Nitrate leaching into water is a global issue, therefore practical tools to reduce it from happening are necessary in order to improve water quality.
Researchers from Teagasc investigated the effect of including ribwort plantain with grass-clover for reducing nitrate leaching across a range of Irish soil types.
The two-year, five-soil study tested whether the incorporation of 30% or 50% plantain into a grass-clover sward would reduce the concentration and mass of nitrate loss from a range of contrasting Irish soils.
Overall, the results showed that across a broad range of soils, the inclusion of plantain in grass-clover swards was an effective tool for reducing nitrate leaching losses in pasture systems.
Reducing nitrate leaching
At a 30% plantain inclusion in a grass-clover sward, in year one, nitrate leaching was reduced by 6% and 56% on poorly-drained and well-drained soils, respectively.
The reduction in nitrate leaching increased to over 96% in year two on both poorly and well-drained soils.
However, when the plantain content was increased to 50%, leaching was reduced by 21% in poorly-draining soils and by 78% in free-draining soils in year one, and by 98% for poorly and free draining soils in year two.
The inclusion of plantain also led to a reduction in the number of exceedances of the drinking water Maximum Allowable Concentration in leached water samples collected in the study.
This was down from 28 times with grass clover, to seven times when 30% plantain was included, and to four times with 50% inclusion.
Much of the nitrate loss mitigation effects of plantain could be achieved at the 30 % level and this is likely to be a more practical level to manage on farm compared to the 50% inclusion level.
Lead Teagasc researcher on the study, Dr. Patrick Forrestal of the Teagasc Soils, Environment and Land Use Department, Johnstown Castle, explained:
“These results show that the inclusion of ribwort plantain in grass-clover swards is a promising tool for reducing nitrate leaching losses in a variety of soil types.
“This Irish work aligns with Irish and EU targets to improve water quality and has practical application for reducing nitrate leaching losses in pasture systems.”
Dr. Karl Richards, head of the Teagasc Climate Centre, highlighted that “this exciting research demonstrating a reduction in nitrate leaching from plantain inclusion in grass clover swards is also important for reducing indirect greenhouse gas emissions”.
“Further research is underway quantifying the impact of multi-species swards from both a grassland production and environmental perspective,” he added.
The “Ribwort plantain inclusion reduces nitrate leaching from grass-clover swards; A multi-year five soil study” Teagasc study has recently been released.