Investigations on the allelopathic influence of eupatorium (Chromolaena odorata(L.) King and Robinson and utilization as organic manure

Abstract

Lab and field experiments were conducted at the Instructional Farm, College of Agriculture, Vellayani during June 2001 to February 2002 to study the allelopathic influence of eupatorium (Chromolaena odorata (L.) King and Robinson) on important field crops and weed species and to investigate the potential of the weed biomass as organic manure. In Experiment I, allelopathic influence of eupatorium on three important field crops ie., rice (Oryza sativa L.), cowpea (Vigna unguiculata (L.) Walp.) and Bittergourd (Momordica charantia L.) and two weed species. ie ., Thatch grass (lmperata cylindrica (L.) Beauv.) and eupatorium (Chromofaena odorata (L.) King and Robinson) was studied. The treatments comprised of aqueous plant part leachates of fresh and decayed eupatorium at five and ten per cent co ncentr at io n. The results revealed that aqueous fresh plant part leachates inhibited germination and early seedling growth of rice, cowpea and bittergourd severely. Germination of thatch grass and eupatorium were also suppressed by the treatments. In general, the aqueous fresh plant part leachates showed greater effect than the decayed plant part leachates, and the effect was more -with leaf leachate. The inhibitory effect was more with the higher concentration of the leachate. Under Experiment II, field observations were made to study the biology of eupatorium under Kerala conditions. Composting of mature eupatorium was tried and the response of bhindi to eupatorium as compost and green leaf manure was observed in comparison with poultry manure, vermicompost, coirpith compost and farmyard manure. The results revealed that eupatorium took about 293 days from germination to seed maturity under Kerala conditions. The plant flowering was during December - January and seeds dispersed in the months of February - March. Each plant produced about 25,000 seeds on an average and had a germination percentage of about 30 per cent. When the mature and dried eupatorium weed biomass was composted, the C : N ratio came down from 62.72 to 18.88 in four months and was ready for use as organic manure. The NPK content of the composted material was 0.76, 0.58 and 0.81 per cent respectively. The yield response of bhindi to eupatorium as organic manure revealed that eupatorium compost was on par with poultry manure and farmyard manure treatments. However when the fresh weed biomass was used as green leaf manure, the yield was considerably lower. The results indicated the need and usefulness of composting the weed biomass before using it as sole source of organic manure in bhindi.