Biochar as a Sustainable Soil Amendment: Enhancing Soil Fertility, Carbon Sequestration, and Crop Productivity Under Changing Climatic Conditions

Abstract

We evaluated the efficacy of biochar as a soil amendment for improving soil fertility and crop productivity under variable climatic conditions. A field-based experimental design was employed across 16 agricultural research farms in diverse agroecological regions, with 320 plots arranged in a randomized complete block design. Eight biochar treatments, including rates of 5, 10, and 20 t ha⁻¹ and combinations with integrated nutrient management, conservation tillage, drip irrigation, and crop residue retention, were replicated three times over three consecutive cropping seasons. Data collection included continuous field observations, soil sampling, and laboratory analyses of physicochemical and biological parameters. Statistical analyses comprised ANOVA, Tukey’s HSD test, Pearson correlation, multiple linear regression, and principal component analysis. Biochar application significantly improved soil quality and crop productivity. Specifically, soil organic carbon increased by 31.6%, water-holding capacity improved by 26.8%, available nitrogen, phosphorus, and potassium increased by 24.9%, microbial biomass carbon rose by 28.2%, and grain yield increased by 25.7%. Agricultural sustainability outcomes showed improvements of 27.9% in soil fertility, 23.8% in water-use efficiency, and 29.4% in carbon sequestration. Multiple linear regression identified soil organic carbon (standardized β = 0.49, p < 0.001), biochar application rate (β = 0.43, p < 0.001), water-holding capacity (β = 0.36, p < 0.001), and nutrient availability (β = 0.31, p = 0.002) as significant predictors, explaining 78.4% of the variance in crop productivity. A strong positive correlation was observed between the Soil Carbon Sequestration Index and crop productivity (r = 0.86, p < 0.001). Principal component analysis identified three components explaining 84.2% of total variance, representing soil carbon accumulation, water retention, and crop productivity.