Efeito de herbicidas e competição de plantas daninhas na morfofisiologia do feijoeiro

Abstract

Farmers have faced challenges in controlling weeds that infest common bean crops, primarily due to the lack of registered herbicides for this purpose. Thus, the objective of this study was to evaluate the effect of herbicide use and weed competition on the morphophysiology of the black bean cultivar SCS 204 Predileto. The experiment was conducted in a randomized block design with four replications. The treatments used were: bentazon (720 g ha-1); bentazon + imazamox (600 + 28 g ha-1); fomesafen + fluazifop-p-butyl (200 + 200 g ha-1); fluazifop-p-butyl (187.5 g ha-1); clethodim (108 g ha-1); and pinoxaden (40 g ha-1); bentazon + fluazifop-p-butyl (720 + 187.5 g ha-1); bentazon + clethodim (720 + 108 g ha-1); bentazon + pinoxaden (720 + 40 g ha-1); bentazon + imazamox + fluazifop-p-butyl (600 + 28 + 187.5 g ha-1); bentazon + imazamox + clethodim (600 + 28 + 108 g ha-1); bentazon + imazamox + pinoxaden (600 + 28 + 40 g ha-1); and bentazon + imazamox + fomesafen + fluazifop-p-butyl (600 + 28 + 200 + 200 g ha-1). To evaluate weed competition, the following treatments were used: bean (weeded control), bean + papuã, bean + buva, bean + bindweed, bean + pigweed, and bean + papuã + buva + bindweed + pigweed. At 7, 14, and 21 days after treatment application (DAT), the phytotoxicity to the bean crop was evaluated. At 45 days after emergence, gas exchange, leaf area, and shoot dry mass were determined. Additionally, nutrient accumulation in the bean plant's leaf tissues, such as nitrogen, phosphorus, and potassium, was measured. The herbicides fluazifop-p-butyl, clethodim, and pinoxaden caused less phytotoxicity to the bean cultivar SCS 204 Predileto. The highest phytotoxicity was caused by the application of fomesafen + fluazifop-p-butyl and imazamox + fomesafen + fluazifop-p-butyl to the beans. Clethodim and pinoxaden promoted greater accumulation of leaf area and shoot dry mass in the SCS 204 Predileto bean cultivar. Weeds in competition with beans (bean + papuã + buva + bindweed + pigweed) caused greater accumulation of leaf area and less shoot dry mass in the crop. The competition of bean + bindweed and the application of the herbicides imazamox + fomesafen + fluazifop-p-butyl had the least negative effects on the physiological variables (photosynthetic activity and carboxylation efficiency) of the crop.