Partial Replacement of Chemical Fertilizer by Biochar-Based Fertilizer Increases Rice Yield and Soil Quality

Substituting chemical fertilizers with organic fertilizers is a significant agricultural practice that can enhance crop yield while influencing soil activity. To investigate the effects of biochar-based organic fertilizer on rice yield, quality, and soil physicochemical properties and activity, this study conducted a field experiment with three treatments: chemical fertilizer only (CK), 30% of chemical nitrogen substituted with conventional organic fertilizer (CF), and 30% of chemical nitrogen substituted with biochar-based organic fertilizer (BF). Compared with chemical fertilizer alone (CK), both CF and BF treatments significantly increased rice yield by 8.9% and 14.2%, respectively, with BF showing a further increase over CF, primarily attributed to an 18.7% increase in panicle number. Both organic fertilizer treatments significantly improved grain quality, reducing amylose content by 4.6% and 13.1%, and increasing taste value by 3.3% and 3.6%, respectively. Dry matter accumulation throughout the growth period was significantly enhanced, with BF increasing total dry weight by 11.2% at maturity compared to CK. Root morphology was markedly improved, with BF increasing root volume by 146.1% at the grain-filling stage. Soil nutrient content was significantly elevated, showing maximum increases under BF of 118.9% for alkali-hydrolyzable nitrogen, 51.7% for ammonium nitrogen, 30.6% for available phosphorus, and 177.6% for available potassium. Soil enzyme activity analysis revealed significant enhancements in urease, acid phosphatase, and sucrase activities, with maximum increases of 91.5%, 105.6%, and 104.2%, respectively, under BF. These findings demonstrate that organic fertilizers, particularly biochar-based organic fertilizer, can synergistically enhance rice yield and quality by promoting root growth, strengthening soil microbial activity and enzymatic reactions, and optimizing nutrient supply. Biochar-based organic fertilizer exhibits significant advantages in improving soil biological fertility and maintaining stable nutrient supply during the late growth stages of rice.