Interaction Effect of NPK Fertilizer and Rice Husk Biochar on Growth and Yield of Paddy Rice

Rice (Oryza sativa L.) is the third most preferred cereal, after maize and wheat in Kenya. Continuous monocropping in Ahero paddy rice fields without fertilizer application and soil amendment reduces yield. This study determined the effects of combining NPK fertilizer and rice husk biochar on the growth and yield of paddy rice. The treatments were rice husk biochar B0, B5, B10, and B15 (t ha-1 ) and NPK (F0, F100, F200, and F300 (kg ha-1 ). The study was conducted between May 2024 and January 2025 over two seasons. Three-replications in split-plot Randomized Complete Block Design (RCBD) was used. Tiller number, above-ground biomass, plant height, 1000-grain weight, and yield were measured. ANOVA was performed using R software version 4.4.2, and Fisher's LSD employed to differentiate the mean at p<0.05. NPK and biochar combination increased rice tillering by 53%–85%. Above-ground biomass increased by 47.1%–130.6% over control. NPK at 200 kg ha-1 and biochar 15 t ha-1 increased 1000-grain weight from 11.6% to 12.1% and grain yield 69.2% over the control. However, biochar and NPK fertilizer above 200 kg ha-1 tends to lower grain yield and weight. The results imply that Ahero paddy rice production may be managed well with moderate NPK and biochar rates.