NZ Farmer - Search on for forages that reduce nitrogen leaching

The Forages for Reduced Nitrate Leaching project is delivering better than expected results, says programme leader Ina Pinxterhuis. She talked to Tony Benny.

With public concern over the effect of dairy farming on the environment mounting, DairyNZ has taken the lead in finding ways to reduce farming's negative effects while maintaining productivity and profitability.

Forages for Reduced Nitrate Leaching is an MBIE-funded collaborative programme by DairyNZ, AgResearch, Plant and Food Research, Lincoln University, Foundation for Arable Research and Landcare Research with the aim of cutting nitrate leaching losses by 20 per cent.

It combines field and animal experiments with computer modelling and trials on nine Canterbury monitor farms – four dairy, two sheep and beef, two arable and one mixed arable/dairy.

"I think for New Zealand it is very new to have farmers in a research programme right from the beginning but from my experience in the Netherlands, I've learnt that is actually really useful," says programme leader Ina Pinxterhuis.

"They provide feedback, they give you ideas, they have tested things already that you've never heard about and they help us decide what sort of research is needed, which questions need answering and which treatments we put in the experiments."

Farmers can also tell the research scientists whether they think their ideas are practical and if they're actually likely to be put into practice on-farm.

"We didn't want to push the boat out too far because we know farmers really do need things now. We can't go and work on things that aren't ready to be used for the next 10 years, they really have to make changes now so we wanted to stay quite close to current practice."

Pinxterhuis also worked on the Matrix of Good Management project which informed industry-agreed good management practices for each sector, on which farm environment plans (including a variety of templates) are now based.

New nutrient limits are already in place in Canterbury and regulations will tighten in coming years, with farmers in some areas deemed "red zones" because of degraded water quality having to reduce N-losses by 30 per cent over the next few years.

In an earlier research project, Pastoral 21, DairyNZ and other research partners ran trials on farmlets in Waikato, Manawatu, Lincoln (Canterbury) and Telford (South Otago) and found that by reducing inputs and using very high breeding value cows, they could reduce leaching by 40 per cent, albeit with a 5 per cent reduction in profit (depending on the payout).

"That really showed there is an opportunity but the reduction in profit was still there. We were looking for other options that would increase production and profit as well," says Pinxterhuis.

That research also raised questions about the role of different forages in reducing leaching and to answer those, FRNL was launched in 2013.

"We developed a very large programme that would look at alternative pasture species and crops with a low nitrogen content so that we could reduce the amount of nitrogen going into the cow.

"The biggest problem from grazing animals is that they eat material with lots of nitrogen, they don't utilise it all and the excess ends up in the urine patch and the urine patch has a high concentration but a small area so we lose a lot from there."

FRNL has intensively studied plantain which had been shown to reduce nitrogen in urine. Plantain also has a dilution effect on cows' urine and has recently been shown to reduce nitrate loss from soil.

But while its benefits are evident, getting plantain to persist in pasture swards after the first two years is proving challenging. Trial work suggests it needs to comprise 25 to 30 per cent of a cows' diet to have a significant benefit, but this is being investigated further.

"At the moment we think you can just drill it into existing pastures so we started a couple of experiments last year and also on the monitor farms, introducing it in different ways and we're following that through," Pinxterhuis says.

"We don't want to have to resow pastures very often because we lose a lot of nitrogen in that process as well because there is a lot of nitrogen in the stubble and the roots and when it's ploughed it all gets broken down, it mineralises and then you have a whole lot of nitrogen sitting in the soil which can be lost."

Fodder beet is another weapon being studied. It contains low amounts of nitrogen and hence there's less nitrogen in the urine hitting the ground. But there is concern over whether too much fodder beet in the cows' diet could lead to animal health issues.

The third measure being investigated is growing catch crops following grazed crops to take up soil nitrogen.

"A catch crop like oats or winter triticale can grow quickly in low temperatures so even in the winter it will start to take up nitrogen. It utilises water so drainage is less, so it already has a benefit in reducing leaching really early on but then you also have to think about what happens once you've grown it. If you're letting it grow for whole crop silage, it's December – can you still get pasture in after that?"

The scientists are working on those questions now. They're using the results they've collected so far to modify farm system computer models so they can test different scenarios at farm system level.

Pinxterhuis says adding plantain to pasture mixes, growing fodder beet and catch crops all help reduce nitrate leaching without adversely affecting production and profitability, though there's still work to be done to perfect the system.

"It's been a really amazing journey, this programme. We've really made some tracks.

"With plantain we've learned a lot more about the mechanisms and the benefits seem actually much bigger than we ever envisaged. With catch crops and fodder beet, we knew the processes for how it would work but how much it would actually help us, we did not know and that also seems better than what we actually expected."