EFFICACY OF HERBICIDES IN NON-PUDDLED TRANSPLANTED RICE UNDER CONSERVATION AGRICULTURE SYSTEMS AND THEIR EFFECT ON ESTABLISHMENT OF THE SUCCEEDING CROPS

Transplanting of rice seedlings in non-puddled soil under conservation agriculture systems is a new promising technology for which effective and economic weed control strategies have to develop. Therefore, a study was conducted in wet season rice during 2013 and 2014 with some commonly used pre- and post-emergence rice herbicides (pyrazosulfuron-ethyl, butachlor, orthosulfamuron, acetochlor + bensulfuron methyl, butachlor + propanil and 2,4-D amine) in strip tilled non-puddled field condition at Mymensingh, Bangladesh to evaluate their weed control efficacy singly or in sequences, their cost-effectiveness and residual effect on the succeeding crops like wheat and lentil. Sole application of herbicide was less effective to control all types of weed species than sequentially applied herbicides. Sequential application of pre- and late post-emergence, early post- and late post-emergence or pre-, early and late post-emergence herbicides controlled weeds by 46-98% and 43-95%, respectively in terms of weed density and biomass. Sequential application of pyrazosulfuron-ethyl followed by orthosulfamuron and butachlor + propanil provided the most effective and economic weed control under this new rice establishment practice. Moreover, the study suggested a range of effective herbicides for strip-tilled non-puddled wet season rice, but possible rotation of those herbicides in a sequential application is needed. Additionally, residue of those herbicides did not show any adverse effect on the succeeding crops of rice like wheat and lentil. However, further research is needed with various new molecules of herbicide and their residual effect on the subsequent crop as well as soil environment.