Response of weed communities to legume living mulches in winter wheat

In order to obtain information about the impact of legume cover crops on the weed community in organic farming, winter wheat (Triticum aestivum L.) was directly drilled in rows 0.1875 and 0.3750 m apart in living mulches that consisted of Trifolium repens L. (TRFRE), T. subterraneum L. (TRFSU), Medicago truncatula Gaertner (MEDTR), and Lotus corniculatus L. (LOTCO). A control treatment without cover crops (NAT, the site-specific weed community) was also established. The vegetation between the wide rows was either mulched or left undisturbed. The effect of liquid farmyard manure (60 m 3 ha -1 ) was also tested. TRFRE, TRFSU, and LOTCO effectively suppressed Poa annua L. and Matricaria recutita L. at site 1 and P. annua, Capsella bursa-pastoris (L.) Med., and Stellaria media (L.) Vill. at site 2 when compared with NAT. MEDTR, which died during the winter, provided little weed suppression. Mulching significantly suppressed dicotyledonous weed species, but favoured Poa trivialis L. No manure effect was observed. Winter hardy legume cover crops contribute to weed suppression in winter wheat. However, careful evaluation of cover crop x weed x management interactions is necessary to understand the risk for the establishment of problematic weeds.

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