The Effects of Integrated Soil Fertility Management Practices in Enhancing Sorghum Yields

Abstract Sorghum stands as a fundamental food and cash crop in Tharaka-Nithi, yet its production remains suboptimal due to soil fertility limitations. Globally, sorghum yields hover around 2.5 t/ha, indicating an untapped potential given its maximum yield potential of 5 t/ha. Kenya has witnessed a decline in sorghum yields from 0.95 t/ha to 0.78 t/ha, primarily attributed to inadequate soil fertility management and agronomic practices. Most soil management interventions have traditionally focused on singular practices, leaving gaps in understanding the efficacy of integrated approaches. This study sought to evaluate the impact of integrated soil fertility management practices on sorghum and green gram yield in Tharaka-Nithi County. The study was conducted in Nairobi Ndogo and Kairini Farm, the study employed a 3 x 5 factorial experiment in a Randomized Complete Block Design, different fertilizer types and cropping systems. Results, analyzed using Statistical Analysis Software version 9.4, demonstrated significant (p < 0.05) effects of integrated soil fertility management on sorghum yield. Stover yields ranged from 1.93 t/ha to 0.28 t/ha and 7.18 t/ha to 1.35 t/ha at Nairobi Ndogo and Kairini farm, respectively, with the MBILI intercropping technique and NPK fertilizer yielding highest stover. Similarly, grain yields varied from 0.68 t/ha to 0.08 t/ha and 4.01 t/ha to 0.25 t/ha at Nairobi Ndogo and Kairini farm, respectively, with conventional intercropping and NPK plus Zinc fertilizer emerging as optimal treatments. In green gram yields, monocrop green gram and NPK fertilizer demonstrating superior performance. The analysis of treatment effect showed that the means for green gram stover yield ranged from 0.47 t/ha to 0.07 t/ha and 6.70 t/ha to 1.62 t/ha for Nairobi Ndogo and Kairini farm, respectively. The treatment with monocrop green gram, NPK fertilizer had the highest stover yield at both sites. The means for green gram grain yield ranged from 0.22 t/ha to 0.07 t/ha and 1.07 t/ha to 0.11 t/ha for Nairobi Ndogo and Kairini farm, respectively. Overall, the study underscores the potential of integrated soil fertility management in enhancing sorghum and green gram production, ensuring food security, and improving soil health in Tharaka-Nithi County. The findings advocate for the adoption of conventional intercropping systems supplemented with appropriate fertilization strategies to optimize crop productivity and soil fertility management in similar agro-ecological contexts.