Eficiencia de herbicidas preemergentes bajo diferentes situaciones de rastrojo de arroz

In rice systems where stubble is retained, combining weed control practices before and during the crop cycle may affect crop establishment, weed pressure, and grain yield. This study aimed to evaluate the effects of autumn herbicide application, stubble level, and different in-crop herbicide sequences on rice establishment, the dynamics of Echinochloa spp. and non-grass weeds, final weed infestation, and grain yield.

The experiment was conducted in Paso Farías, Artigas, Uruguay, during the 2024–2025 growing season. Treatments comprised conditions with and without autumn herbicide application, three stubble levels, and four herbicide sequences, evaluated in 72 plots arranged in three blocks. Assessments included initial crop density, weed density before and after the postemergence application, final weed-infestation score, and grain yield. Data were analyzed using mixed models and nonparametric tests according to the nature of each response variable.

Preemergence management affected crop establishment, with lower plant density under the clomazone plus pendimethalin sequence than under the no-preemergence condition. Autumn application consistently reduced Echinochloa spp. density. Non-grass weeds responded mainly at the second assessment to stubble level and herbicide sequence, with lower densities under the double-stubble condition and the imazapyr plus imazapic sequence. Herbicide treatments produced overall differences in final weed infestation, although no specific treatment pairs differed. Grain yield depended on the combination of practices: without autumn application, stubble reduced yield relative to the no-stubble condition; with autumn application, differences among stubble levels disappeared and two herbicide sequences outyielded the untreated control.

Overall, the evaluated practices did not produce a uniform response across all variables; their effects depended on the weed group, assessment time, and combination of management practices. Because the study was conducted at a single site during one growing season, extrapolation of the results requires validation across additional environments and years.