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In Tanzania most of biowaste produced from vegetable and fruits markets are dumped off which results to loss of nutrients and imposing environmental problems. Composting of wastes is important when used as organic fertilizer and benefits the environment by reducing the emission of greenhouse gases. However, little is known about the nutrient content and rate of application of green urban bio-wastes compost sourced from vegetable and fruit markets due to variations attributed to type and source of bio-wastes used. This study therefore, aimed at assessing the effectiveness of green urban bio-wastes compost in increasing productivity and quality of black nightshade and onion crops. A series of studies were carried out to attain the above objective including laboratory work, pot experiments and field trials.
Laboratory work conducted from August to September 2018 to investigate the physical and chemical properties of soil from Tengeru and biowaste compost prepared by Guavay company made from urban bio-wastes collected from open markets. Investigated parameters included: pH, EC, organic carbon, total nitrogen, phosphorus, potassium and micronutrients. Findings from the present study revealed that the pH were 6.21 and 7.11 for soil in CaCl2 and water, respectively and that of green urban biowaste compost were 8.74 and 9.5 in CaCl2 and water, respectively, EC was 0.094 dS/ m for soil and 0.004 dS/ m for green biowaste compost. Total nitrogen was 0.17 % for soil and 1 % for green biowaste compost. Phosphorus and Potassium values were 56.39 mg kg- and 2.86 cmol (+)/kg and 0.07 % and 0. 85 % - 0.91 % for soil and green urban biowaste compost, respectively. Analytical results indicate that the ‘processed bio-wastes’ do not qualify to be called fertilizer because they contain less than 5% of the primary macronutrients the threshold value recognized by soil scientists. Thus N,P and K in bio-wastes compost are not sufficient for crop production since it cannot meet the crops demand hence more ‘inputs’ are required in green bio-wastes to qualify it as a fertilizer.
A pot experiment was conducted to determine the effect of pelletized and non-pelletized urban green biowaste compost on the growth and yield of black nightshade and onion. The treatments tested were: sole application of pelletized and non-pelletized green urban bio waste compost (GUBC) at rates of 0, 200, 400, and 800 mg N kg-1 soil. Also sole application of urea at a rate of 800 mg N kg-1 soil and complementary application of 400 mg N of bio waste and 400 mg N of urea kg of soil were included. The combination of GUBC and urea (400 GUBC + 400 urea) produced the best total number of leaves (58.22) while 800 mg N (urea) kg-1soil and (400 GUBC + 400 urea) mg N kg-1soil produced the best chlorophyll content (60.60 and 58.40 respectively) and 400 (GUBC) mg N kg-1soil produced the tallest plants (33.05 cm) for black night shade. On the other hand onion performed best in terms of both growth and yield parameters under a treatment with a combination of biowaste and urea. For example bulb fresh and dry weight increased from 29.08 g and 24.71 g in control to 130.94 g and 118.69 g in combination of GUBC and urea (400 GUBC + 400 urea) respectively, followed by plants in a treatment with a sole urea whereby the fresh and dry weight of the bulb increased to 95.04 g and 87.71 g respectively. The increase in all cases was highly significant (P≤0.05). However, there was no significance difference (P=0.05) between pelletized and non-pelletized forms of biowaste. The overall results indicate that bio-waste compost was a good soil amendment material for black nightshade and onion production and that the best results are obtained when used together with urea compared to exclusive application of green biowaste compost.
A field experiment was carried out at TARI-Tengeru farm from December 2018 to May 2019 to evaluate the effects of different rates of biowaste compost on growth, development and yield of black nightshade and onion. The experiment was laid out in a randomized complete block design (RCBD) with four different application rates (regarded as treatments) of biowaste compost (GUBC)/urea viz., 0 kg N ha-1, 400 kg N (GUBC) ha-1, 400 kg N (UREA) ha-1 and 200 kg N (GUBC) ha-1 + 200 kg N (UREA) ha-1. Each treatment was replicated three times. Plant growth and yield parameters were used to evaluate the effects of the treatments. Parameters measured were; plant height, leaf number, leaf area and leaf fresh weight for black night shade and bulb size, neck size, bulb fresh weight for onion. The application of a combination of 200 kg N (GUBC) ha-1 + 200 kg N (UREA) ha-1significantly (p=0.05) increased the leaf area and fresh weight for black nightshade, bulb size and bulb weight for onion compared to the rest. Therefore, the use of combination of organic fertilizer and urea is recommended to farmers for improved yield. |
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