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

Abstract

The soybean/corn rotation is the primary grain production system in Brazil, but it is more vulnerable to weed competition compared to crop diversification. Cultural weed control is effective in diversified systems and can improve phytosociological indices while reducing control costs. The aim of this study was to evaluate the phytosociology and costs of weed control in long-term diversified grain production systems. The study was conducted from 2014/2015 to 2022/2023, with six treatments and four replications. Phytosociological indices were calculated in March 2014 and after the soybean harvest in March 2023, identifying and analyzing the importance value indices of the weeds. Soil coverage was analyzed at the end of the period, and weed control costs were calculated based on average values of active ingredients and agricultural operations over the nine years. Systems with winter cereal crops showed lower weed diversity and better control of Commelina benghalensis and Euphorbia heterophylla compared to the soybean/corn rotation. Soil coverage was adequate in all treatments. Costs were higher in the crop succession treatment (US$ 199.24 ha⁻¹ year) compared to the diversified systems (US$ 151.29 ha⁻¹ year). It is concluded that the cultivation of winter cereals is effective in controlling C. benghalensis and E. heterophylla, while crop succession results in higher weed control costs.