SHORT-TERM EFFECTS OF CROP HUSBANDRY ON THE WEED COMMUNITY OF A CEREAL-LEGUME ROTATION, “TILMAN-ORG session”

Several agricultural practices can be used to control weed population thus avoiding the use of herbicides. Tillage, fertilization and growth of a green manure are found among them. In the context of a mid-term experiment set up in an organic field in Gallecs (Barcelona), we analysed the effect of chisel vs mouldboard ploughing, application of fertilizer and growth of a green manure on the density of weeds and on composition of the weed community. We evaluated weed density and community composition in April 2012 (spelt crop), February 2013 (green manure cover) and May 2013 (chickpea crop) and also analysed the sources of variation of density for the most abundant species in all periods. Our results show that, under the cereal crop, mouldboard plough had a negative effect on weed densities and also affected weed community composition. While green manure was standing on the field, its presence also had a negative effect on weed density. We found differences in composition between sown and unsown plots. After removal of green manure, though, these effects disappeared. For total weed density in the chickpea crop, we could not find differences due to any of the treatments applied. However, single species analyses showed that Setaria viridis and Polygonum convolvulus responded positively to tillage and fertilization and that P. convolvulus and Convolvulus arvensis were negatively affected by previous presence of green manure. Weed community composition were found to be unaffected by any of our treatments.