Plantain curbs N-leaching
Farmers urged to try a pasture plant that improves environmental outcomes
Adding plantain to pasture won’t completely stop nitrogen leaching but it will help and Rangitı¯kei farmers were urged to try it at a field day this month.
Dairy NZ, Massey University, the Horizons Regional Council and a mob of rural professionals and farmers were among the 40 attenders. The field day was at Ferryview Farm on Parewanui Rd in coastal Rangitikei.
In the Horizons region, there are 170 dairy farms operating without consent, and 35 of those are in coastal Rangitı¯kei. They need to reduce the amount of nitrogen they leach by an average 50 per cent.
Both the industry and the regional council recognise this is not possible, field day written material said, but farmers still need to make an effort. Adding enough plantain to their pasture can make a reduction of up to 89 per cent — without any loss of milk production.
The plantain project aims for the farms to have pasture of at least 30 per cent plantain from January to May, the time of highest leaching.
Plantain ( Plantago lanceolata) is a common pasture plant, and various cultivars have been developed. It can be grown on its own or mixed with clover or with rye grasses. It’s not too fussy about soil nutrients, but will not tolerate being waterlogged.
It handles dry periods better than ryegrass, though the dry can make it fibrous and less palatable. It can be either direct drilled or broadcast sown. Direct drilling is more expensive, but gives better results.
Plantain will last three to five years in pasture if it is managed well, Dairy NZ developer Phillipa Hedley told the group.
It reduces nitrogen leaching in four ways:
One is that it is more coarse and fibrous than grass so cows drink more water when eating it and the nitrogen in their urine is more diluted.
Although plantain contains as much nitrogen as rye grass, there is also less that comes through in urine, due to an unknown action inside the cow’s digestive system.
Thirdly, there’s something about it that slows the conversion of ammonium from urine into nitrates, giving plants more time to take it up and use it.
And fourthly, plantain plants have dense and fibrous roots that simply take up more nitrogen.
The higher the percentage of plantain in pasture, the higher the reduction in leaching.
Some of the best results have been when dilute urine falls on pasture of plantain paired with deep-rooted and fast-growing Italian rye grasses, which “mop up” nitrogen well. Nitrogen leaching can be reduced by 89 per cent then.
Farmers asked whether this difference can be measured by the Overseer computer model. It can’t at the moment, but Horizons policy and regulation manager Nic Peet wants a way of calculating the
Some of the best results have been when dilute urine falls on pasture of plantain paired with deep-rooted and fast-growing Italian rye grasses, which “mop up” nitrogen well. Nitrogen leaching can be reduced by 89 per cent then.
difference very soon.
Farmers were invited to join a working group to increase their use of plantain. They could join as individuals or as a whole catchment.