Plantain 'still a winner' in nitrogen loss battle

Regardless of doubts raised last winter which challenged the interpretation of some of the science supporting plantain’s nitrate busting ability, Brown says farmers can confidently include the herb in their pasture systems and know it reduces N losses.

“We’ve never suggested plantain is the only pasture species that helps in the fight to reduce nitrate leaching in our pasture systems,” he says.

“But there’s 15 years of science and development behind Ecotain (plantain), OverseerFM recognises its ability to reduce N losses and several regional councils do too,” he says.

“For many dairy farmers, maintaining a good percentage of plantain in their farm’s pasture sward is one of the only ways they can fend off the pressure to reduce stocking rate to meet their catchment’s N limit.”

Brown says the questions raised about plantain’s effectiveness created confusion among dairy farmers.

Many had already begun including plantain in their pastures, but Brown says some put their plans on hold because of the uncertainty which developed.

He directs farmers to two “counter-responses” which were published in the New Zealand Journal of Agricultural Research.

One was from scientists working on the Sustainable Food and Fibre Futures Plantain Potency and Practice programme and the other was from a group of scientists from AgResearch.

Brown says both responding groups stood by their earlier trial work which demonstrates plantain (Ecotain environmental plantain) is an effective mitigator of N loss from pasture systems.

He says a mid-term review of the Plantain Potency and Practice Programme, published in September last year, also concluded that plantain reduces nitrate leaching and can help improve freshwater quality.

Farmer Approval

Bay of Plenty dairy farmer Richard Fowler says plantain has helped him maintain the stocking rate and production off his Rotorua Lakes catchment dairy unit.

He operates two 250-cow herd properties, one in the sensitive Rotorua Lakes catchment and another further north near Te Puke, plus a 400ha dairy support and beef unit mid-way between the two dairy units.

He was an early adopter of plantain before its capacity to reduce nitrogen leaching was confirmed by scientists and systems were tested by DairyNZ to guide farmers on how to incorporate it at a farm level.

“We had dabbled in plantain years ago to see if it could help our cows handle facial eczema and grass staggers better. We even sowed it as a crop and used it to grow out our heifers.

“But once DairyNZ started testing different levels of plantain and how to manage it as a way to mitigate N loss, we got stuck in boots and all,” he says.

For the past three years, it has been an integral part of the Rotorua property’s N loss management strategy.

After getting advice from Agricom and looking at the DairyNZ work, he has settled on over-sowing plantain in prillcote form with his spring fertiliser applications at 2kg/ ha of seed (equal to 4kg/ha in prillcote form).

That approach is delivering a reliable 20% component of plantain in the sward across his Rotorua Lakes catchment dairy unit.

“At 20%, we basically get a nitrogen leaching saving equal to 6kg/ha which is a real gain for us, especially in this catchment.

“We’re also wintering more cows off and applying less N fertiliser to help meet our leaching targets but using plantain has been a simple change that’s meant we’re able to maintain our cow numbers,” he says.

Fowler says as long as plantain is recognised within Overseer, he will continue to maintain it at 20% of the pasture sward on his Rotorua Lakes catchment farm to capture the reduction in N loss.

Irish Research

New research just published in Ireland also supports plantain’s positive impact on N leaching and Mark Brown says the results closely align with those from the earlier NZ trials.

The Irish trials investigated nitrate leaching over two years across different soil types from ryegrass-white clover swards with 0, 30 and 50% Ecotain plantain.

On free draining soils, nitrate losses from swards with 30% Ecotain were 56% lower in year one and 96% lower in the second year, compared with the plots with 0% Ecotain. Losses from swards with 50% Ecotain were 78% lower in year one and 98% lower in year two.

The effect in poorly drained soils was much lower in the first year for swards with 30% and 50% Ecotain (6% and 21%), but matched the free draining soil results in the second year at 97% in the 30% swards and 98% in the 50% swards.

In NZ farmlet trials at Lincoln University, plantain mixed swards averaged a 26% reduction in nitrate leaching over three years. At Massey University, the nitrate leaching reduction over four years has also averaged 26% in the plantain mixed swards, ranging from 10% to 42% between treatments.

At both sites, milk production from the plantainryegrass- clover swards has continued at similar levels to those with ryegrass-clover.