Asian Journal of Environment & Ecology

The application of biochar as a soil amendment has recently gained attention due to its potential to improve soil fertility and crop productivity.  An experiment was carried out at Mkindo farmer-managed irrigation scheme in Mvomero District, Tanzania. This study evaluated the effect of different application rates of rice husk biochar on growth parameters and water productivity in irrigated paddy fields.  Four treatments—T1 (0 tons/ha), T2 (5 tons/ha), T3 (10 tons/ha), and T4 (15 tons/ha), each repeated three times in a complete randomized block design. The measured variables included plant height (PH), number of tillers (NT), number of leaves (NL), number of productive tillers (NPT), root depth, panicle length (PL), total biomass (TB), biomass and paddy yield, along with water productivity. The Data were subjected to the Least Significant Difference test at p<0.05. The findings revealed that paddy treated with T3 (10 tons/ha) considerably increased PH, NT, biomass, and grain production in both wet and dry seasons.  In the dry season, T3 produced 9.2 t/ha, while in the wet season produced 9.07 t/ha.  The rainy season's water productivity peaked at 0.91 kg/m³, whereas the dry season's was 0.80 kg/m³. Treatment T3 had the greatest economic water productivity, with 272.02 Tsh/m³ (dry) and 306.97 Tsh/m³ (wet).  While panicle length peaked in T1, root depth peaked in T4. Nevertheless, T4 showed declining benefits, suggesting that 10 tons/ha was the ideal amount to maximize output and economic efficiency.  These findings suggest that a moderate application rate of 10 tons/ha is optimal for improving paddy productivity, water efficiency, and economic returns from rice husk biochar treatment, demonstrating the utility of RHB as a soil supplement in irrigated rice systems.