Cover crops - a practical solution to improve water quality
Tillage farmers were reminded of the important role cover crops can play in the protection of water quality, more specifically nitrate capture, at the Teagasc National Tillage Conference, held yesterday, January 29, in Co. Kilkenny.
Addressing the gathered delegates, Senior Research Officer and Agronomist on the Teagasc Agricultural Catchments Programme, Dr. Bridget Lynch shared some of the key benefits of cover cropping, and reminded farmers of the key water quality metrics that need achieving.
Dr. Bridget Lynch, pictured above, provided an update on cover cropping in the Agricultural Catchments Programme and the Impact of Farming for Water EIP measure at the Teagasc National Tillage Conference on January 28.
As set out in the Water Framework Directive, Dr. Lynch explained, all waters must reach ‘good’ or ‘high’ ecological status by 2027. Adding complications to this is the level of nitrates present in some river bodies. According to the EPAs Water Quality in 2023: AN Indicators Report 42% of waters have unsatisfactory nitrate concentrates, while the south east region has the highest nitrate concentrations associated with agriculture, coupled with freely draining soils and lower effective rainfall.
Bringing this data back to a more local level and sharing some of the steps farmers in the Castledockrell Catchment – an arable dominant catchment that has an average N concentration in its river of 6.98 mg/L nitrate-N, Dr. Lynch examined how schemes such as GLAS, ACRES and the Farming for Water EIP has seen an increased uptake of farmers growing catch crops in the catchment and its surrounds.
“Teagasc research has shown that overwinter cover crops are effective at reducing N leaching,” Dr. Lynch explained, “and farmers in the Castledockrell Catchment and its surrounds have increased the area grown under cover crops by 87% in 2024 compared to 2023, aided by financial incentives under ACRES coupled with and the Farming for Water EIP.
“In the north of the Castledockrell Catchment, we’ve seen an improvement in nitrate concentrates in the groundwater since 2018. However, for achievements to be witnessed across the entire catchment and other catchments nationally, we need consecutive years of good cover crop area to make an impact at river water scale,” Dr. Lynch added.
Dr. Lynch also shared some key tips on establishing cover crops, noting that sowing date has an impact on nitrate losses. Earlier sowing dates allow for more biomass production, hence facilitating more nitrogen capture. Sharing data from a nitrate leaching study which took place within the Castledockrell catchment in 2022, which compared both biomass N uptake and nitrate leaching losses, Dr. Lynch illustrated (figure 1 below) how nitrate losses are lower when a leafy turnip and forage rape mix are established over leaving the ground fallow and allowing for natural regeneration to occur.
Figure 1: Nitrate-N leaching study
