Effect of Biochar Mixed With Different Phosphorus Rates on Selected Soil Chemical Properties in Western Kenya

Abstract

Low maize productivity in Acrisols and Ferralsols caused by phosphorus (P) fixation poses a constraint to food security in Bungoma County, Kenya. Continuous application of ammonia-based fertilizers has further intensified soil acidification, leading to declining soil productivity. This study evaluated the effect of biochar combined with different P fertilizer rates on selected soil chemical properties and maize performance. Field experiments were conducted during the long and short rainy seasons of 2023 at Kibabii (Acrisols) and Chwele (Ferralsols). A split-plot design with three replicates was used, where biochar sources formed the main plots and P fertilizer rates constituted the subplots. Biochar was applied at 5 t ha-1 at planting, together with three P rates (0, 13, and 26 kg P ha-1). Nitrogen fertilizer was applied at 75 kg N ha-1 in split applications. Maize hybrid H513 (Kenya Seed Company) was planted at a spacing of 75 × 25 cm. Soil chemical properties including pH, total nitrogen, soil organic carbon (SOC), and available phosphorus were analyzed. Data were subjected to analysis of variance (ANOVA) using GenStat (14th edition, 2012), and treatment means were separated using the Least Significant Difference (LSD) test. The interaction between biochar and P rate was not significant (p ≤ 0.413), indicating no synergistic influence on maize yield. Correlation analysis between soil chemical properties and grain yield showed a positive relationship with available P (r = 0.5169) and negative relationships with soil pH (r = –0.3340) and SOC (r = –0.1132).