EFFECTS OF NPK FERTILIZER AND RICE HUSK BIOCHAR APPLICATION ON GROWTH AND YIELD OF PADDY RICE (Oryzae sativa L) IN AHERO, KENYA

Abstract

Over one billion people around the globe depend on rice (Oryza sativa L.) to meet their dietary requirements. In Kenya, rice ranks as the fourth staple food, following maize, beans, and potatoes. Despite its importance, rice production in Kenya is limited by numerous factors like pests and diseases, water availability and irrigation infrastructure, land tenure and fragmentation, limited access to credit and financing, climate change and environmental degradation as well as policy and institutional problems. Ahero paddy rice farmers suffer low rice yield due to low soil fertility, expensive farm resources, scarce certified seeds, as well as unreliable water supply that results in low yield relative to demand. On the other hand, overuse of land without fertilizer and soil amendment causes nitrogen depletion and low rice productivity. The objectives of this study were: i) To determine the effects of NPK fertilizer (17:17:17) and rice husk biochar on growth and yield of paddy rice, ii) To determine the effects of combining biochar and NPK on growth and yield of paddy rice, iii) To determine the residual effects of rice husk biochar on selected nutrient uptake (N, P, K) and yield of paddy rice. The study was conducted at Ahero farmers’ paddy rice fields in Kenya from May to September 2024 and September to January 2025. The treatments were NPK fertilizer (0, 100, 200, and 300 kg NPK ha-1) and rice husk biochar (0, 5, 10, and 15 t ha-1). A Randomize Complete Block Design (RCBD) with three replications in a split plot layout was used for the experiment. Growth data taken included tiller number at 30 and 60 days after transplanting, plant height, whereas yield data included above-ground biomass, panicle length, number of spikelets, grains per spikelet, panicle harvest index, 1000 grain weight, and grain yield. R software version 4.4.2 was used for data analysis, utilizing General Linear Model (GLM) for ANOVA and Fisher's Least Significant Difference at P≤0.05 for means separation. NPK fertilizer increased rice tillering and grain yield between 21.9% to 33.2% and 30.1% to 42.7% respectively related to no fertilizer control. For the combination of NPK and biochar, 200 kg NPK ha-1 and 15 t biochar ha-1 produced more yield from 69.2% to 138.4%. Rice husk biochar applied in the first season showed some residual effects on the crop growth and yield by 16.0% to 32.4% and 17.5% to 31.4% respectively compared to the control. Biochar treated plots had high N, P and K uptakes of 63.8%, 75.0% and 52.2% respectively. Comparatively, NPK fertilizer rate greater than 200 kg ha-1 reduced grain yield. Residual rice husk biochar increased growth and yield corresponding to increased biochar rates.