Leguminous living mulches present a potential ‘multifunctional’ solution that could provide benefits for arable production and the environment. In addition to contributing to soil nitrogen availability through nitrogen fixation, when used and managed well, living mulches can have many positive impacts on biotic and abiotic soil health. They have been shown to improve soil fertility, add organic matter to the soil, improve soil structure and tilth, while reducing soil erosion, surface water pollution and weed burden on the crop. Beneficial micro- and macro-fauna, including earthworm numbers, can be positively affected, especially where living mulch use is accompanied by conservation tillage. Such benefits, however, can only be achieved with good management of the living mulch, and challenges remain in establishment, competition, management of pernicious weeds, such as thistles and docks, and slugs. These must be overcome in order to optimise living mulch use and uptake in arable production.
A key aspect of clover living mulch management is the initial selection of the clover type under-sown with the crop, as different clover types each have varying characteristics. For example, ease of establishment, tolerance of sowing depths, competitiveness (against both crop and weeds), persistence, root structure and depth differ across different clover species. Another such characteristic is the height and growth habit a clover can achieve. This is an important consideration, as it can affect harvest complexity when the crop has matured. White clover, for example, is a relatively low-lying perennial, while berseem clover achieves greater plant height but is not particularly frost tolerant. Taller, more competitive clovers or clovers with a tendency to intersperse with crop stems, such as red clover, for example, may not be as suitable for use with relatively short crops, such as cereals, where they could make combining more difficult, but their competitiveness may be of no consequence to a taller crop such as maize.
The TRUE Case Study at STC aims to look at management of in-crop clover living mulches within crop growing seasons, and in a broad range of broad-acre crops. It evaluates the impacts of existing agronomic regimes and practices (against weeds, for example) on the living mulch and its subsequent impact on crop agronomy and soil health indicators. It will also investigate the potential of novel Precision Agriculture Technology-assisted machinery solutions to optimise management. In the past cropping season at STC, clover living mulches were established in a spring barley crop and a fodder maize crop using strip-tillage (a conservation and minimum tillage technique, where soil is only disturbed in the area that will contain the crop seed row). Three types of clover were evaluated: white, berseem and red clover. The season was characterised by a cold, wet start to the spring, which delayed drilling, and a hot, dry summer with drought conditions – challenging conditions for clover living mulch establishment! Data has not yet been analysed, but while establishment in the spring barley crop was patchy, with white clover seemingly performing best, all clover types in the maize established well. This may be because clover germinates best with some moisture in soil. It is possible that shading effects from the maize crop influenced clover establishment, protecting soil from rapid drying and improving conditions for establishing clover seedlings.
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