Plantain's high water content means a cow's urine is more diluted, enabling the nitrate to spread over a greater area of pasture; the nitrogen consumed is portioned differently in the animal's body so less makes it into the urine; and mechanisms within the crop's root system lock more of the nitrate up in the soil.
Without new tools like plantain, many dairy farmers in the catchment may struggle to meet council nitrogen-leaching targets – which is why DairyNZ has begun the potentially game-changing research project.
"Plantain did well, so we're now including it in our regular re-grassing programme," says McNaughton. "We're re-grassing about 12 per cent of the pasture a year, incorporating 2kg plantain with 25kg ryegrass and 4kg clover.
"Plantain has deep roots and is drought-tolerant, which is good for us because we're not irrigated and it can get very dry here in the summer."
Reducing nitrogen leaching in streams (like the Raparapawai Stream on McNaughton's property) will contribute to improving water quality across the catchment.
"…it will be a big step to plant [the targeted] 30 per cent plantain," says McNaughton. "To some extent, it will come down to cost. Herbs are just another species in the paddock but if the trials are successful, we'll aim to gradually increase plantain in our pastures until we reach 30 per cent."
Neighbour Blair Castles says when he found out DairyNZ was suggesting plantain, he was keen to get on board: "To reach Horizons Regional Council targets, we have to reduce nitrogen leaching on our farm by 8-9 kilograms per hectare (kg/ha). All of us in the region need to get on board and do our best to be compliant."
In the upper Manawatu, a significant proportion of dairy farms are faced with reducing nitrogen leaching by an average of 60 per cent to meet targets outlined in the council's One Plan – a massive challenge.
DairyNZ's Tararua Plantain Project is helping farmers keep on top of nitrogen leaching, fast-tracking development of science through simultaneous research (locally and on research farms), recognising the size and urgency of the tasks ahead.
It's one of three catchment-specific projects helping farmers reduce their farms' environmental footprint. Paddock-scale research has begun on six farms and findings will be shared with other farmers in the area.
DairyNZ catchment engagement leader Adam Duker says: "Plantain is an excellent low-cost opportunity to make a positive impact on the One Plan targets at farm and catchment levels. This project will help farmers to make plantain work in their systems, with the aim to significantly reduce nitrogen loss while maintaining farm profit.
"We have an ambitious goal to have 95 per cent of unconsented farmers in the district with 30 per cent or more plantain in their cows' diets by 2025.
Castles has been using plantain, along with chicory, for about six years. He's looking at taking out chicory and lifting the rate of plantain. At present, chicory is 10 per cent of his sward; plantain about the same.
"It wasn't difficult to establish but it's been very effective. We wanted to use more herbs in our 'fruit salad' pasture of ryegrass and clovers. We've achieved this and the cows like it. Depending on the trials, we could increase plantain in the future. We'll do anything we can to be compliant with the council regulations."
Another local farmer, Mark Diamond, has been using plantain for three years. In a 10ha trial, he's using about 2kg plantain/ha as part of a mixed sward with ryegrass and clover.
"Plantain is easy to grow and is part of our ongoing re-grassing plan," he says. "It's easier to manage than chicory and the cows love it."
Diamond says farmers know they must make changes but, because every property is different, there's no 'one size fits all' solution: "We all live in houses of different shapes and sizes with different coloured roofs. Farms are much the same. Brad's property is completely different to mine, even though we share a boundary fence.
"It's definitely a hard one. Some farms have higher rainfall than others and there are different options available to help reduce leaching, like off-paddock infrastructure and changes to farm systems – but these all come at a cost."
Other members of the research team include Professor Peter Kemp and a team from Massey University's School of Agriculture and Environment and Horizons Regional Council's Dr Nic Peet, strategy and regulation manager.
