- Plantain cut nitrate leaching by 33% over four years with no reduction in milk or pasture production.
- Researchers say four-year study provides the clearest proof yet of plantain’s nitrate-cutting potential.
- DairyNZ says plantain may offer a lower-cost alternative to major cuts in fertiliser, feed or stocking rates.
Final results from DairyNZ’s Plantain Potency and Practice programme showed annual nitrate leaching fell by an average of 33% at Lincoln University Research Dairy Farm, declining from 18kg/ha/year to 12kg/ha/year in perennial ryegrass-white clover pastures containing Ecotain plantain.
The farmlet trial compared nitrogen losses and production performance between pastures sown with and without plantain.
Researchers found milk production, herbage production and silage use remained similar between treatments.
“The findings demonstrate that plantain can deliver environmental benefits without compromising farm performance,” said Kate Fransen, senior project manager at DairyNZ.
The results add to evidence generated through the programme’s grazing trial at Massey University, smaller component studies and the Low N Farmlet Trial at Lincoln University, which combines plantain with other nitrogen-mitigation strategies.
Results exceed expectations
Notably, the reductions recorded at Lincoln were more than double those predicted by current nutrient models, which primarily account for plantain’s ability to reduce urinary nitrogen excretion.
Fransen explained that plantain’s high water content dilutes cow urine, while its nutritional composition diverts more nitrogen into faeces and milk, and less into urine.
“We are now gaining a better understanding of the effects of plantain on drainage and nitrogen cycling in soil, which result in additional reductions in nitrogen leaching,” she said.
DairyNZ said it aims to have these additional effects incorporated into nutrient-management models such as Overseer by 2028.
The study also found that relatively low levels of plantain remained effective.
Although plantain content plateaued during the final years of the trial, nitrate-leaching reductions remained consistent.
“At the Lincoln site, we achieved consistent reductions in nitrate leaching over four years, despite plantain content plateauing to 10-15% in the final years of the trial,” said Fransen.
Practical adoption for farmers
Alongside the research programme, DairyNZ worked with more than 30 partner farmers in nitrogen-sensitive catchments to assess practical management approaches and wider farm-system impacts.
Plantain is a short-lived perennial that requires ongoing oversowing or undersowing to maintain pasture content.
Partner farmers were also able to sustain plantain levels of 10 to 15 per cent by including Ecotain in new pasture mixes and broadcasting seed annually, at an estimated cost of NZ$46/ha (US$26.97/ha) per year.
According to DairyNZ modelling, achieving similar reductions in nitrogen leaching without plantain would likely require substantial cuts to nitrogen fertiliser use, imported feed and stocking rates, or significant infrastructure investment, with greater impacts on farm profitability.
Climate potential
The benefits of plantain for nitrogen-loss reduction are already recognised in regulatory frameworks across Canterbury, Southland, Waikato, Bay of Plenty and Horizons regions.
Researchers are also investigating whether plantain can deliver additional climate benefits.
Studies from New Zealand and Ireland indicate the forage may help reduce methane and nitrous oxide emissions, although further work is underway to quantify those effects.
The Plantain Potency and Practice programme was launched in 2021 and is led by DairyNZ with funding from New Zealand’s Ministry for Primary Industries, DairyNZ, PGG Wrightson Seeds and Fonterra.
Research was conducted in partnership with Lincoln University, Massey University, Lincoln Agritech and the Bioeconomy Science Institute.
