Thursday, July 7, 2022

New tool helps cut nutrient loss

A farmer can collect all the data in the world but it’s deciding what it means and how to implement it that can be the difference between progress and treading water.

One Central Hawke’s Bay farmer has been letting a new decision-support tool crunch the numbers and now has a clear strategy to mitigate nutrient loss on his farm.

MitAgator was the product of a Primary Growth Partnership involving the Ministry for Primary Industries and Ballance Agri-Nutrients. It was developed by AgResearch.

It took raw nutrient data and turned it into onfarm outcomes.

Ballance farm sustainability services specialist North Island team leader Christina Finlayson has been trialling the tool with Miles McBain, who farms the 300ha Kahotea in the Papanui sub-catchment of the Tukituki River.

The mixed cropping and stock fattening farm was in an area known for high levels of dissolved phosphorus concentrations and was a priority for the Hawke’s Bay Regional Council.

Finlayson, who was using the project to complete her master’s degree, said the process started with a nutrient budget produced in Overseer.

“Then we work with the mapping team at Ballance and they develop the map and work in all the GIS layers.”

The nutrient budget and the farm map package were then entered into MitAgator.

“We push the button and it develops the different risk maps.”

From there Finlayson went back to the farm and worked with the farmer to establish where his or her hotspots were, based on the different contaminants that were important in particular catchments.

“We prioritise what contaminant we’re really going to focus on reducing,” she said.

“Then we work through the different mitigations by running different various scenarios that quantify the reductions to optimise the best place to put, say, a sediment trap.”

The key was practicality.

“Before recommending a mitigation we need to go onfarm to make sure it is practical.

“We’re making sure that while you’re spending all this money on making an environmental improvement it will have the biggest bang for your buck.”

McBain said it had been a simple process to go through.

“I think it’s a really positive thing. Moving forward we’re going to implement some of the ideas that Christina has come up with to improve things on the land.

“There’s all sorts of new ideas and things to do that are pretty exciting.”

McBain knew his farm and his catchment and was committed to make gains in terms of nutrient management.

“It’s really important. I just hope everybody else around us does the same thing so it all comes together. It’s a community thing.”

MitAgator forecast he could make a 36% reduction in phosphorus runoff at the farm.

The model also showed 75% of the sediment lost from the farm was from 5-10% of its area.

MIles’ wife Megan is a landscape architect and was planning on planting trees and other plants around the farm –  now she can use the sediment risk map as a planting guide to minimise sediment losses.

Finlayson said the regional council had been very supportive of the tool’s use.

McBain was totally on board as well.

“It’s a new system but it seems to have worked really well and done everything we hoped it would. And it’s only going to get easier.”

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