Effects of herbicides on growth, development and yield of different maize varieties

Chemical weed control is convenient for crop field management, but the damage has become increasingly pronounced, especially for herbicides. Field experiments were conducted to study the effects of herbicides on growth process, morphological characteristics, protective enzymes activities and yield traits of different maize varieties in this study. Four widely cultivated maize varieties in the region ('Zhengdan958', 'Xianyu335', 'Jingke968' and 'Jingnongke728') and two herbicides (2, 4-D butyl ester and nicosulfuron) were used in the experiment. No herbicide (manual weeding) was set as CK treatment, the recommended application concentration (optimum concentration) of herbicides was set as T1 treatment and two-times optimum concentration was set as T2 treatment. The herbicides were applied at V4 stage of maize. The results showed that after herbicide application, the growth period of maize varieties prolonged and those of 'Zhengdan958' and 'Xianyu335' were longer than those of 'Jingke968' and 'Jingnongke728'. The growth period of tested maize varieties after applying 2, 4-D butyl ester was longer than that after applying nicosulfuron. After spraying herbicides, leaf area, root length, root surface area and root volume of the tested maize varieties decreased, while the extent of reduction increased with increasing herbicide concentration. Leaf area, root length, root surface area and root volume of 'Zhengdan958' and 'Xianyu335' were lower than those of 'Jingke968' and 'Jingnongke728'. After spraying herbicides, SOD activity, CAT activity and MDA content were significantly different among the tested maize varieties, herbicide type and herbicide dose. SOD and CAT activities of the tested maize varieties decreased, while MDA content increased. With increasing concentration of sprayed herbicides, the effect on protective enzymes activities increased. The decrease in SOD and CAT activities of 'Zhengdan958' and 'Xianyu335' was higher than those of 'Jingke968' and 'Jingnongke728'. Also with increasing concentration, the effect of 2, 4-D butyl ester treatment was higher than that of nicosulfuron. Application of herbicides after seedling resulted in a significant reduction in grain number per ear, 100-grain weight and yield. With increasing herbicide concentration, yield reduction intensified for 'Jingke968', 'Jingnongke728', 'Zhengdan958' and 'Xianyu335', decreased respectively by 8.9%, 9.3%, 14.0% and 16.5% after using 2 times concentration of 2, 4-D butyl ester. However, it decreased by 3.6%, 5.0%, 7.9% and 8.7% after using two times concentration of nicosulfuron, respectively. The reductions in yields of 'Zhengdan958' and 'Xianyu335' were higher than of 'Jingke968' and 'Jingnongke728'. Thus the application of two herbicides after seedling had significant effects on growth period, leaf area, leaf protection enzyme activity, root characteristics, yield and yield composition of maize varieties. The inhibition effect of 2, 4-D butyl on growth and development of maize was higher than that of nicosulfuron. The extent of reduction in leaf area, protective enzyme activity, root traits and yield of the tested varieties increased with increasing application concentration. The reasons for this trend were as follows:the application of herbicides controlled weeds, but also resulted in the accumulation of peroxidation products, destruction of membrane systems, decrease in leaf area, root length, surface area and volume, and acceleration of leaf senescence in the middle and late grain-filling periods of maize. Herbicide tolerance of 'Jingke968' and 'Jingnongke728' were better than that of 'Zhengdan958' and 'Xianyu335'.