WEED INFESTATION OF A SOYBEAN (GLYCINE MAX (L.) MERR.) CROP GROWN UNDER NO-TILLAGE AND USING MULCH FROM VARIOUS COVER CROPS AND ITS MANAGEMENT, INCLUDING REDUCED HERBICIDE RATES

A field study was conducted over the period 2007-2009 on grey-brown podzolic soil (sandy), designated as PWsp, with the granulometric composition of silt and classified in agricultural land suitability class 2. The study evaluated weed infestation of a soybean crop grown under no-tillage with mulch from winter rye, winter oilseed rape, and white mustard as well as using herbicide rates reduced by 25% and 50% in relation to the standard rate (2 L ha(-1)). The studied factors were as follows: I. mulch plant species and mulch management method; II. rates of the foliar herbicide Basagran 600 SL. It is desirable to investigate the influence of these factors on weed infestation of a soybean crop for ecological reasons. The effects of these mulches showed that there was significantly lower weed infestation when the mulch crops had been desiccated, while it was highest when they had been mowed. No significant differences were found in the number of weeds due to the herbicide rates applied. The control treatment was characterized by an extremely low number of species (17) and weed individuals (6.4 weeds m(-2)) in relation to all the mulched plots. The values of the air-dry weight of weeds were much influenced by the herbicide rates. Among the rates applied, only the 75% rate effectively reduced the weed dry weight (by 11.4%).