Effect of weed management in rice (Oryza sativa) and its carryover effect on succeeding blackgram (Phaseolus mungo) crop

An experiment was conducted during rabi and summer seasons of 1993-95 to st udy the direct and carryover effect of herbicides in rice (Oryza sativa L.) -blackgram (Phaseolus mungo L.) cropping sequence. Two pre-transplanting sp ray of glyphosate (1.5 kg ai/ha at each spray) with oxyflourfen (pre-emerge nce) 0.1 ai/ha + handweeding (40 DAT) being statistically on par with two p re-transplant spray of glyphosate 1.5 ai/ha + oxyfluorfen (pre-emergence) 0 .1 ai/ha + 2,4-D sodium salt 0.75 ai/ha post-emergence (21 DAT) and 2 pre-t ransplanting of spray of glyphosate + 2 handweedings (20 and 40 DAT) proved significantly superior to any of these 3 treatments without glyphosate in reducing weed population and their dry weight, thus resulting in highest ri ce grain yield (5.6 t/ha). Carryover effect of rice herbicides on the succe eding blackgram was not significant in controlling grass and broadleaved we eds. However, sedge population in blackgram under glyphosate was significan tly lower resulting in lesser weed dry weight than that of no glyphosate an d gave significantly higher blackgram seed yield (10.1 t/ha).