Influence of winter cover crop residue management on weeds and yield in pepper (Capsicum annuum L.) in a Mediterranean environment Emanuele Radicetti, Roberto Mancinelli, Enio Campiglia * Dipartimento di Scienze e Tecnologie per l’Agricoltura, le Foreste, la Natura e l’Energia, Università della Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy article info Article history: Received 8 March 2012 Received in revised form 24 April 2013 Accepted 13 May 2013 Keywords: No-tillage Minimum tillage Conventional tillage Green manuring Mulching Integrated weed management abstract 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 þ 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. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Recent interest in cover crops has been motivated by the in- crease of the cost of commercial fertilizers and pesticides, the decline in soil fertility and the loss of soil, nutrients and chemicals that become major contaminants to water sources (Hartwig and Ammon, 2002). Therefore the use of cover crops and their resi- dues is becoming an interesting practice not only among organic vegetable growers, but also on conventional farms, especially where an integrated weed management is required (Campiglia et al., 2012). In the Mediterranean environment, annual winter cover crops are planted in the late summer or early autumn, become established before winter, and reach the highest level of biomass by early spring (Campiglia et al., 2011a). They can generally provide biological weed control throughout their growing period by replacing an unmanageable weed population with manageable cover crop aboveground biomass (Teasdale and Mohler, 2000). To avoid competition with a subsequent cash crop, winter cover crops are usually suppressed in spring by chemical and/or mechanical means. Before planting spring vegetables, cover crop residues could be tilled into the soil as green manure or killed and left on the soil surface as organic dead mulches in no-till crop production systems. When incorporated into the soil, many cover crop species are known to release allelochemicals that can reduce weed emergence and growth (Kruidhof et al., 2009). When left on the soil surface, organic dead mulches can inhibit weed growth not only by * Corresponding author. Tel.: þ39 0761 357538; fax: þ39 0761 357558. E-mail address: campigli@unitus.it (E. Campiglia). Contents lists available at SciVerse ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cropro.2013.05.010 Crop Protection 52 (2013) 64e71