Composição e distribuição da flora de plantas daninhas na cultura do milho sob diferentes plantas de cobertura

Abstract

The straw in the soil brings a series of benefits to the agricultural production system, such as, for example, suppressing the germination of weeds, due to the physical barrier and also for releasing allelopathic substances with effects of inhibiting the germination of these species. Weeds are one of the main obstacles for crops to achieve high productivity, because if they are not properly controlled, they can bring losses of up to 80% of production, in addition to the abundance of biotypes of weeds with resistance that have been selected by abusive use. and incorrect use of herbicides. Thus, the objective was to evaluate the effects of cover crop straw on the composition and distribution of weed flora at the beginning of maize crop development. The experiment was carried out in randomized blocks, with four replications, consisting of five treatments cultivated before the corn crop, as follows: I) Brachiaria (Brachiaria ruziziensis), II) Crotalaria (Crotalaria ochroleuca), III) Pigeon pea (Cajanus cajan), IV) Brachiaria + Guandu-dwarf, V) control. At 16 and 45 days after corn sowing, phytosociological analyzes were carried out in order to identify and quantify weeds and calculate the species importance value index. At 15 and 30 days after corn sowing, plant height and leaf area of corn were evaluated. Most weeds were absent in treatments with straw, but some species such as bitter grass (Digitaria insularis), trapoeraba (Commelina benghalensis), black beggartick (Bidens pilosa) and mint (Ageratum conyzoides) had rates of relatively significant values of importance. The mulch of all treatments was efficient in the suppression of white poaia (Richardia brasiliensis), morning glory (Ipomoea acuminata), crabgrass (Digitaria horizontalis) and butterflies (Cenchrus echinatus). The results prove the change in the community of weeds grown in soil with mulch and help in the development of weed management programs, including cover crops in the production system to reduce the use of herbicides in the western region of Paraná.