Basalt powder amendment enhances carbon sequestration of paddy soil and increases rice yield

Based on the principle of enhanced rock weathering (ERW), as well as applying basalt powder to agricultural soil can sequester atmospheric CO₂ while providing essential mineral elements that promote crop growth. A pot experiment was conducted to investigate the effects of basalt powder application (at rates of 0.5%, 1.0% and 1.5% of soil mass) on soil inorganic carbon (SIC) content and rice growth in an acidic red paddy soil (pH≈5.1). The results indicated that:(1) Basalt powder application significantly increased SIC content (P<0.05). The high-rate group (B_1.5%) achieved a 20.3% increase in SIC. The weathering ratio of the basalt powder reached 21.3%, which was equivalent to a theoretical sequestration CO₂ fixation amount of 4.72 t·hm⁻² per rice season. (2) Basalt powder significantly raised soil pH and electrical conductivity (EC). The B_1.5% group increased pH by 0.46 and EC by 34.4%, while soil exchangeable acidity decreased significantly by 92.6%(P<0.05) . Correlation analysis revealed a strong linear positive correlation between application rates and pH/EC (R=0.9646 and 0.9512, respectively), and a strong negative correlation with exchangeable acidity (R=−0.9639). (3) Basalt powder substantially enhanced available silicon content in the soil, with 3.19, 5.79 and 7.60 times more in the B_0.5%, B_1.0% and B_1.5% groups, respectively (R=0.9926). This facilitated silicon accumulation in rice stems, leaves, and husks, which enhanced tillering capacity. Consequently, the B_1.5% group showed significant increases in effective tiller number (41.2%) and grain yield per plant (42.1%). This study demonstrates that basalt powder application serves as a multi-functional strategy for acidic paddy soils. It achieves substantial carbon sequestration through enhanced weathering, effectively mitigates soil acidity, and boosts rice productivity via the sustained release of available silicon and other minerals.