Como fica o posicionamento de herbicidas pré-emergentes na cultura da soja diante de mudanças climáticas e alteração do regime hídrico

Abstract

The synergism achieved through the association of pre-emergent herbicides enables a broader spectrum of weed control, and new formulations can improve herbicide mobility in maize straw + Urochloa ruziziensis. Thus, this study aimed to evaluate the efficacy of pre-emergent herbicide combinations in weed control and their behavior on maize straw + U. ruziziensis under different water regimes. A greenhouse experiment was conducted in a completely randomized design, organized in a 3 × 9 + 1 factorial scheme. The first factor represented water regime intervals: (1) 20 mm of rainfall immediately after application; (2) 20 mm of rainfall 5 days after application; (3) 20 mm of rainfall 10 days after application. The second factor included pre-emergent herbicide treatments: sulfentrazone + clomazone (600 + 540 g a.i. ha⁻¹); flumioxazin + imazetapyr (50 + 106 g a.i. ha⁻¹); pyroxasulfone + flumioxazin (90 + 60 g a.i. ha⁻¹); s-metolachlor + diclosulam (1440 + 29 g a.i. ha⁻¹); flumioxazin + imazetapyr + s-metolachlor (50 + 106 + 1440 g a.i. ha⁻¹); sulfentrazone + diuron (210 + 420 g a.i. ha⁻¹); s-metolachlor + fomesafen (1035 + 228 g a.i. ha⁻¹); s-metolachlor + metribuzin (942 + 224 g a.i. ha⁻¹); s-metolachlor + flumioxazin (52.5 + 1050 g a.i. ha⁻¹), and an untreated control. Evaluations included visual weed control assessments for Amaranthus hybridus, Commelina benghalensis L., Digitaria insularis L., and Eleusine indica. GAMLSS models with different distributions (Gamma, Poisson, and Beta) and specific link functions were used for dry mass analysis, quantitative data, and control, via F-test. Results were processed using R software and visualized with the ggplot2 package. Regarding the days until rainfall, longer waiting periods led to lower control efficacy (<80%) for most herbicides across all species. Notably, Commelina benghalensis exhibited the highest dry mass and control failure, particularly for flumioxazin + imazetapyr + s-metolachlor at 10 days until rainfall. These findings can be attributed to the presence of maize straw + U. ruziziensis, which hindered herbicide translocation to the soil profile, a situation exacerbated by the 10-day dry spell. Therefore, the association of pre-emergent herbicides proved effective for weed control; however, the presence of straw influenced efficacy under suboptimal conditions. It is worth noting that sulfentrazone + clomazone was unaffected by straw or water regimes, achieving the highest control efficiency for all weed species.