Effect of Sulfonylurea Herbicides Applied Alone and Tank Mix with Metribuzin on Weeds in Wheatand their Residual Effect on Succeeding Crop of Sorghum

Field experiments were conducted during 1996–97 and 1997–98 at the Agronomy Research Farm of Chaudhary Charan Singh Haryana Agricultural University, Hisar to evaluate the efficacy of sulfonylurea herbicides alone and in combination with other herbicides for controlling weeds in wheat and their carryover effects on growth and quality of succeeding sorghum crop. Season long crop-weed competition reduced the grain yield by 30.97–33.12% as compared to weed free environment. All the weed control treatments resulted in significant increase in grain yield over weedy check owing to lesser crop-weed competition in both the seasons. Application of chlorsulfuron at 30 g ha⁻¹, metsulfuronmethyl at 8 g ha⁻¹ and combined application of chlorsulfuron and metribuzin at 15+100 g ha⁻¹ and 15+200 g ha⁻¹ resulted in complete control of composite weed flora, thereby giving, yield as good as weed free environment. Metribuzin alone at 200 and 400 g ha⁻¹ and in combination with metsulfuron-methyl at 2 g ha⁻¹ proved phytotoxic to wheat plants. Growth of sorghum grown after wheat was significantly affected due to the residues of chlorsulfuron at 30 g ha⁻¹ followed by metribuzin at 400 g ha⁻¹ during second year of experimentation, which needs further experimentation under different climatic conditions in view to confirm their residual behaviour for succeeding crops. Quality constituents of fodder sorghum viz., tannin, in vitro dry matter digestibility were significantly affected in all the herbicide treated plots except metsulfuron-methyl.