Effects of eleven herbicides on the growth and weed control efficacy in autumn-sown pea

Grass damage problems have hindered the spread of peas; chemical herbicides have become an important measure to control weeds on farmlands. However, there is no effective and safe herbicide for controlling weeds in pea fields. So, the study evaluated the effectiveness of 11 herbicides, which included 6 kinds of pre-emergence herbicides (48% trifluralin, 50% acetochlor, 33% pendimethalin, 96% (s)-metolachlor, 50% napropamide, 40% prometryn) and 5 kinds of post emergence herbicides (15% fluazifop-p, 10% quizalofop-p, 12.5% sethoxydim, 10.8% haloxyfop-r-methyl, 12% clethodim), on weed control while cultivating the pea cultivar 'Xiwan-2'. The best concentration of all herbicides was selected, and the clear water application (CK1) and artificial weeding (CK2) as two controls. Field experiments were conducted to investigate weed species, study the effects of different herbicides on weeds control, and discus the effects of herbicides on the growth process, morphological characteristics, and economic benefits of autumn pea. The research showed:1) there were 7 families and 13 species of weeds in autumn pea fields; among them, broadleaf weeds included 9 species accounting for 69.23% of the weeds found. This indicated that weeds species in autumn pea field were more in number and broadleaf weeds were the main ones. Farmers should choose broad-spectrum herbicides based on broad-leaved weeds. Herbicides had different control effects on weed quantity and fresh weight, and there was a positive correlation between them. Among the pre-emergence herbicides, 33% pendimethalin had the best control effect; among the post emergence herbicides, 12% clethodim had the best control effect. 2) From overwintering to flowering, herbicide treatments had significant effects on plant height and relative chlorophyll content of autumn pea; however, from the beginning of the pod stage, the effect was no longer significant. All treatments inhibited the accumulation of dry matter in root, stem, and leaf of autumn pea to varying degrees; at the same time, the rate of movement and translocation of dry matter in stem and leaf organs of autumn pea treated with different herbicides were higher than that of artificial weeding, and the rate of movement and translation of dry matter in leaf was higher than that in stem. 3) Herbicides had no significant effect on yield components such as 100-grain weight and pod length. In addition to a slight decrease in yield caused by 10.8% haloxyfop-r-methyl, the other herbicides showed a certain increase in production; among them, 33% pendimethalin and 12% clethodim could increase the yield of autumn peas by more than 25%. The net income from all herbicide treatments increased; among them, the net income of 33% pendimethalin and 12% clethodim was the highest among the herbicides evaluated. It can be seen that the use of herbicides helps increase the economic benefits to farmers. Combined with efficacy, safety, and economic benefits of herbicides, the synthetic effect of pre-emergence herbicide 33% pendimethalin and post emergence herbicide 12% clethodim in autumn pea fields was the best among all herbicides tested. Under the experimental conditions aimed at controlling weeds in the autumn pea field, use of pre-emergence herbicide 33% pendimethalin and post emergence herbicide 12% clethodim is recommended.