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 study the direct and carryover effect of herbicides in rice (Oryza sativa L.)-blackgram (Phaseolus mungo L.) cropping sequence. Two pre-transplanting spray of glyphosate (1.5 kg ai/ha at each spray) with oxyflourfen (pre-emergence) 0.1 ai/ha + handweeding (40 DAT) being statistically on par with two pre-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-transplanting 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 rice grain yield (5.6 t/ha). Carryover effect of rice herbicides on the succeeding blackgram was not significant in controlling grass and broadleaved weeds. However, sedge population in blackgram under glyphosate was significantly lower resulting in lesser weed dry weight than that of no glyphosate and gave significantly higher blackgram seed yield (10.1 t/ha).