New research shows a plantain pasture mix reduces nitrate leaching from dairy farms (whāma kau) by as much as 60%, in part by diluting cows’ urine.
There was no difference in milk production between the plantain and control pastures in the trial.
The results come from the DairyNZ-led Plantain Potency and Practice (PPP) programme, using PPG Wrightson Seeds’ Ecotain plantain.
Farm trials at Massey University and initial results from a trial at Lincoln University are showing similar trends.
Massey University Professor Emeritus Peter Kemp and his team have been researching the effects of plantain over several years and the experimental plots were established at the university in 2019.
“Each one has an individual tile drain system underneath it and all the drainage water from the individual paddock is piped down to the tipping buckets where we measure the total drainage water from each paddock, and we sub-sample it to measure the nitrogen concentration in the water,” Kemp said.
The researchers also measured nitrogen in the cows’ urine, dung and plasma.
The cows take on the same amount of nitrogen from the plantain mix pasture, but it is allocated differently from ryegrass, Kemp said.
“When they’re eating Ecotain, there’s a greater allocation of nitrogen to dung versus urine than when they’re in a ryegrass pasture.”
That means that in total there’s less nitrogen reaching the pasture from urine and that nitrogen has a better chance of being reabsorbed by the pasture.
In addition, plantain increases the volume of urine, diluting it and also spreading it out across the paddock.
“There is less nitrogen available for leaching as you go into autumn and winter.”
Initial results from the programme’s Lincoln University study in Canterbury, on lighter soils under irrigation, show similar trends to the Massey University trial’s 20-60% reduction, with a 38-50% reduction in nitrogen leaching from pasture containing 24% Ecotain plantain. More data is being collected to confirm these results.
Significantly, Massey University research has shown that this pasture regime also decreases the greenhouse gas emissions (nga tukunga hau kati) of nitrous oxide, a key issue for climate change, Kemp said.
He said the Massey trial site allows the results to be directly transferable to current farming systems in New Zealand.
DairyNZ chief executive Dr Tim Mackle said these are exciting results.
“We now have robust scientific evidence that Ecotain plantain is an effective solution to help dairy farmers further reduce farm footprint and continue playing their part in improving water quality,” he said.
“Plantain can bring significant benefits to local waterways and communities – we all want healthy freshwater to swim and play in, and dairy farmers can confidently use Ecotain plantain on farm to support that.”
PGG Wrightson Seeds chief executive John McKenzie said he is pleased with the results, which “support current initiatives to protect our natural environment and improve waterways”.
The $22 million seven-year PPP programme is funded by DairyNZ, by the government through the Ministry for Primary Industries’ Sustainable Food & Fibre Futures fund, PGG Wrightson Seeds and Fonterra, working with six additional research and delivery partners.
The research programme also includes more than 20 partner farms, where plantain is being introduced and leaching is monitored.