and protein corrected milk FPCM) for the intensive system was only almost two times higher than the non-intensive system (0.12 vs 0.08 kg CO
2
-eq per kg FPCM y
−1
for the high and low intensity system, respectively). The high occurrence of N load hotspots near animal gateways in this study underlines the necessity to account for the spatial N variation in dairy grazing systems. Integrating the spatial management of N loads into improved farming practice has therefore significant scope to reduce N
2
O emissions and N losses from dairy grazing systems.