Specified Dosages of Biochar Application Not Impact Native Organic Carbon but Promote a Positive Effect on Native Humic Acid in Humicryepts Soil

Abstract

Biochar is considered to have potential use in carbon (C) sequestration and has been widely used in soil amendment. Humic substances (HSs), assigned as the stable organic C, have obvious agronomic benefits. However, the response mechanisms of these carbonaceous substances to biochar are unclear in biochar-amended soils. In a two-year experiment, the δ13C technique was employed to trace the fate of the biochar-derived C in HSs and evaluate the effects of four treatments, including no biochar control (CK) and biochar addition at dosages of 6 t ha−1 (BC6), 12 t ha−1 (BC12), and 24 t ha−1 soil (BC24), on soil organic carbon (SOC) and HSs. Compared to CK, biochar application significantly improved total SOC contents and the C pool index, whereas the C labile index declined. Humic acid (HA) and humin were distinctly enhanced in bulk soil. Moreover, the aliphaticity was intensified in the chemical composition of HA. In particular, native HA contents substantially increased by 16.30–55.95%. Biochar-applied C of 4.08–6.43% was finitely involved in HA formation over the two years, which resulted in a genetic relationship between soil HA and biochar to some extent. The low dosages of biochar at 6 t ha−1, 12 t ha−1 and 24 t ha−1 did not obviously affect native SOC contents. Moreover, BC24 had less of an effect on HA formation compared to BC6 and BC12, but had the highest SOC. These results demonstrate that biochar application can improve SOC stocks, reduce C instability and promote HSs formation, and they suggest that determining and keeping an optimum dosage of biochar application can represent an effective strategy (i.e., not only sequestrate C, but also improve soil quality), which is beneficial to sustainability in the ecological environment and agriculture.

Carbon-enriched organic amendments differently affect the soil chemical, biological properties and plant biomass in a cultivation time-dependent manner

“…The increase in TC values between 12 and 24th week of experiment was 10%, suggesting carbon sequestration ability of applied amendments. Similar ability of biochar (24 t ha −1 ) to improve SOC stocks and improve C stability was reported by Li et al [42].…”

Large-Scale Biochar Incorporation Does Not Necessarily Promote the Carbon Sink of Estuarine Wetland Soil

“…Numerous studies on the effects of straw biochar incorporation into soils have revealed soil quality improvement, a reduction in greenhouse gas emissions and plant growth promotion [3][4][5][6]. For CO 2 sequestration, it is generally accepted that biochar application is beneficial to the C sink in most categories of soil [7,8]. Owing to its chemical and biological inertness, as well as the physical protection of its surrounding environment, straw biochar trapped 47% of soil organic carbon (SOC) in rice cultivation soil and 57% in maize cultivation soil [9].…”