Phytosociology of weeds in function of different managements of winter cover

Abstract

In order to increase the efficiency of the use of cover crops, it is important to know which species present the greatest suppression of weeds and if the cover crop management method affects the suppression effect. The goal, with this work, was to evaluate the suppressive effect of different winter cover crops and their different managements through the use of phytosociological indices. The experimental design used was of randomized blocks conducted in a 4 × 3 factorial scheme with four replicates. The first factor was constituted by different cover crop species: white oats (Avena sativa), wild radish (Raphanus raphanistrum), vetch (Vicia sativa) and fallow; the second factor was constituted by the cover crop management: chemical control, lodging and no management. The dry matter of the cover crops was quantified at the moment of cover crop management. The weed community was evaluated 75 days after the cover crop management took place, with the assessment of the number of weeds, weed dry matter, relative frequency, relative density, relative dominance, and importance value index (IVI). Oats produces the greatest amount of dry matter. The weed community is compos of 31 species. In the chemical management, oat and vetch cover crops are the ones that suppress the greatest number of weeds. In general, the desiccation allow to a greater number of weeds, but with decrease dry matter. The species Spermacoce latifolia, Conyza bonariensis and Sida rhombifolia present high IVI values. The desiccation of the cover crops may favor herbicide-tolerant species which excel in the environment.