Black Soldier Fly Frass Fertilizer, Rhizobia Inoculant and Phymyx Effects on Soil Chemical Properties and Bean Yield in Kiambu County, Kenya

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Date
2024-11
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Kenyatta University
Abstract
Globally, bush bean (Phaseolus vulgaris L.) is a highly valued pulse crop that is utilized as an income earner, and for subsistence to address the global food security bottleneck. A key challenge to achieving maximum bush bean yield in the tropical region is soil degradation, due to limited soil micro and macro nutrients such as iron, soil phosphorus (P) in addition to low biological nitrogen fixation (BNF). Studies have demonstrated that soil nutrients especially P and micronutrients can be made available for crop uptake using black soldier fly frass fertilizer (BSFFF), and increased BNF success. Knowledge about BSFFF performance on leguminous crops such as bush beans is, however, scarce. This study assessed the relative performance of BSFFF and a commercial organic fertilizer (Phymyx) on growth, yield, BNF, and N uptake. Phymyx and BSFFF were supplied at the rates of 15, 30, and 45 kg nitrogen ha−1 . In addition, NPK fertilizer was applied at 40 kg N ha−1 , 46 kg P ha−1 , and 60 kg K ha−1 to function as a positive control and unfertilized plots as negative controls. In addition, Rhizobia inoculant was integrated into the experimental set-up to determine its interaction effects with organic and mineral fertilizers. Bush beans grown using BSFFF were the tallest (55.6 cm), with the broadest leaves (124.9 cm2 ), and the highest chlorophyll content (45.5 SPAD-Soil and Plant Analysis Development values). The utmost number of pods (24 pods) and seeds per pod (4 seeds) were achieved in plots that received BSFFF at the rate of 45 kg N ha−1 . Moreover, the application of BSFFF at 45 kg N ha−1 led to a 6, 8, and 18% increase in 100-seed mass, compared with NPK, with the equivalent rate of Phymyx and control, respectively. There were 67, 43, and 72% increases in seed yield in plots that received 45 kg N ha−1 of BSFFF, in comparison with those fertilized using a similar rate of Phymyx, NPK, and control, respectively. The total number of root nodules was 16, 10, and 27 times higher in BSFFF treatment supplied at 30 kg N ha−1 relative to a comparable rate of Phymyx, NPK, and control, respectively. Application of 45 kg N ha−1 from BSFFF also resulted in increased bush bean N uptake by 56 and 45% compared with Phymyx and NPK, respectively. Similarly, there was a 3–14 times increase in the number of effective root nodules and 25–60 kg more N fixed ha−1 in treatments fertilized using BSFFF at 30 kg N ha−1 compared with treatments with similar rate of Phymyx, and NPK as well as the control. The study revealed that using BSFFF in the production of bush beans can result in a $ 271–327 and 12–207% increase in gross and net income, respectively, compared with Phymyx fertilizer. In addition, using BSFFF can result in a 12–118% increase in the gross margin than if Phymyx is used for bush bean production. Therefore, the study showed that application of BSFFF could lead to 5–22 times higher returns on investment than the use of Phymyx for bush bean production. Hence, the findings demonstrate that BSFFF is more effective than NPK and Phymyx at improving the productivity of bush beans and is more economically viable compared with commercial organic fertilizer. This study lays a scientific foundation for adopting effective organic fertilizers like BSFFF for application in bush bean production systems
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Supervisors: 1. Harun Gitari 2.Denis Biseegemukamu 3.Chrystantus Tanga
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