Testing Biochar’s Ability to Moderate Extremely Acidic Soils in Tea-Growing Areas

Abstract

Biochar as a by-product of the carbonization of biomass has an inherent potential to modify acidic soils due to its alkaline nature. To explore the mechanism and effectiveness of biochar, a case study was conducted on severely acidic soils from six fields under tea cultivation in a subtropical zone, comparing rice husk biochars, in three rates (B5, B10, B15 t ha−1), and CaCO3 as conventional liming practice. The results showed increases in pH of 71.5%, 52.7%, 30.6%, and 29.7% in B15, B10, B5, and CaCO3-treated soils compared to the control. On average, B15 and B10 treatments resulted in the highest organic matter with 12.3% and 9.7%, respectively. B15, B10, B5, and CaCO3 caused increases of 196.6%, 173.4%, 129.7%, and 100.9% in base saturation compared to the control, respectively. Also, after the application of B15, B10, and B5 treatments, the effective cation exchange capacity increased by 191.4%, 112.1%, and 39.5%; however, the application of CaCO3 resulted in a 20.1% decrease. Overall, applying biochar on acidic soils provides adequate negative charges due to its well-extended specific surface area and pore volume, which cause the absorption of additional Al+, resulting in ameliorating soil pH. The application of proper biochar could notably be more effective in improving acidic soils than conventional practices such as the overuse of CaCO3. In this regard, evaluating various biochars in terms of feedstock, pyrolysis conditions, and modification scenarios merits in-depth research in future studies.