Greenhouse experiments were conducted to investigate the effects of various vermicompost amendments on growth responses and nutrient content of kale (Brassica oleracea Acephala group), radish (Raphanus sativus), and tomato (Solanum lycopersicum L), using a completely randomized design with three crop species, four vermicompost treatments and four replications. The twelve treatment combinations consisted of vermicompost levels of 0, 5, 10, and 15% (v/v) and three crop species, kale, radish and tomato. Plants were grown in pots containing soil in which the respective vermicompost levels were incorporated. Three seeds of each species were sown in each pot and seedlings were thinned to one per pot each, approximately two weeks after germination. Plants were supplied at regular intervals with 300 ml of water to maintain field capacity. Plant height, leaf chlorophyll, stem diameter, and leaf expansion rates were collected at weekly intervals beginning three weeks after planting. Plants were harvested at respective maturity dates, and fresh and dry weights as well as total yield were taken. Root, leaf and fruit samples were collected to determine phenolic and ascorbic acid content. Vermicompost soil amendment significantly increased plant height of kale and radish compared to the control but had no significant effect on the height of tomato plants. Leaf chlorophyll content was also greater among plants receiving vermicompost amendments except that of kale which declined at highest amendment level. Fresh and dry weight of kale increased with levels of vermicompost amendments with the magnitude of increase being greater between the control plants and those amended with 5%. Tap root yield of radish was highest among plants amended with 15% vermicompost but yield was similar among amended treatments. Regardless of the treatment, stem diameter was highest in the last few weeks of measurements. Total phenolic content tended to decrease regardless of species with increasing vermicompost levels and vitamin C increased initially up to 10% level for kale and declined thereafter, while there was a steady decline in radish. These results show that vermicompost amendments above 10% may adversely affect plant height and leaf chlorophyll content, while enhancing overall biomass production, and that phenolic and vitamin C responses varied based on vermicompost levels.
Keywords: Compost, sustainability, soil, organic matter, chlorophyll.
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