Effect of rice husk biochar on maize productivity in the Guinea Savannah Zone of Ghana

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The production and use of biochar presents many opportunities for soil augmentation and carbon sequestration. The potential of biochar as a carbon pool has the ability to sequester carbon in soils and consequently reduce atmospheric concentration of greenhouse gasses. Maize and rice are staple crops produced in Northern Ghana. There is significant biomass available as potential feedstock for biochar production such rice husk, maize stover and cobs; however how much of these residue that could be used for biochar is not documented. The objective of this study was therefore to identify the types of feedstock, the opportunity cost of potential biochar feedstock, some chemical properties of the biochar produced from the rice husk and the effect of the biochar on the growth and yield of maize (Zea mays). The trial consisted of 12 treatments in a split plot experimental design. The main factor is rate of biochar application (0, 2 and 4 t/ha) and the sub-plot was rate of nitrogen application (0, 30, 60 and 90 kg N/ha) with three replications. Sufficient quantities of P and K were applied as basal at 30 kg and 60 kg / ha respectively to ensure that none of these nutrients limited yield. Phosphorus and K were broadcast and incorporated at planting. Phosphorus source was triple superphosphate and the K source was muriate of potash. The data was analyzed with GenSTAT 2008 and where the effect was significant the least significant difference (LSD) was used to separate the means. The survey indicated that the potential feedstock available are maize stover, maize cobs, groundnut shell, rice husk, rice straw, shea nut shell, guinea corn stover and cowpea shell. The opportunity cost of using this potential feedstock for biochar preparation is low. Generally, trend of soil moisture content increased with the rate of biochar application in the order control < 2t/ha biochar < 4t/ha biochar. The application of biochar with inorganic fertilizers increased maize biomass production. Maize plant height and girth were increased significantly when biochar and inorganic N were applied. The yield obtained by combination of biochar and inorganic fertilizer was in significantly higher than the sole application of either biochar or inorganic fertilizer. The soil pH at the end of the experiment increased in all the treatments. Soil total N, % C and ECEC increased within all the treatments. Application of biochar resulted in less than 30% N recovery in the grain, husk and cob with all the treatment combinations. The addition of biochar 2t/ha and 4t/ha increased the grain yield and improved water use efficiency of the maize crop. Biochar can be used as a component in integrated soil fertility management to increase crop productivity.  
A thesis submitted to the Department of Agroforestry, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Science