In recent years the popularity and number of cover crops, companion crops, and living mulches, have exploded and deciphering practical applications can prove quite the challenge. AHDB's Strategic Cereal Farms are embarking on a journey to unravel the intricacies and integrate these options effectively into their agricultural ventures.
Joe Martlew, AHDB's Senior Knowledge Transfer Manager, explains that one of the key goals of the programme is to help farmers best select cover crops which suit their farm.
During a recent webinar, a spotlight was cast on the latest results from the Strategic Cereal Farms. Nitrate losses took centre stage, with Nathan Morris (NIAB) and Brian Barker (the first Strategic Cereal Farm East host) presenting the conclusive results from on-farm trials featuring cover crops.
Farm-specific objectives guided the choice and management of cover crop species, with a focus on reducing nitrate and pesticide losses to drainage water. The trials, spanning several harvest years (2018–22), compared cover crops oil radish and rye against over-winter stubble and ploughed bare ground. Cultivation approaches, encompassing ploughing and a one-pass system, were also scrutinised.
Nathan revealed that average losses ranged from 0.1 to 0.8 kg of nitrogen per day across the experiment. The extremes in these trials illustrated potential cash losses, emphasizing the financial impact of nitrate losses on the farm.
Cover crops, grass leys, winter oilseed rape, and winter barley emerged as heroes, reducing nitrate losses by up to 50% compared to stubble. The trials underscored the value of maintaining soil cover with living crops. Notably, lower-disturbance, one-pass cultivations exhibited a 55–66% reduction in nitrates in drainage water compared to ploughing.
Moving on to biodiversity benefits, Fiona Burnett (SRUC) and David Aglen (Strategic Cereal Farm Scotland host) delved into the impact of cover crop management on soil health, biodiversity, and cash crop establishment of spring barley. The use of cover crops for four years yielded minor improvements in soil health and enhanced water-retaining capacity.
Sustaining cover crops into spring positively impacted beneficial insects, particularly ground beetles and spiders. The trials demonstrated that different timings of cover crop destruction had minimal effects on spring barley, with the drilling date proving to be the key yield driver. However, negative effects associated with drilling spring barley into a living cover crop prompted its removal from trials.
Elizabeth Stockdale (NIAB) and David Miller (Strategic Cereal Farm South) reported on experiments with cover crops in extensive regenerative systems. Collaborating with South East Water and the Farming & Wildlife Advisory Group (FWAG) since 2020, the trials showcased consistent reductions in peak nitrate concentration with overwinter cover crops compared to stubble alone.
Buckwheat-containing mixes exhibited consistent performance, emphasising the need to align species with specific challenges. Notably, cover crop treatments improved soil structure, increased worm numbers, and fostered beneficial organisms, outweighing minor drawbacks like an increase in slug populations.
In essence, cover crops emerged as valuable contributors to soil health and biodiversity without compromising cash-crop performance. Their role in reducing nitrate leaching, coupled with appropriate cultivation choices, was evident. Early establishment and timely destruction of cover crops appeared optimal for spring-crop performance, striking a balance that enhances soil health benefits without impeding subsequent cash crops. The key takeaway is a nuanced understanding of cover crops, aligning their selection with farm objectives to navigate the agricultural landscape successfully.
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