Effect of Jatropha cake and inorganic fertilizer on the growth and yield of Jatropha curcas (L.) A

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Since the surge of interest in renewable energy alternatives to liquid fossil fuels, attention has been paid to the possibility of growing Jatropha curcas, for the purpose of producing biofuel. The seed of Jatropha curcas contains 30% oil that can be used in standard diesel engines. Jatropha biodiesel being a profitable alternative, it has attracted many multinational companies into Ghana with the quest of establishing jatropha plantations. In line with the Bioenergy Policy of Ghana, the government is collaborating with the private sector to develop about one million hectares of jatropha plantation throughout the country. The need therefore arises as to how to improve the yield of jatropha through agronomic techniques such as fertilization to produce enough oil to contribute to the energy requirements of the nation. Few studies on its utilization have proven that jatropha bio-waste (cake) has the potential as a fertilizer. This study was therefore carried out at the Agricultural Research Station at Awomaso, under the College of Agriculture and Natural Resources (CANR), Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana, to investigate the effect of different levels of jatropha cake and their combinations with NPK 15:15:15 on the growth and yield of Jatropha curcas plants. A Randomized Complete Block Design (RCBD) with three replicates was used and twelve treatments applied. Results of a one year study showed a significant (P < 0.05) vegetative growth (number of leaves, stem height, stem diameter and number of branches) response of Jatropha curcas to all the fertilized treatments except lower levels of NPK (T1= 250 Kg/ha). Early growth responses were observed in plants that received either NPK only or their combinations with jatropha cake. Later, plants that received lower levels of NPK showed similar vegetative growth as controls while their combinations with jatropha cake still performed better. Plants that received jatropha cake only responded late but recorded similar stem heights, stem diameters vi and number of branches as those that received NPK fertilizers and their combinations with jatropha cake. The combination of both organic and inorganic amendments ensured increased vegetative growth at all stages of the plant’s life. Also early flowering as well as fruiting occurred in all fertilized plants but did not translate into higher seed yield. The results of the effects of the various treatments and the plants on the soil’s physical and chemical properties showed no significant differences (p>0.05) between any of the treatments in soil characteristics after two years. When compared to the initial soil properties however, all the treatments had significantly higher (p<0.05) pH values than the initial. The results reported in this work indicate that fertilizer application can induce higher and faster vegetative growth but not seed yields in the first year of the plant’s establishment. Also fertilization does not affect the soil’s physical and chemical properties. However, the jatropha plant can reduce soil acidity after two years of establishment.
A thesis submitted to the Board of Graduate Studies, Kwame Nkrumah University of Science and Technology in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Philosophy in Agroforestry.