Evaluation of two potential on-farm measures for reducing greenhouse gas emissions from an average dairy farm on the West Coast of the South Island of New Zealand

Abstract

Agriculture contributes about 60% of New Zealand's total greenhouse gas emissions. Management practices for reducing these emissions will be required to meet our future international commitments. This paper presents estimates of two practical on-farm measures for reducing total greenhouse gas emissions from an average dairy farm on the West Coast of the South Island of New Zealand: 1) the incorporation of cereal silage into the diet, and 2) the strategic use of a stand-off pad in winter. Total calculated greenhouse gas emissions were reduced by about 14% if fertiliser N-boosted pasture was replaced with bought-in cereal silage grown off-farm. The estimated reduction in emissions was due to reductions in nitrous oxide and carbon dioxide emissions, whereas methane emissions were not significantly affected by this management practice. Reduced methane emissions required an increase in per animal production and a corresponding decrease in stocking rate. The use of a stand-off pad during winter did not significantly affect total greenhouse gas emissions using current inventory calculations. However, recent research suggests that it may reduce emissions by 3 to 8%, when accounting for the seasonal variation in N2O emissions and reduced fertiliser N requirements due to reduced pasture damage. A preliminary assessment of the economic implications of the cereal silage option suggested the cost of using cereal silage is likely to be higher than any savings that could be accrued from carbon credits obtained from reducing greenhouse gas emissions. However, the costs associated with building and using a stand-off pad are likely to be off-set against a potential increase in pasture production, and carbon credits obtained from a reduction in greenhouse gas emission would represent a net cost saving. Keywords: carbon dioxide, cereal silage, dairying, methane, mitigation options, nitrous oxide, stand-off pad