Effects of silicon (silicic acid)-enriched biochar amendments on emissions of methane and nitrous oxide from paddy soils

Although both biochar and silicon amendments have been shown to reduce greenhouse gas (GHGs) emissions from soil, their effectiveness in doing so has yielded varying results. Negative, positive and neutral responses have been reported. Combining both amendments into a silicon-enriched biochar may lead to optimum abatement of GHGs emissions from the soil. The current study was hence, conducted to evaluate the methane (CH₄) and nitrous oxide (N₂O) attenuation potentials of the silicon-enriched biochar amendments. The study was conducted via a pot experiment and the treatments included, the control (NPK only), post-pyrolysis silicon-enriched biochar (SiBC 1), pre-pyrolysis silicon-enriched biochar (SiBC 2), non-modified biochar (PrBC) and silicon (Si). All treatments received NPK at recommended rates. The biochars were characterised with the scanning electron microscope (SEM) and Fourier transform infrared spectroscope (FT-IR). In comparison to the control, PrBC, SiBC 1 and SiBC 2 reduced CH₄ emissions by 9.32 %, 41.06 % and 40.35 %, respectively while Si increased the emissions by 20.45 %. PrBC, SiBC 1, SiBC 2 and Si amendments reduced N₂O emissions by 20.55 %, 54.79 %, 57.53 % and 39.73 %, respectively as compared to the control. The instrumental analysis revealed that silicon enrichment enhanced biochar's surface properties e.g. porosity and surface reactive functional groups which might have contributed to the enhanced potential of the biochar to lower CH₄ and N₂O emissions through increased aeration and adsorption of nitrogen. Therefore, enriching biochar with orthosilicic acid is a novel method of optimising the attenuation of CH₄ and N₂O emissions from paddy soils.