ADEBAYO E .B (2022) Comparative assessment of plant-based extracts and synthetic insecticides on the growth, yield and proximate composition of cowpea (vigna unguiculata l. walp) institute of ecology and environmental studies, Faculty of Science, Obafemi Awolowo University.
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2022
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Institute of ecology and environmental studies, Faculty of Science, Obafemi Awolowo University.
Abstract
This study assessed the effect of plant-based and synthetic insecticides application on the growth response and yield of cowpea. It also investigated the effects of the insecticides application on the biomass, grain yield and proximate composition of cowpea grains produced. These were with a view to providing information on the use of plant-based extracts on quantity and quality of cowpea grains.
The experiment was conducted on a vacant land measuring 11.75 m x 7.50 m behind the Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife. Viable seeds of Ife-brown cultivar of cowpea were purchased from the Institute of Agricultural Research and Training, Ibadan. The experimental location was cleared manually two times using a cutlass and hand-held hoe. The experiment consisted of four treatments which were: extracts of three plant-based (Azadirachta indica, Tithonia diversifolia, Chromolaena odorata) and cypermethrin that served as control. The extracts of fresh shoots of A. indica, T. diversifolia, and C. odorata were separately prepared using standard method. The experiment was made up of 12 plots, each
measuring 1.5 m x 2.0 m and the plots were arranged in a randomized complete block design. Four seeds per stand were sown using 50 cm x 30 cm spacing and seedlings thinned to 2 stands per hole at 2 weeks after sowing (WAS). The plots were weeded at 3 and 6 WAS. The cowpea stands were sprayed with plant-based and cypermethrin using the rates 100 g/L/plot and 15 mL/L/plot respectively at 5, 6, 7 and 8 WAS. Growth parameters such as plant height, number of leaves and stem girth were measured bi-weekly from 2 to 8 WAS and extent of leaf damage at 7 and 8 WAS.
Tagged cowpea stands were carefully uprooted at 10 WAS to determine the total biomass yield. Cowpea pods were harvested when the pods turned yellow at 10 WAS and threshed. Proximate composition of cowpea grains (crude protein, ash, fibre, carbohydrate, fat and dry matter), preand post-cropped soil analyses were carried out using standard methods. Data obtained were subjected to analysis of variance and their treatment means were separated using Tukey’s multiple comparison test at p < 0.05.
The results showed that pH of the pre-cropped soil was 6.94 and soil texture was loamy sand. Organic carbon and total nitrogen were 0.64 and 5.82 g/kg, respectively and these values reduced to between 13 and 30% across the treatment plots for the post-cropped soil. The growth parameters; height (cm), number of leaves and stem girth (cm) at 6 WAS were: 23.06 ± 0.86, 55.29 ± 4.59 and 1.58 ± 0.05 for A. indica; 24.15 ± 0.75, 57.58 ± 3.94 and 1.69 ± 0.06 for T. diversifolia; 21.76 ± 0.68, 48.38 ± 2.15 and 1.55 ± 0.05 for C. odorata; and 21.99 ± 1.18, 45.26 ± 3.45 and 1.46 ± 0.07 for cypermethrin, respectively. Also, the grain yield of cowpea with cypermethrin, 1.08 t/ha was significantly (p < 0.05) higher than the best plant-based insecticide, T. diversifolia. Cowpea
grains obtained with T. diversifolia and C. odorata had comparable and high values of crude protein (29.7%, 28.3%) and fibre (6.1%, 6.5%) respectively.
The study concluded that T. diversifolia compared favourably with cypermethrin, in terms of grain yield of cowpea, whereas T. diversifolia and C. odorata gave higher proximate composition of cowpea.
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COMPARATIVE ASSESSMENT OF PLANT-BASED EXTRACTS AND SYNTHETIC INSECTICIDES ON THE GROWTH, YIELD AND PROXIMATE COMPOSITION OF COWPEA (Vigna unguiculata L. Walp)