Residual Effects of Herbicides on Sunn Hemp, Peanut and Soybean

Understanding the behavior of herbicides with long residual activity in the soil is essential to promote more judicious application, aiming to minimize environmental impacts on subsequent crops. In this context, this study aimed to evaluate the effects of different doses of the herbicides indaziflam, sulfentrazone and clomazone on the growth and development of sunn hemp (Crotalaria juncea L.), peanut (Arachis hypogaea L.) and soybean (Glycine max (L.) Merr.) plants. The experiment was conducted in a greenhouse following a completely randomized (CRD) experimental design and utilized a 6 × 5 factorial scheme with five replications for each herbicide (indaziflam, sulfentrazone and clomazone) and species (sunn hemp – C. juncea, peanut – A. hypogaea and soybean – G. max). The first factor included six dose levels for each herbicide: indaziflam (12.5, 25, 50, 100 and 200 g ai ha-1), clomazone (157.5, 315, 630, 1260 and 2520 g ai ha-1) and sulfentrazone (75, 150, 300, 600 and 1200 g ai ha-1). The second factor consisted of five crop sowing periods (0, 10, 20, 40 and 60 days after application—DAA). The plants were evaluated for phytotoxicity, leaf area (cm2) and shoot dry biomass (g) at 56 days after sowing. Sunn hemp plants were extremely sensitive to the herbicide indaziflam, regardless of the dose and period of sowing, considering all the analyzed parameters, whereas the phytotoxicity caused by sulfentrazone and clomazone decreased from 20 DAA for all applied doses. Peanut was highly sensitive to the herbicides indaziflam and sulfentrazone, especially at the highest doses, regardless of the sowing period, with reductions in the analyzed parameters. Moreover, soybean was also extremely sensitive to indaziflam, with no significant influence of the dose or sowing period on the analyzed parameters. The same behavior was observed for sulfentrazone applications at 0 and 10 g ai ha-1 at 600 and 1200 g ai ha-1. Therefore, the results indicate different sensitivities of plant species to herbicides, highlighting the high sensitivity of peanut, soybean and sunn hemp to indaziflam and sulfentrazone, regardless of the sowing period. These studies reinforce the importance of ensuring that herbicide use recommendations consider not only the effective control of weeds in the main crops but also the potential risks to subsequent crops.