DairyNZ project leader Virginia Serra says the limits are challenging but the sector is committed to helping farmers achieve them while maintaining resilient businesses.
"This project builds on previous nitrogen loss research. It aims to give farmers confidence the limits are achievable," she says. "Many have been making changes to reduce nitrogen loss for some time and this will continue to build on that."
The project was launched at A Farm Systems of the Future field day on a Canterbury dairy farm on December 5. The event explored the host farmer's high performance and lower footprint and how other farmers are adjusting their systems to reduce footprint profitably.
The project will initially involve a few partner farms making changes to reduce nitrogen loss and tracking the impact. But Serra says DairyNZ is also looking for other Hinds and Selwyn farmers and rural professionals to be involved: "Over two years, we hope to be working alongside 50 partner farms, where we can monitor the success of changes to reduce nitrogen loss."
Canterbury farmer Campbell Tait is one of a group of farmers involved in the Meeting a Sustainable Future project and says DairyNZ modelling provided invaluable information to reduce nitrogen loss on his farm – 400 hectares at Ashburton, with 800 milking cows and 300 beef calves.
"It showed us where we could get the biggest impact, sometimes by making relatively small changes," he says.
Recommendations included smarter decision-making around winter and spring cropping, optimising soil fertility, reducing nitrogen fertiliser use on all areas and improving irrigation infrastructure and effectiveness.
Campbell has considered many of these things before, but the modelling showed where the biggest gains were. More than 30 different management zones were identified in the 2016/17 season and understanding how different variables affect nitrogen loss is fundamental.
"Variability in soil fertility is highly evident on our property," says Campbell. "We have grid soil tested down to one-hectare parcels and now use variable rate spreading to correct phosphate and potassium deficiencies within paddocks."
"This makes for immediate gains in productivity and savings where fertiliser is not required. However, it also enables better use of the nitrogen fertiliser applied, as pasture performance is not being constrained by another mineral deficiency."
Another key change has been to eliminate nitrogen use on spring cereal crops (following winter feed).
"I had always been advised to apply additional nitrogen to ensure the yield was maximised. Now we are focused on minimising loss of nitrogen and the spring cereal is solely to soak up the surplus."
Some other suggestions are a bit harder financially, he says, including investment in a feed pad and upgrading irrigation from travelling guns to centre pivots.
Campbell says reducing nitrogen leaching by 15 per cent by 2025 is achievable while the 36 per cent target by 2035 will be the most challenging.
"We'll have to use a lot of tools to make that happen, and most of all, a sound balance sheet. If we reduce nitrogen fertiliser use from 240kg/ha to 170kg/ha, I'd expect to increase supplementary feed use or reduce our stocking rate – there's surely a trade-off."
The Canterbury Dairy Leaders Group, which aims to ensure a viable and enduring dairy sector in the region, supports the initiative, with chairman Alister Body saying the project will provide leadership for all farmers on one of the biggest challenges they face.
"This work is a great way for Selwyn and Hinds dairy farmers, along with others nationally, to watch and learn about the best options to reduce nitrogen losses and meet the future goals," says Body. "It will be very interesting to follow."
