stuff.co.nz, 31 May 2017

It’s hard for farmers to turn a profit at the best of times, let alone while reducing their nitrogen footprint. But a study by Landcare Research has found farmers can achieve both. Caroline King reports.

Landcare Research has proven the age-old farming practice of growing lucerne can help farmers like Mike and Sharon Barton meet water quality compliance rules previously viewed as a handbrake on their business.

The Bartons’ farm is near Lake Taupo. Due to concerns about the health of the lake, the Waikato Regional Council set nitrogen discharge caps on farms in the Taupo catchment.

The Lake Taupo Protection Trust also brought about a permanent change in land use, including conversion to forestry, to reduce the amount of nitrogen entering the lake by 20 per cent (approximately 170 tonnes).

Installing lysimeters on Mike and Sharon Barton’s Taupo farm.

However, the trust has also turned to science to find long-term ways farmers can reduce their nitrogen footprint. Findings from a five-year-study by Landcare Research have shown the answer was right under everyone’s noses – cut and carry lucerne.

Dr Malcolm McLeod, a soil scientist at Landcare Research, found nitrogen leaching from cut and carry lucerne – where the leafy high-protein forage is harvested and baled into hay or silage – is 5kg a hectare a year. This is significantly less than the 19kg a hectare a year set by the Waikato Regional Council and than previous estimates of up to 26kg.

“The actual leaching is quite low. It’s very similar to cut and carry pasture,” McLeod says.

This gives farmers a lot more leeway as they may only have a discharge allowance between 12 and 20kg of nitrogen a hectare a year.

Each farm has a different nitrogen discharge allowance. A farm’s NDA was determined by the year it had the highest leaching during the benchmark period of July 2001 and June 2005.

He says the findings are great news for farmers.

“Costs are going up for farmers and the nitrogen cap limits how much production they can do, but lucerne provides a potential alternative. Now they know how much it’s leaching they can put in quite big areas and increase production,”  McLeod says.

The finding has been passed on to the Overseer committee.

“It’s another tool in the tool box to try and keep the lake in good condition,” he says.

Another added benefit for the lake is that lucerne uses nitrogen from the air so does not require any nitrogen fertiliser.

The data for the study was collected from 12 barrel lysimeters installed on the Bartons’ 142-hectare beef farm in Tihoi.

Mike Barton says they supported the research because up until that point nothing had shown how farmers operating under a nitrogen cap could increase their stocking rate or profitability.

The research is the “first significant win” for farmers, he says.

“It’s probably the first real breakthrough we’ve had in the nitrate issue since this process began back in 2000.”

It provides hope for farmers who have been struggling for some time.

“The real price for food producers has gone down over the last 60 years. Our response has been to increase our carrying capacity – increasing production per hectare – but nitrogen caps denied farmers the ability to intensify.”

Cut and carry lucerne provides an economically viable alternative and some farmers are already taking it, Mike says.

“Quite a few dairy farmers outside the Taupo catchment, aware of the research, have brought land in the catchment and are growing lucerne and exporting it outside the catchment.”

“That land was also less expensive land so it made it worthwhile from a financial point of view for farmers outside to buy it but still be able to use it and transport it out,” Sharon says.

Mike says lucerne allows farmers to double their dry-matter production without increasing nitrogen leaching.

“Control lysimeters are growing between 9000 and 10,000kg of dry matter in a year. The lucerne is growing 20 to 25 tonnes of dry matter, so more than twice what the grass is growing and we’re leaching the same. That gives you a clue of how important it is.

“If I can grow twice as much dry matter and still stay within my leaching limit that allows me to either finish cattle more quickly or finish them to higher weights. Either way it’s a win for us.”

Mike says the research is of value to farmers across the country as other regions, including Canterbury and the Manawatu, have followed suit setting nitrogen discharge caps.

“This sort of research can have application on any other free-draining soils. It’s been carried out on pumice soils but there is a crossover, so any other catchments facing similar nutrient capping challenges this research has application for them.”

Lake Taupo Protection Trust chairman Clayton Stent agrees.

“That lucerne research is relevant to any farmer across New Zealand. Any gains that can be made in certainty, which this particular research has done, assists our local farmers but that research is available to any farmer when it comes to nitrogen discussions. It’s a very valuable piece of research not just locally, it will have national recognition.”

While the research is of help to farmers struggling with nitrogen discharge caps the key benefit is to Lake Taupo, Stent says.

“The obvious benefits of the project are the health of the lake, which was the whole driver for this. Ultimately, what it’s about is stopping the nitrogen growing plants in the lake which choke it.”

And it’s already appearing to work.

“It’s a 30 to 40 year outcome before we know truly whether it’s worked, but initial response from the science is that it has started working, there’s been a bit of an arresting.”

He says the project proves how a huge challenge could be overcome by the community coming together and working collaboratively.

The next stage of the project will look at what impact urinary nitrogen from livestock grazing on lucerne pastures has on nitrogen leaching.

Work will soon begin installing new lysimeters on the Bartons’ property. Urine patches will be used to simulate the areas being grazed. This next phase will run for four to five years.

Mike Barton says if the findings are the same as the cut and carry project it will be a “huge breakthrough”.