Quantifying contaminant losses to water from pastoral land uses in New Zealand III. What could be achieved by 2035?

Abstract

To meet the water quality outcomes sought by catchment communities and regulators, the losses of nitrogen (N), phosphorus (P) and sediment from dairy and sheep/beef farms must be reduced across many catchments. We conducted a high-level desktop analysis of farm typologies and established that if mitigation actions were fully implemented across dairy and sheep/beef farms, losses of N and P could have been decreased by up to 16 and 23%, respectively, compared to the estimated losses for 2015 (where established actions were only partially implemented). Potential decreases were greater for dairy land (34% N and 26% P) because of its greater per hectare yield and number of mitigation actions available before land use change is required. If established and developing mitigation actions were fully implemented by 2035, potential N, P and sediment losses may decrease by up to 34, 39 and 66%, respectively, compared to actual 2015 losses. These results can inform investment and planning by the rural sector as part of an assessment of the potential for on-farm actions to mitigate losses from existing land use.