QUANTIFICATION OF ALLELOPATHIC POTENTIAL OF DIFFERENT CROP RESIDUES FOR THE PURPLE NUTSEDGE SUPPRESSION

Crop residues are well known for their chemical (allelopathic) and physical effects on crops and weeds.Allelopathic potential of different crop residues viz. sorghum, sunflower, brassica (applied alone or in combination) for the purple nutsedge (Cyperus rotundus L.) suppression was investigated in a pot study. Chopped residues were incorporated at 12 t ha-1 (6 g kg-1 of the soil) into the soil and a weedy check was also maintained. There were six tubers of purple nutsedge in each soil filled pot. Soil incorporation of all the residues substantially delayed the tuber sprouting. Nonetheless combinations of residues showed were more effective in purple nutsedge suppression than sole application of either of them. Sorghum and brassica residues, when applied in combination did not allow any tuber to sprout. There was substantial suppression in final germination by 41-45% from sole application and 27-100% from combination of crop residues. These residues exerted a pronounced negative influence on the shoot and root length by 21-100 and 17-100%, respectively. Likewise, there was 50-100% and 47-100% suppression in shoot and root dry weights, respectively. Hence, this soil incorporation of allelopathic crop residues may be employed in the integrated approach for purple nutsedge management.