Weed control in rice remains a critical challenge in direct-seeded rice cultivation. This study combined field and laboratory experiments to compare the efficacy of nine herbicide combinations against weeds in dryland rice fields and to evaluate their impact on rice economic traits. A model was constructed using principal component analysis for comprehensive evaluation, aiming to identify optimal herbicide combinations for direct-seeded rice under shallow drip irrigation in Hinggan League. The results indicate that pendimethalin provides better pre-emergence control compared to oxadiargyl and pretilachlor. The combination of florpyrauxifen-benzyl + benzobicyclon provided optimal weed control efficacy and rice economic performance when applied as a foliar treatment. Forty-five days after application, weed control efficacy against Echinochloa crus-galli (L.) P. Beauv. and Amaranthus retroflexus L. was 72% and 85%, respectively, with fresh weight reduction of 63%. Theoretical yield reached 4285.48 kg·ha−1. At rice harvest, no herbicide residues were detected in rice straw or grains across all treatments, confirming the safety of the applied treatment for rice. Principal component analysis (PCA) was used to evaluate the comprehensive scores of each treatment, with pendimethalin + florpyrauxifen-benzyl + benzobicyclon achieving the highest score of 0.65. The study indicates that the combination of pendimethalin as a pre-emergence and florpyrauxifen-benzyl + benzobicyclon offers significant advantages in weed control efficacy and rice growth, achieving the highest comprehensive evaluation score. This combination holds important application value for weed control and grain yield assurance in direct-seeded rice fields.
Li et al. (Sun,) studied this question.