Mowing mulches: a means for managing competition?

Leguminous living mulches have been shown to support a broad range of positive effects on biotic and abiotic indicators in broad-acre arable production, including soil health. With their nitrogen-fixing potential, they can also play a role in achieving sustainability goals and targets – for example, by naturally fixing nitrogen into the soil, they can help reduce dependence on artificial nitrogen fertiliser inputs, which in turn can reduce nitrous oxide emissions. Key to achieving such benefits, however, is good management of the clover living mulch, with challenges to achieving this remaining a barrier to uptake within industry.

The management of clover to minimise competition with the cash crop during the growing season is one such challenge. Where this is not appropriately addressed early in the growing season, lover living mulches can rapidly close in on the cash crop, especially where the clover has been previously established. This can lead to reduced establishment rates and, by the end of the growing season, crop yield.

The TRUE Case Study at STC aims to evaluate management options of in-crop clover living mulches. As part of this work, we have under-sown cereal, maize and sugar beet crops with berseem, red and white clovers, using PAT-assisted strip tillage technology to try to overcome early emergence and establishment challenges. The strip till worked the clover seeds, previously broadcast on the soil surface, to a depth at which they would not successfully emerge. Though not fully analysed, preliminary findings suggest that, by allowing the crop a strip with reduced clover coverage at drilling, final yield of the crop was not affected, supporting successful establishment and early growth.   

As part of this work, we have also been working in partnership with Manterra Ltd to investigate machinery solutions that can address challenges raised by management of in-crop clover living mulches throughout a growing season. The aim of this is to investigate whether mowing of clover strips in strip tilled clover living mulch platforms can help manage and mitigate the effect of clover later in the growing season as the crop develops, by ‘knocking it back’. Mowing is already an approach we have previously used in our perennial clover living mulch platforms prior to strip tillage and drilling. It generates organic matter that gets worked into the soil during strip tillage, and by the increased number of worms we have observed in clover plots. We are looking forward to seeing the role that mowing might play throughout the growing season – watch this space!