Biochar has drawn significant attention as soil amendment, carbon fixer, and pollutant remediation. However, the significance of biochars aging regarding soil silicon contents with underlying interaction mechanisms in soil-rice ecosystem are not vivid. Herein, we report a rice pot experiment with Si-rich (RH300-700) and Si-deficient (WB300-700) biochars. The improvement in rice grain yield with Si-rich and Si-deficient biochar amendment could not relate to the silicon content of biochars. The RH300 increased the concentration of grain silicon in high-silicon soil (HSS), and the cumulative silicon uptake of rice grain with RH biochar amendment was increased by 10.33-26.23% and 57.59-61.48% in HSS and LSS (low-silicon soil), respectively. The silicon uptake of rice plant derived from soil silicon was decreased in presence of RH biochars, in both HSS and LSS environment, and thus led to cumulative rice silicon. The WB700 decreased the silicon concentration of rice grain and cumulative silicon uptake silicon of rice plant in LSS environment. The minerals of iron and silicon were found on surface of aged WB700, as observed from SEM-EDX. We propose that the minerals of iron and silicon in soil may be adsorbed onto the silicon surface of biochar, thereby preventing the silicon dissolution with minimum availability of silicon for soil. The aging process of biochar builds a reservoir for soil silicon on surface of biochar. Thus, a Si-rich biochar will result in slow release of Si and achieve a goal of biogeochemical cycling of soil silicon.

Effects of biochars on soil silicon cycle in a soil-rice ecosystem

256th National Meeting (2018)

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