Influence of winter cover crop residue management on weeds and yield in pepper (Capsicum annuum L.) in a Mediterranean environment

A cover crop/pepper sequence was adopted for two growing seasons (2009/2010 and 2010/2011) in Central Italy to evaluate the effect of different cover crop species and their residue managements on weed control and fruit yield of a pepper crop. The treatments consisted in: (a) three winter cover crops [hairy vetch (Vicia villosa Roth.), oat (Avena sativa L.), canola (Brassica napus L.)] and bare soil; (b) three cover crop residue managements [residues left in strips on soil surface in no-tillage (NT), green manure residues at 10 cm of soil depth in minimum tillage (MT), and green manure residues at 30 cm of soil depth in conventional tillage (CT)]; (c) three levels of weed management applied to the pepper crop [weed free (WF), inter-row mechanical control applied at 30 days after pepper transplanting (WH), and weedy (W)]. The mulch strips in NT covered 50% of the ground and were used as a transplanting bed for pepper seedlings. At cover crop suppression, hairy vetch showed a higher aboveground biomass compared to oat and canola (on average 792 vs. 526 g m−2 of DM, respectively), even if oat showed the lowest level of weed infestation. In pepper the lowest weed density was found in NT compared to MT and CT (on average 22, 33, 37 plants m−2). Oat residues always caused the lowest weed density and weed aboveground biomass, while hairy vetch showed an efficient weed suppression only inside the pepper rows in NT where the soil was mulched. An inter-row hoeing, carried out 30 days after pepper transplanting, determined a general reduction of weed density and weed aboveground biomass (on average −60 and −86%, respectively) and a higher pepper yield (on average + 84%) compared to weedy pepper. Hairy vetch showed the highest marketable pepper yield among the cover crop treatments, regardless of weed management treatment, and the yield in weedy treatments was higher in NT than MT and CT (on average 31.4 vs. 14.2 t ha−1 of FM, respectively). The pepper yield was positively related to the chlorophyll concentration of the pepper leaves (SPAD readings) which was higher and more constant throughout the pepper cropping period in hairy vetch residues. Therefore, the use of hairy vetch residues placed in mulch strips within row combined with an inter-row cultivation enabled us to obtain a satisfactory weed control and fruit yield in a pepper crop.