WEEDS IN SOYBEAN CULTIVATION WITH DIFFERENT PREDECESSOR COVER CROPS

Abstract

The competition between soybean and weeds affects crop development due to reduced resources such as water, light, and nutrients, leading to yield losses. Thus, the study aimed to evaluate quantitatively and qualitatively, through phytosociology and seed bank, the weed presence in a soybean cultivation area with different predecessor cover crops. The experiment was installed under no-till system conditions using a randomized block design with nine treatments and three replications. The treatments were composed of the following cover crops, sorghum (Sorghum bicolor), crotalaria (Crotalaria ochroleuca), millet (Pennisetum americanum), Urochloa ruziziensis, U. brizantha cv. Piatã, fodder radish (Raphanus sativus L.), U. brizantha cv. Xaraés, millet + fodder radish, and fallow. The soybean crop was established on the cover crops in the 2019/20 harvest. Soybean characteristics, the seed bank, and weed phytosociology were evaluated. The highest soybean yield was obtained with U. ruziziensis as predecessor cover crop, reaching 4530 kg ha-1. It was concluded that the following cover crops, sorghum, crotalaria, and millet, were the ones that most suppressed the soil weed seed bank. Contrarily, the fallow provided the greatest viable seed number. The weed species Eleusine indica, Digitaria insularis, and Cenchrus echinatus had higher phytosociological values in all treatments.