ABSTRACT

In New Zealand the primary sector together with central and local government agencies have been promoting measures to mitigate the adverse effect of farming practices on water quality over the last few decades. We assessed the effectiveness of some key measures such as stock exclusion, riparian protection, and nutrient and effluent management on reducing losses of nitrogen (N), phosphorus (P) and sediment to water. Our aim was to determine how much progress has been made in decreasing contaminant discharges between 1995 and 2015 and to determine what the loads would have been if no mitigation had occurred. To do this we estimated losses from 37 dairy and non-dairy/sheep/beef farm typologies that captured the main attributes of production and contaminant loss pathways, nationally. We also accounted for the rate of uptake of measures. Our findings indicated that while the implementation of these measures has helped to reduce P losses (an estimated 20%–25% reduction) to water, they have not been sufficient to off-set estimated increases in N losses (25%) due to expansion of dairy land over the same period. National sediment load is estimated to have decreased (29%) because of afforestation and other soil conservation works.

摘要

在新西兰，初级部门与中央和地方政府机构在过去几十年中一直在推动采取措施，以减轻农业实践对水质的不利影响。我们评估了一些关键措施的有效性，如种群排除、河岸保护以及营养和废水管理，以减少氮 (N)、磷 (P) 和沉积物向水中的损失。我们的目标是确定 1995 年至 2015 年间在减少污染物排放方面取得了多大进展，并确定如果没有采取任何缓解措施，负载会是多少。为此，我们估计了 37 个乳制品和非乳制品/绵羊/牛肉农场类型的损失，这些类型捕获了全国范围内生产和污染物损失途径的主要属性。我们还考虑了采取措施的速度。我们的研究结果表明，虽然这些措施的实施有助于减少水的 P 损失（估计减少 20%–25%），但它们还不足以抵消由于扩张导致的 N 损失估计增加（25%）同期的奶牛土地。由于植树造林和其他水土保持工程，全国泥沙负荷估计已经减少（29%）。