Effect of Soil Amendments and Botanicals on the Performance of Spring Onions (Allium Fistulosum L.) and Control of Onion Thrips (Thrips Tabaci)

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2011-06-19
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Abstract
Two field experiments were conducted during the 2009 minor rainy season and 2010 major rainy season at the experimental field of the Department of Horticulture, Kwame Nkrumah University of Science and Technology, Kumasi to study the effect of soil amendments and botanicals on the growth, yield and quality (crude protein, crude fibre, fat and ash) of spring onions (Allium fistulosum L) and the efficacy of the botanicals in controlling onion thrips (Thrips tabaci). The experiment was a 3 x 3 factorial laid out in a Randomized Complete Block Design (RCBD) with three replications. The treatments consisted of three types of soil amendments (Poultry manure, Green manure and No manure) and three types of botanicals (Moringa leaf extract, Neemazal and No botanical). The number of leaves, number of daughter shoots, plant height and yield were the parameters studied in both experiments. In the minor season, no significant differences were observed in the parameters studied as affected by soil amendments, except plant height at harvest, where poultry manure and green manure treated plots produced taller plants (40.81cm) and (39.88cm) respectively than the control (no manure) (34.85cm). Botanicals did not significantly influence growth and yield of spring onion in the first experiment, however, the number of leaves damaged by thrips was significantly reduced by the botanicals, where neemazal was the most effective in the control of onion thrips against leaf damage. The highest net benefit of GH¢ 6600 was obtained by poultry manure plots sprayed with neemazal while the lowest net benefit of GH¢ 2430 was obtained by green manure plots sprayed with moringa leaf extract. In the major season experiment, soil amendment significantly increased the number of leaves, number of daughter shoots, height and yield of spring onion where poultry manure treated plots produced the highest number of leaves (17.23), number of daughter shoots (4.25), the tallest plants (41.16cm) and highest yield (2.68t/ha). Plots which were not treated with any manure produced the lowest yield, number of leaves, number of daughter shoots and plant height. Botanicals again did not significantly influence growth and yield of spring onion in the second experiment but the number of leaves damaged by thrips was significantly reduced by the botanicals. Neemazal and moringa leaf extract were more effective. The highest net benefit (GH¢ 714) was recorded by poultry manure treatments which were not sprayed with any botanical. Poultry manure appears to be the most important and cost effective organic manure in this study, the use of which should be encouraged in both the minor and major rainy seasons. Neemazal and moringa leaf extracts were found to be effective in reducing the number of leaves damaged by onion thrips in the minor and major rainy seasons by preventing them from feeding and causing damage to the leaves of spring onion.
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A thesis submitted to the School of Research and Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi Ghana in partial fulfillment of the requirements for the award of Master of Science (Olericulture) degree, 2011
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