Residual do clomazona no solo e influência nas culturas do alho e cebola

Abstract

The presence of herbicide residues in the soil can compromise the establishment of crops such as garlic (Allium sativum L.) and onion (Allium cepa L.) in succession systems. Clomazone, widely used in soybean as a pre-emergence herbicide, plays an important role in reducing the selection pressure of resistant weeds; however, its residual activity may negatively affect sensitive crops grown in succession. Thus, this study aimed to evaluate the residual effect of clomazone on garlic and onion, in order to determine safe intervals between herbicide application and crop planting. The experiment was conducted under field conditions in a sandy clay loam soil. The experimental design was a randomized complete block design with three blocks and seven treatments, corresponding to different intervals between clomazone application (1.5 L ha⁻¹) and crop planting: control treatment (without herbicide), 0, 30, 60, 90, 120, and 150 days after application (DAA), where DAA represents planting on the same day as herbicide application. Phytotoxicity, plant stand, plant height, and yield were evaluated. Data were subjected to analysis of variance assumptions at a 5% significance level. Subsequently, analysis of variance was performed, with stand, height, and yield compared to the control using Dunnett’s test (5%), while phytotoxicity was modeled using exponential regression with a zero asymptote. For garlic, yield did not differ significantly from the control when planting was performed from 30 days after application onwards. Exponential regression indicated a gradual dissipation of the residual effect, with the absence of visual injury symptoms estimated at approximately 75 days after application. For onion, a more sensitive crop, significant yield reductions were observed when planting occurred up to 60 DAA. Exponential regression indicated that residual phytotoxicity may persist for a longer period, with curve stabilization estimated at approximately 120 days after application. These results demonstrate greater tolerance of garlic and higher sensitivity of onion to clomazone. Under the conditions of this study, the results indicate minimum safe intervals of approximately 75 days for garlic and 120 days for onion, which may vary depending on soil texture and edaphoclimatic conditions.