Auxinic and sulfonyl urea herbicides for post-emergence control of sedges and broad-leaf weeds in direct-seeded rice

Abstract

There is a shift of dominance from grasses to broad-leaf weeds and sedges in direct-seeded rice (DSR) due to the continuous use of grass herbicides. The uncontrolled growth of broad-leaf weeds and sedges in DSR throughout the entire crop season resulted in a 52–64% reduction in crop yield. Field studies were carried out to evaluate control of sedges and broad-leaf weeds with post-emergence application of 8, 12, 16 g ha⁻¹ of metsulfuron; 435, 580, 725 g ha⁻¹ of 2,4-dimethyl amine salt; 2, 4, 6 g ha⁻¹ of pre-mix of metsulfuron plus chlorimuron, and azimsulfuron 20 g ha⁻¹ in direct-seeded rice. The post-emergence application of azimsulfuron 20 g, metsulfuron plus chlorimuron 4 g and 2,4-D amine salt 725 g ha⁻¹ effectively reduced density and biomass of Cyperus rotundus L., C. iria L., Phyllanthus niruri L., Alternanthera philoxeroides (Mart.) Griseb., Mollugo nudicaulis Lam., Digera arvensis Forsk., Caesulia axillaris Roxb. and Ammannia baccifera L. Metsulfuron 16 g ha⁻¹ as post-emergence resulted in effective control (92.2–98.9%) of broad-leaf weeds but gave partial control (19.8–37.1%) of sedges. The maximum grain yield was recorded in weed-free treatment and it was statistically similar to grain yield obtained with post-emergence use of azimsulfuron 20 g or metsulfuron plus chlorimuron 4–6 g or 2,4-D amine salt 580–725 g ha⁻¹ herbicides. It is concluded that post-emergence use of 2,4-D amine salt 725 g or metsulfuron plus chlorimuron 4 g ha⁻¹ is efficient and economical herbicides for control of broad-leaf weeds and sedges in direct-seeded rice.