A METHODOLOGY FOR EVALUATION OF RESIDUAL EFFECT OF WEED-MANAGEMENT PRACTICES IN RICE (ORYZA-SATIVA) RICE GREENGRAM (PHASEOLUS-RADIATUS) CROPPING SYSTEM

A field experiment was conducted in the wetlands of Coimbatore during 1986-87 and 1987-88 to assess the residual effect of treatments of one crop on the succeeding crops in a rice (Oryza sativa L.)-rice-greengram (Phaseolus radiatus L.) cropping system. Pre-plant paraquat spray 7 days before land preparation of the south-west monsoon rice crop resulted in higher residual effect on the summer crop of greengram. Skipping the basal application of N for 15 days after transplanting and pre-emergence application of butachlor as well as hand-weeding twice in the south-west monsoon rice crop resulted in higher residual effect on the summer greengram. There was no significant residual effect on the north-east monsoon rice crop. Post-emergence application of molinate and hand-weeding twice in the north-cast monsoon crop of rice had higher residual effect on the summer crop of greengram.