Biodisponibilidade de herbicidas pré-emergentes em solos andinos e seus impactos na produtividade da soja

Abstract

The efficacy of weed control by pre-emergent herbicides depends on the physicochemical characteristics of the molecule, soil attributes, environmental factors, and management practices adopted in the production system. Pre-emergent herbicides can cause phytotoxicity in soybean plants, leading to reduced productivity. Therefore, it is crucial to invest in solutions that ensure better herbicide selection, adjusting the dosage according to soil type while considering the target crop and the history of weed infestations in the area. This approach enables effective weed control without compromising yield. Given this context, the objectives of this study were: 1- To evaluate the bioavailability of the herbicides sulfentrazone, flumioxazin, metribuzin, imazethapyr, and diclosulam in weakly weathered soils; 2- To assess the phytotoxicity and residual control of the pre-emergent herbicides diclosulam, imazethapyr, metribuzin, sulfentrazone + diclosulam, and sulfentrazone at different doses in soybean cultivation. Soil types influenced both the efficacy and phytotoxic potential of the studied herbicides. The herbicides imazethapyr and diclosulam required dose reductions in all tested soils. However, in soil S/A11, the sulfentrazone dose needed to be increased from 200 g a.i. ha⁻¹ to 221.75 g a.i. ha⁻¹, while flumioxazin required an increase from 57.6 g a.i. ha⁻¹ to 95.27 g a.i. ha⁻¹ to achieve 90% control. In soil LE/C6, the flumioxazin dose had to be increased by 103.59% compared to the label recommendation. Furthermore, in soils LE/C6 and H/B22, no dose reduction was observed for sulfentrazone and flumioxazin, respectively. Regarding productivity, differences were observed only among herbicides, with the lowest yields recorded in the diclosulam and metribuzin treatments. Cucumber, wild poinsettia (Chamaesyce hirta), and weed control improved from 15 DAA, influenced by soil moisture. By 90 DAA, all herbicides remained persistent in the soil.