Weed control strategies and yield response in a pepper crop (Capsicum annuum L.) mulched with hairy vetch (Vicia villosa Roth.) and oat (Avena sativa L.) residues

Organic mulches could be a part of a wide strategy of integrated weed management in vegetable production systems. A 2-year field experiment was carried out in Central Italy with the aim of assessing the effect of grass and legume mulches, coming from winter cover crops, combined with herbicide or mechanical hoeing on weed control, on weed community (density and aboveground biomass of each species), and yield of a pepper crop. Hairy vetch (Vicia villosa Roth), oat (Avena sativa L) and their mixture were sown in early autumn and suppressed in May. The cover crop aboveground biomass was cut and arranged in strips which were used as beds for pepper seedlings transplanted in paired rows. A conventional treatment kept bare during the cover crop growing season with two different levels of nitrogen fertilizer on pepper (0-100 kg ha(-1) of N) was also included. Three weed control treatments were applied between the paired pepper rows 30 days after transplanting: a weed free treatment, glyphosate or mechanical hoeing. Dry matter production at cover crop suppression ranged from 5.3 t ha(-1) in oat to 7.1 t ha(-1) in hairy vetch/oat mixture and the N accumulation ranged from 56 kg ha(-1) in oat to 179 kg ha(-1) in hairy vetch. Within the pepper paired rows, mulch treatments reduced weed density and biomass throughout the pepper cropping season. At harvest, weed density and aboveground biomass within the pepper paired rows ranged from 1.7 to 4.6 plants m(-2) and 28 and 133 gm(-2) of DM, respectively. Oat mulch had the highest weed suppression ability and the lowest species richness. Shannon's index and Shannon evenness. Between the pepper paired rows the mulch treatments had the highest species richness and the most diverse weed community in chemical compared to mechanical weed control. The densities of Portulaca oleracea L and Polygonum aviculare L. were the highest under chemical and mechanical control, respectively. The weeds did not hinder pepper production in hairy vetch and hairy vetch/oat mixture where the yield was similar to that obtained in a conventional weedfree system fertilized with 100 kg ha(-1) of N. Therefore the use of hairy vetch mulches in combination with reduced mechanical or chemical weed control could be a feasible strategy in order to control weeds and to produce high yields in a pepper crop. (C) 2011 Elsevier Ltd. All rights reserved.