J. Expt. Biosci. 7(1):23-32, January 2016 ISSN 223-9626 (Online). ISSN 2077-3358 (Print) 23 EXAMINING ALLELOPATHIC EFFECT OF FRESH MIKANIA (Mikania micrantha) ADDITION TO SOIL ON CYPEROUS WEEDS IN KHARIF SEASON M.J. Ullah 1 *, J. Rahman 2 , M. Yeasmin 3 , K. Fatima 4 , M. Quamruzzaman 5 *Corresponding author, E-mail: Jafarullahsau@gmail.com Abstract A study was carried out at the weed museum of Sher-e-Bangla Agricultural University, Dhaka to evaluate the allelopathic effect of mikania on Cyperaceous weeds during kharif season of 2013. Soil from the wheat field was collected, sun dried and mixed with mikania fresh plants at 6 different rates of mikania application (T0 = no mikania, T2 = 2%, T4 = 4%, T6 = 6%, T8 = 8% and T10 = 10%, all of sundried soil by weight) and allowed the weed seeds within the soil to germinate and grow in burried (into soil of the weed museum) earthen pots. Cyperus rotundus, Cyperus esculentus and Fymbristylis miliacea comprised the cyperaceous weeds. Results showed that total number of Cyperaceous weeds either increased from 30 DAS or remained constant up to 60 DAS. It drastically reduced from 60 (92-205 per pot) to 90 DAS (30-205 per pot) showing 76, 64 and 72% reduction in above ground, root and total dry matter of the Cyperous, respectively. Mikania application showed a progressively reduced population density of Cyperous per pot with the consecutive increase in mikania rates at all the growth stages. Unlike number, the dry weight of Cyperous was not significantly affected by mikania application. Mikania application at 2% showed always lower dry weight of Cyperous weeds at all the growth stages than the control with dry weights of 4.72, 9.42, 12.90 and 3.28 g per pot by T2 against the values of 5.75, 9.75, 16.66 and 5.64 g per pot by control at the respective growth stages. Relative percentage of number of Cyperous weeds did not vary remarkably showing a range of 68.01-73% and 68.83-75.78% at 30 and 45 DAS, respectively. At 60 and 90 DAS, the relative number of Cyperous weeds showed reduced values (61.90 and 20.10) due to mikania application showing higher value in the control pot (67.25 and 51.96%, respectively). Likewise mikania application showed reduced relative percentage by weight of Cyperous weeds (10.40-12.40%) at 30 DAS showing the highest relative percentage by weight in control (14.2%). Mikania application increased weed control efficiency by number at 30, 45 and 60 DAS showing 14.45-56.32% over the control one. However, the weed control efficiency by weight of Cyperous was found in most of the cases negative except with T2 indicating that addition of fresh mikania over 2% by weight did not contribute to weed control judged by weed weight. Key words: Mikania, Allelopathy and Cyperous weeds. Introduction In the crop fields weeds are one of the main pests reducing crop yield from 15 to over 96% (Staff, 2009). In Bangladesh, weeds in crop fields are mainly controlled by using human labourer. Urbanization, industrialization along with huge developmental works made a continued scarcity of agricultural labourers especially in the peak periods. As such labourers are very expensive and make agriculture enterprises non-profitable. So it is urgently necessary to find out alternative ways to control weeds. One alternative is to use herbicides which give rise to environmental hazards. Again in Bangladesh, weed control by using any implements has not been yet feasible due to either unavailability of appropriate implements or inability of farmers to buy weeding implement(s) as the Bangladeshi farmers do not afford much. 1 Professor 3 Lecturer 5 MS student, Department of Agronomy 2 Professor, Department of Genetics and Plant Breeding, 4 Freelance Researcher, Current Address: Ph. D. Fellow, Department of Agronomy, Sher-e-Bangla Agricultural University, Dhaka-1207.