Integration Effects of Split Nitrogen Fertilization and Herbicide Application on Weed Management and Wheat Yield

A field study was conducted to determine the integration of split N fertilization and herbicide application on weed management and wheat (Triticum aestivum L.) yield in Shiraz, Iran, in ۲۰۰۵/۲۰۰۶ and ۲۰۰۶/۲۰۰۷ growing seasons. The experimental design was split plot with four replications. Main factors consisted of N timing and splitting, and sub plots included iodosulfuron–methyl–sodium plus mesosulfuron–methyl–sodium, solfosulfuron and two weedy and weed free controls. Compared with the weedy check, iodosulfuron–methyl–sodium plus mesosulfuron–methyl–sodium and solfosulfuron reduced weed biomass by ۶۶% in ۲۰۰۵/۰۶ and ۵۵% in ۲۰۰۶/۰۷, ۳۷% in ۲۰۰۵/۰۶ and ۴۵% in ۲۰۰۶/۰۷, respectively. In all herbicide treatments applied in both years, the highest (۳۵۳.۶ kg h-۱ in ۲۰۰۵/۰۶ and ۲۲۴.۱ kg h-۱ in ۲۰۰۶/۰۷) and the lowest (۶۵.۶ kg h-۱ in ۲۰۰۵/۰۶, and ۲۴.۰ kg h-۱ in ۲۰۰۶/۰۷) weed biomass were obtained from the full N (۳۰۴ kg urea ha-۱) application at tillering stage and zero N application at sowing and stem elongation stages T۱N۰, T۲N۱, T۳N۰ and no N fertilization at sowing, tillering and stem elongation stages T۱N۰, T۲N۰ and T۳N۰. Nitrogen use efficiency of the crop increased when N was split. Consequently, wheat LAI and grain yield increased. However, in the presence of weeds, both LAI and grain yield increases were lower. The results of the present study showed that integration of N and herbicide treatments caused even a higher increase in wheat LAI and grain yield, but resulted in a higher reduction in weed biomass when compared with either treatment alone. N splitting of T۱N½, T۲N½ and T۳N۰ increased wheat grain yield (۶۱% in ۲۰۰۵/۰۶ and ۷۵% in ۲۰۰۶/۰۷), biological yield (۷۶% in ۲۰۰۵/۰۶, ۹۴% in ۲۰۰۶/۰۷), and LAI (۶۲% in ۲۰۰۵/۰۶ and ۲۰۰۶/۰۷). In conclusion, weed control was essential for efficient use of N fertilizer by the crop. Therefore, in order to increase wheat grain yield, integration of split N and herbicide is recommended for the region. The results of this study showed that N splitting treatments of T۱N½, T۲N½, T۳N۰ and iodosulfuron–methyl–sodium plus mesosulfuron–methyl–sodium had the best efficiency in terms of weed control in wheat.

کلیدواژه ها:

Herbicide ، Nitrogen splitting ، Nitrogen timing ، Weed control ، Wheat yield