Weed management in sesamum (Sesamum indicum L.)

Abstract

An experiment entitled "Weed management in sesamum (Sesamum indicum L)" was conducted in the summer rice fallows of Rice Research Station, Kayamkulam during 1995. The experiment was laid out in randomised block design with twelve treatments in three replications. The crop was sown on 7.2.1995 and harvested on 4.5.1995. The variety under the experiment was Thilak. The weather condition during the crop growing season was congenial for crop growth and herbicidal treatments. The monocot weeds predominated the experimental area at all stages of crop growth. Next to weed free check, the total weed population till harvest was effectively kept under check and thereby weed control efficiency was maximum with the application of pendimethalin at 1.0 Kg ai ha-1, or alachlor at 1.5 kg ai ka -1 each combined with hand weeding at 30 DAS. But hand weeding twice at 20 and 30 DAS was comparable with these treatments in early stages of crop growth. Weed index was found to be superior with hand weeding twice at 20 and 30 DAS followed by application of pendimethalin at 1.0 Kg ai ha-1 or alachlor at 1.5 Kg ai ha-1, each integrated with hand weeding at 30 DAS. The

plant height was unaffected by weed control at early stages of plant growth. But the plant height at later stages and also the number of branches per plant at all stages of crop growth were maximum with application of pendimethalin at 1.0 Kg ai ha-1 or alachlor at 1.5 Kg ai ha-1, each supplemented with hand weeding at 30 DAS. Leaf area index was not influenced by weed control treatments. The dry matter production of crop at early stages was more with unweeded control, while at later stages hand weeding twice at 20 and 30 DAS followed by the application of pendimethlin at 1.0 Kg ai ha-1 or alachlor at 1.5 Kg ai ha-1 along with hand weeding at 30 DAS. The yield attributing characters like 50 per cent flowering, number of pods per plant, 1000 seed weight and seed yield was superior with hand weeding twice at 20 and 30 DAS closely followed by application of pendimethalin at 1.0 Kg ai ha-1 or alachlor at 1.5 Kg ai ha-1,each coupled with hand weeding at 30 DAS. Although the seed yield and haulm yield were superior with herbicide treatments, the harvest index was not influenced by these treatments. The uptake of nutrients by the weeds were reduced by the weed control treatments which in turn increased the uptake by crop. The nitrogen and phosphorus content of soil was influenced by weed control treatments. The soil bacterial, fungal and actinomycete population at 5 days after herbicidal treatment were significantly superior with cultural practices than the herbicides application. But at 30 days after herbicide application, the bacterial, fungal and actinomycete population in plots receiving cultural methods of weed control were comparable with the corresponding population under some of the herbicide treated plots. With regard to economics of cost of cultivation, higher net income, net returns per rupee invested and benefit-cost

ratio were realised with the treatments involving application of pendimethalin at 1.0Kg ai ha-1, or alachlor at 1.5kg ai ha-1 each integrated with hand weeding at 30 DAS. From the present study, it can thus be concluded with recommendation that the application of either pendimethalin at 1.0 Kg ai ha-l or alachlor at 1.5 kg ai ha-1, each coupled with one hand weeding at 30 DAS would be effective in maximising the yields of sesamum by the efficient control of weeds. These integrated approaches are economically also more suitable over the cultural practices of hand weeding or hoeing in areas with scarcity of labour and high labour cost.