Improving Soil Properties and Growth of Casuarina Equisetifolia through Use of Biochar, Manure and Inorganic Fertilizer in Kilifi County, Kenya

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dc.contributor.advisorBenson E. Mochogeen_US
dc.contributor.advisorBenjamin O. Odangaen_US
dc.contributor.authorMwadalu, Riziki Umazi
dc.date.accessioned2023-08-08T09:35:44Z
dc.date.available2023-08-08T09:35:44Z
dc.date.issued2023
dc.descriptionA Research Thesis Submitted in Partial Fulfilment of the Requirements for the Award of Doctor of Philosophy (Integrated Soil Fertility Management) in the School of Agriculture and Environmental Sciences, Kenyatta University May, 2023en_US
dc.description.abstractSoil fertility challenges coupled with frequent droughts in arid and semi-arid lands (ASALs) have led to massive crop failures thereby increasing the problem of food insecurity. As climate change unfolds, there is a need for technologies that boost soil moisture while enhancing soil fertility. Biochar has been reported to be an effective soil amendment with the capability of enhancing soil productivity. However, the impact of biochar on tree growth is still outstanding. Therefore, the present study aimed at evaluating the potential of biochar, manure, and NPK to enhance Casuarina equisetifolia (Casuarina) growth at different growth stages through nursery and field experiments using randomized complete block experimental design. The nursery experiment evaluated the effects of 0% biochar (control), 10% biochar, 20% biochar, 10% manure, 10% biochar + 10% manure, and 20% biochar + 10% manure on Casuarina growth at the seedling stage. The field experiment evaluated the effects of four biochar rates (0, 2.5, 5.0, and 7.5 t ha-1), 5 t ha-1manure, 50 kg ha-1 of NPK, and a combination of the different biochar rates with manure and NPK on Casuarina growth and soil physical-biochemical properties. All treatments were replicated thrice. At the seedling stage, seedlings treated with 10% manure significantly enhanced Casuarina height by up to 46.8% and collar diameter by up to 30.7% compared to the control (p<0.05). For the field experiment, 7.5 t ha-1 biochar treatment yielded a higher Casuarina height of < 23.4% than the unamended treatment. The lowest biochar rate of 2.5 t ha-1 yielded a higher collar diameter of < 30.2% in comparison with the unamended treatment. Largely, soil bulk density decreased with biochar application by <23.2% compared to the unamended treatment after utilization of the highest biochar rate. The use of 7.5 t ha-1 biochar yielded the highest soil moisture content, which increased by up to 108% compared to the untreated control across the assessment periods. In terms of biochar’s impact on soil chemical properties, there was substantial soil pH improvement of up to 21.3% after biochar application of 7.5 t ha-1; there was an increase of up to 1.3 pH units. Total nitrogen increased by 32.4% after biochar addition while total carbon increased by four-fold. Available phosphorus and Cation exchange capacity (CEC) increased by up to 263.7% and up to 95.2%, respectively, following biochar application. Soil bacteria increase by up to 32.6% and fungi by up to 47.6% after biochar utilization in comparison with the unamended treatment. Ameliorating soil with 7.5 t ha-1 biochar yielded higher Casuarina height than the sole application of NPK. These results strongly suggest optimal growth of Casuarina seedlings requires the application of manure with high nutrient contents at the seedling stage while the application of biochar at field establishment has the potential to enhance the growth of Casuarina and improve soil physical-biochemical properties.en_US
dc.description.sponsorshipKenyatta Universityen_US
dc.identifier.urihttp://ir-library.ku.ac.ke/handle/123456789/26618
dc.language.isoenen_US
dc.publisherKenyatta Universityen_US
dc.subjectImproving Soil Propertiesen_US
dc.subjectGrowthen_US
dc.subjectCasuarina Equisetifoliaen_US
dc.subjectBiocharen_US
dc.subjectManureen_US
dc.subjectInorganic Fertilizeren_US
dc.subjectKilifi Countyen_US
dc.subjectKenyaen_US
dc.titleImproving Soil Properties and Growth of Casuarina Equisetifolia through Use of Biochar, Manure and Inorganic Fertilizer in Kilifi County, Kenyaen_US
dc.typeThesisen_US
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