Reduced Tillage in Organic Farming Increases Both the Potential Services and Disservices Provided by Arable Weed Communities

ABSTRACT

Arable weeds are a key component of agrobiodiversity, providing both ecosystem services and disservices: while they can reduce crop yields (disservice), they also support higher trophic levels by serving as hosts and providing floral and seed resources that sustain pollinators and natural enemies, alongside additional benefits such as reducing erosion and improving the microclimate (services). Identifying management practices that promote neutral weed communities optimising the trade‐off between their services and disservices, is essential. Organic farming and non‐inversion tillage are promoted for their environmental benefits, but weed management remains a key limitation to wider adoption of reduced tillage (RT) systems. In an organic agronomic trial initiated in 2018, we compared the effect of conventional tillage (CT) resulting in inversion tillage to a maximum depth of 25 cm and RT, defined as non‐inversion tillage at a maximum depth of 10 cm, on weed seed bank and weed standing vegetation, assessing weed species composition, diversity and functional trait‐based potential ecosystem services and disservices calculated by functional trait data extracted from published datasets. Arable weed communities were surveyed during the flowering stage over 3 years (2021–2023) for maize and 2 years (2022–2023) for winter wheat–faba bean. Compared to CT, RT resulted in a denser, richer and more even weed seed bank, without changes in dominant species. In both crops, arable weed standing vegetation under RT showed higher density, species richness and diversity. RT enhanced the potential support of weed communities to pollinators (bees, bumblebees and hoverflies) in maize, while crop‐specific responses were observed in winter wheat–faba bean, with significantly increased support mainly for bumblebees. In both crops, RT consistently increased the potential support to natural enemies (farmland birds, carabid beetles and parasitoid wasps). However, RT also increased the potential competitiveness of weed communities and, in maize, enhanced potential seed bank enrichment, indicating a higher risk of future infestations. As weed communities may still be stabilising following conversion to organic farming, longer‐term monitoring will help confirm whether these patterns persist over time.