Comparative Efficiency and Selectivity of Herbicides in Okra¹

Field experiments were conducted for two seasons (spring and kharif, 1973) with okra (Abelmoschus esculentue (L.) Moench, ‘Pusa Sawani’) at the Agricultural Research Institute, Sabour (Bihar) to evaluate the efficiency and selectivity of pre-emergence application of alachlor (2-chloro-2. 6-diethyl-N (methoxymethyl) acetanilide) at 1 kg/ha, nitrofen (2, 4-dichlorophenyl 4-nitrophenyl ether) at 0.5 kg/ha and their combinations with one hand-weeding or post-emergence application of MSMA (monosodium acid methanearsonate) at 0.7 kg/ha. Repeated weeding and an unweeded check were also included for comparisons. The period between 30 and 60 days after sowing the crop was the most critical period for weed competition. Application of alachlor controlled most of the weeds and particularly the annual grasses which dominated in both the seasons. However, one hand-weeding combined with nitrofen or alachlor was found to be more effective in controlling the annual grasses for longer duration and lower weed-index.

Green fruit yield in unweeded control was reduced to 60.47 and [49.06 per cent in the spring and kharif seasons respectively. Use of alachlor was found as effective as repeated weeding in increasing the fruit yield in spring season whereas in kharif season addition of one hand-weeding with alachlor or nitrofen applied as pre-emergence was found essential for getting the higher yield