Farming without N fertiliser? Local trial results

The final field day for the Collective’s Sustainable Farming Fund (SFF) project was held at Parekarangi Trust Farm on Tuesday 3 March.The forty attendees, including dairy farmers and rural professionals, heard from Stewart Ledgard (AgResearch soil scientist) on the latest results from the 3-year nitrogen fertiliser trial.

These field trials assess the effects of standard, “strategic” (low) and nil N fertiliser use on dairy farms. Stewart Ledgard acknowledged that while there has been a large amount of research into the effects of nitrogen on freshwater “there is much less science to help inform farmers about reducing nitrogen inputs and the long term impacts of this on pasture and the wider farm system”.

The latest results indicate that while the strategic and nil N fertiliser plots grew less dry matter, the pasture quality was similar to the standard fertiliser plots, with little indication yet of reversion to low productivity grasses in the strategic and nil N treatments. The separate “farm system” trial at Parekarangi directly measures N leaching under a standard and nil N fertiliser system. This showed a five-fold reduction in N leaching in 2013, and a more typical halving of N leaching in 2014 for the nil N system which also grew 16-17% less dry matter. The high N leaching variation between years was probably due to the effects of the 2013 drought and the timing of an autumn fertiliser application when a large amount of rain and soil drainage occurred. To find out more, you can view a recent presentation given at Massey University below.

The SFF project – ‘Meeting nutrient loss targets on dairy farms in the Lake Rotorua catchment’ started in July 2011. It was due to finish in June 2014 but was extended to March 2015 with additional support from MPI, BOPRC, DairyNZ and Ballance Agri-Nutrients. The field trials will continue until December 2015, thanks to further BOPRC and DairyNZ funding.