Effects of overseeded legume living mulches and tillage on weed suppression and broccoli yield

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Virginia Tech

Experiments were conducted at two sites in Blacksburg, Virginia to study the effects of tillage (conventional plow-disk and no-tillage) and overseeding (underseeding) of legume cover crops (red clover, Trifolium pratense L.; white clover, Trifolium repens L.; and hairy vetch, Vicia villosa Roth.) at transplanting on weed suppression and yield of ’Big Sur’ broccoli (Brassica oleracea var. italica Plenck). In both sites, weed suppression from overseeded red clover, white clover, and hairy vetch equalled or surpassed that of the preemergent herbicide (oxyfluorfen) control. The legumes did not affect broccoli yield components in site 1 nor head number in site 2. However, hairy vetch reduced broccoli yield and head size in site 2. These reductions were attributed to competition with the broccoli. Overseeding tended to delay broccoli yield and head number in the two sites, but this trend was not significant. Tillage system did not affect weed suppression or broccoli yield components, and there were no tillage x overseeding effects. Based on this data, overseeded legumes can provide residual weed control in no-till broccoli, thus allowing a more sustainable production method.