The mission

The Best Practice Dairy Catchments project ran from 2001-2010 in five small dairy-dominated catchments. It drew on the latest science to provide farmers with advice and helped them develop farm plans with mitigation strategies to reduce contaminant loss.

The project continued to monitor water quality and carry out farmer practice surveys from 2011 to 2021 to provide long-term data collection. This allowed water quality trends to be assessed over a 20-year period to see how on-farm practice change affected water quality.

Key learning

Over the full 20-year monitoring period, two-thirds of in-stream water quality trends were improving, but several were degrading, especially nitrate-nitrogen.

What this research means for you

Analysis of this globally unique, long-term dataset has helped show how extension advice can support you to implement good farming practices and improve water quality. It has also shown that detecting water quality improvements takes time and long-term monitoring.

What we've learned

These improvements were attributed to farmers actioning good farming practices around effluent management, wintering, and shifting from flood to spray irrigation. As part of the Dairy Clean Streams Accord, farmers also excluded stock from waterways and undertook riparian planting which will have also decreased contaminant concentrations.

Good farming practices have decreased ammonia-nitrogen, phosphorus and suspended sediment concentrations in waterways in project catchments. However, an increase in nitrate-nitrogen concentrations was caused by transitioning from flood to spray irrigation in Waikakahi, and an increase in stocking rates and nitrogen fertiliser use. Despite gains in catchments using good farming practices, there’s room for further improvement.

How are farmers involved?

Farmers were involved in actioning practice changes on farm. They also attended field days and workshops, and provided information on their on-farm actions through regular farm practice surveys.