RESPONSE OF TRANSPLANT AMAN RICE VARIETIES TO RATES OF TWO EARLY POST-EMERGENCE HERBICIDES

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from July to December 2013 to study the response of transplant aman rice varieties to rates of two early post-emergence herbicides. The experiment was laid out in a split plot design with three replications. The experimental treatments comprised three varieties, viz., BINA dhan7, BRRI dhan49, BRRI dhan57; and eight herbicide treatments,viz., hand weeding, no weeding, Pyrazosulfuron ethyl @150gha^-1, Pyrazosulfuron ethyl @300gha^-1, Pyrazosulfuron ethyl @450gha^-1, Orthosulfamuron ethyl @150 gha^-1, Orthosulfamuron ethyl @300g ha^-1, Orthosulfamuron ethyl @450gha^-1. Early post emergence applications of Pyrazosulfuron ethyl and Orthosulfamuron ethylwere done at 14 DAT. Varieties differed significantly in all the crop parameters and grain yield was highest in BINA dhan7. Herbicide treatment had significant effect on all the crop parameters except 1000-grain weight. Pyrazosulfuron ethyl @150gha^-1 and 300gha^-1 did not have any toxic effect on rice plant but @450gha^-1 showed temporary slight yellowing of leaves which recovered within 5-7 days. On the other hand, the higher dose of Orthosulfamuron had no toxic effect on rice plant. Orthosulfamuron @450gha^-1 produced the highest grain yield. Interaction between herbicide treatment and variety differed significantly in all the studied crop parameters except 1000-grain weight. BINA dhan7 with Orthosulfamuron @450 gha^-1 gave the highest grain yield.