WEED SUPPRESSION, GROWTH AND YIELD ATTRIBUTES AND YIELD OF DIRECT SEEDED RICE (ORYZA SATIVA L.) AS INFLUENCED BY NITROGEN RATES AND HERBICIDE SEQUENCE

Weeds are major constraints for increasing productivity of direct seeded rice (DSR) in dry field. Nitrogen fertilization and herbicide selectivity play significant role in deciding the weed dynamics and level of weed infestation. With the said view in mind, for management of weeds and enhanced performance of DSR, a field study was conducted in split plot design with three replications. Main plot comprised of three nitrogen rates (120, 150, and 180 kg/ha), whereas, sub-plot included single application of pendimethalin (PRE), sequential application of PRE fb bispyribac sodium/penoxsulam/metsulfuron + chlorimuron (almix) [POST] and two controls (weedy check and weed free). N-rates affected the growth of weed species, but total density and biomass were not affected. Sub-optimal (120 kg/ha) and supra-optimal (180 kg/ha) nitrogen rates enhanced biomass of Cynodon dactylon (L.) Pers. and Echinochloa colonum (L.) Link. but in Caesulia axilliaris Roxb. density and biomass decreased at supra-optimal N-rate. However, density of Cyperus rotundus L. increased at optimal N-rate (150 kg kg/ha). Supra optimal rate of N-application enhanced plant height, biomass, tiller count, total grain, filled grain, panicle count, biological yield, straw yield and weed index of DSR. Amongst herbicides, sequential application of pendimethalin fb penoxulam produced lowest density and biomass of C. rotundus, E. colonum, C. axillaris. Moreover, this treatment reduced density and biomass of total weed by 70.14 and 53.66 per cent over weedy check, and consistently produced higher growth, yield attributes and yield of DSR. However, antagonistic interaction between PRE and all tested post emergence herbicide were observed for the management of C. dactylon.