Herbicidal Influence of Leaf, Shoot and Root Aqueous Extracts of Chromolaena odorata (L.) King and Robinson on Agronomic Characteristics of Zea mays (L.) and Vigna unguiculata (L.) Walp in South-Eastern Nigeria

Abstract

The study was carried out at the Teaching and Research Laboratory of the Department of Animal and Environmental Biology, Imo State University, Owerri, to determine the Herbicidal influence of Leaf, Shoot and Root aqueous extracts of Chromolaena odorata (L.) King and Robinson on agronomic characteristics of Zea mays and Vigna unguiculata. Ten viable seeds of Z. mays and V. unguiculata were placed in 26 mm Petri dishes lined with cotton wool and moistened with the 0, 2, 4, 6 and 8% concentrations of leaf, shoot and root extracts. The experiment was laid out in Completely Randomized Design and replicated three times. Parameters assayed were seed germination percentage and rate of germination, seedling root and shoot lengths, fresh and dry weights respectively. Results obtained showed a dose-dependent decrease in percentage germination of Z. mays and V. unguiculata.  There was a significant difference (p<0.05) in germination percentage among the plant extracts. Seedling growth was observed to reduce with an increase in extract concentration. Leaf extracts of C. odorata recorded highest inhibitory effects compared to shoot and root extracts. This could be an indication that the leaf extracts contain higher allelochemicals compared to shoot and root. The study suggests that the delayed germination and low germination rate of the test plants after treatment by extracts may be attributed to the allelochemicals present in the extracts which might release phenolics into the soil and these were probably involved in the growth inhibitory effect of surrounding plant species. Thus, C. odorata extracts could be applied as an early post-emergence herbicide for weed control in the tropics. The extracts of C. odorata are safe, bio-degradable and eco-friendly herbicide of plant origin.