Comparative studies on the effects of three cultural practices on growth, yield and nutritive qualities of vegetable jute (Corchorus Olitorius L.) and lettuce (Lactuca Sativa L.)

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The effects of spacing, weed competition and irrigation frequency on growth, yield and nutrient composition of vegetable jute (Corchorus olitorius L.) and lettuce (Lactuca sativa L.) were investigated. The spacing’s investigated were 30 x 15cm, 30 x 22.5cm and 30 x 30cm; the weeding frequencies were, i) no weeding, ii) weeding once, iii) weeding two times and iv) complete weed-free conditions achieved by 4 weedings and irrigation were at 1, l½, 2, 2½ and 3 days intervals. Data were collected on plant height, canopy spread, stem girth, total leaf area, root length, root spread and volume, leaf/stem ratio, yield and yield components of the vegetables. Determinations of dry matter content, crude protein, ash, crude fibre and mineral elements including vitamin C, calcium, magnesium, potassium and phosphorus were carried out. The economics of the various cultural practices were also evaluated. Vegetable jute had higher values for all the nutrient elements studied, suggesting that vegetable jute is more nutritious than lettuce. The vegetative growth and yield responses of vegetable jute and lettuce were variable. The results indicated that the highest yield and profit were obtained at the closest spacing of 30cm x 15cm. Spacing, however, did not significantly influence crude protein, ash, crude fibre and phosphorus contents of plants. Magnesium, calcium, and potassium contents tended to decrease with decreasing spacing while vitamin C content increased with decreasing spacing. The performance of plants grown on plots weeded two times and those kept weed-free throughout growth were comparable in both vegetative growth and yield parameters. It was more profitable to weed two times than to keep plots weed-free throughout growth. Plots which were not weeded throughout growth resulted in 65% and 95% loss in total yield of vegetable jute and lettuce respectively. Lettuce plants kept either weed-free or weeded two times gave the highest income and profit. Weed competition did not significantly affect dry matter, vitamin C, potassium and magnesium contents of plants but crude protein, ash and crude fibre contents increased with increasing frequency of weeding. The contents of magnesium, potassium and phosphorus in vegetable jute leaves tended to decrease with increasing frequency of weeding. With regard to the irrigation frequencies, daily irrigation produced the highest yield and profit in lettuce while vegetable jute recorded losses under any of the irrigation frequencies studied. Crude protein, ash, and phosphorus contents were not significantly influenced by irrigation frequency but dry matter, potassium, calcium and magnesium contents decreased with decreasing frequency of irrigation in both vegetable jute and lettuce.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy in Olericulture, 1998