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Animals 2018, 8(12), 234;

The Effects of System Changes in Grazed Dairy Farmlet Trials on Greenhouse Gas Emissions

AgResearch, Invermay Agricultural Centre, Mosgiel 9053, New Zealand
DairyNZ Ltd., Private Bag 3221, Hamilton 3240, New Zealand
AgResearch, Grasslands Research Centre, Palmerston North 4410, New Zealand
DairyNZ Ltd., Canterbury Agricultural & Science Centre, Lincoln 7608, New Zealand
AgResearch, Lincoln Research Centre, Lincoln 7674, New Zealand
Present Address: School of Agriculture and Environment, College of Sciences, Massey University, Palmerston North 4442, New Zealand.
Present Address: DuPont Industrial Biosciences, 2300 AE Leiden, The Netherlands.
Author to whom correspondence should be addressed.
Received: 15 October 2018 / Revised: 15 November 2018 / Accepted: 4 December 2018 / Published: 7 December 2018
Full-Text   |   PDF [1186 KB, uploaded 7 December 2018]   |  

Simple Summary

Dairy farm system practices aimed at reducing nitrate leaching can also reduce emissions of the greenhouse gases methane and nitrous oxide. A study comparing ‘current’ and ‘improved’ grazed dairy system practices showed that ‘improved’ systems generally produced lower greenhouse gas emissions while milk production was maintained. The amount of feed eaten per hectare was the key driver of total greenhouse gas emissions per area, with ‘improved’ systems generally exhibiting lower total enteric methane and less N flowing through the herd.


An important challenge facing the New Zealand (NZ) dairy industry is development of production systems that can maintain or increase production and profitability, while reducing impacts on receiving environments including water and air. Using research ‘farmlets’ in Waikato, Canterbury, and Otago (32–200 animals per herd), we assessed if system changes aimed at reducing nitrate leaching can also reduce total greenhouse gas (GHG) emissions (methane and nitrous oxide) and emissions intensity (kg GHG per unit of product) by comparing current and potential ‘improved’ dairy systems. Annual average GHG emissions for each system were estimated for three or four years using calculations based on the New Zealand Agricultural Inventory Methodology, but included key farmlet-specific emission factors determined from regional experiments. Total annual GHG footprints ranged between 10,800 kg and 20,600 kg CO2e/ha, with emissions strongly related to the amount of feed eaten. Methane (CH4) represented 75% to 84% of the total GHG footprint across all modelled systems, with enteric CH4 from lactating cows grazing pasture being the major source. Excreta deposition onto paddocks was the largest source of nitrous oxide (N2O) emissions, representing 7–12% of the total GHG footprint for all systems. When total emissions were represented on an intensity basis, ‘improved’ systems are predicted to generally result in lower emissions intensity. The ‘improved’ systems had lower GHG footprints than the ‘current’ system, except for one of the ‘improved’ systems in Canterbury, which had a higher stocking rate. The lower feed supplies and associated lower stocking rates of the ‘improved’ systems were the key drivers of lower total GHG emissions in all three regions. ‘Improved’ systems designed to reduced N leaching generally also reduced GHG emissions. View Full-Text
Keywords: environmental modelling; pasture systems; nitrous oxide; methane emissions; nitrate leaching environmental modelling; pasture systems; nitrous oxide; methane emissions; nitrate leaching

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van der Weerden, T.; Beukes, P.; de Klein, C.; Hutchinson, K.; Farrell, L.; Stormink, T.; Romera, A.; Dalley, D.; Monaghan, R.; Chapman, D.; Macdonald, K.; Dynes, R. The Effects of System Changes in Grazed Dairy Farmlet Trials on Greenhouse Gas Emissions. Animals 2018, 8, 234.

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