Diversified grain production systems improve phytosociological indices and reduce the cost of weed control

Abstract

The soya bean/maize double-crop is seen as the principal grain production system in Brazil; it is, however, vulnerable to competition and infestation by volunteer plants. In crop rotation systems which include different species, cultural weed control can be effective, improving phytosociological indices and reducing costs. The aim of this study was to evaluate the phytosociology and cost of weed control in a soya bean/maize double-crop and in crop rotation systems with different species, between the 2014/2015 and 2022/2023 crop years. Six treatments were used, with four replications. Phytosociological indices were calculated and analysed following the soybean harvest in 03/2014, 03/2017, 03/2020 and 03/2023. The ground cover was evaluated in 03/2023. The costs of weed control were calculated based on the cost of the active ingredients and the agricultural operations. The treatment that included cereal crops in the winter and grain crops in the summer (T2) showed less weed diversity and greater control of Commelina benghalensis and Euphorbia heterophylla compared to the soya bean/maize double-crop. Each of the treatments had adequate ground cover. Costs in the soya bean/maize double-crop were 22.72% higher for the treatment with cereal crops in the winter and grain crops in the summer (USD 162.32 ha⁻¹ yr^-1). It was found that winter cereals are effective in controlling C. benghalensis and E. heterophylla, and that the soya bean/maize double-crop results in higher costs for weed control.