Evolution of organic carbon components in saline–alkali soil after ten years of biochar application: implications of soil carbon sequestration capacity and stability of the soil carbon pool

Abstract

The long-term positioning test for biochar for saline–alkali land improvement was carried out for four treatments, CK (0%), and 20 (C1), 40 (C2) and 60 (C3) t ha⁻¹, to clarify the characteristics of the organic carbon components and the carbon sequestration potential. Compared to the control sample, the soil water holding capacity was significantly increased by 35.6–39.2% when biochar was applied. The average data from a ten-year field study demonstrated that biochar incorporation significantly increased the total soil organic carbon (TOC) by 11.2–54.4%. The amounts of dissolved organic carbon in the soil (DOC), easily oxidizable carbon (EOC), and mineral-bound organic carbon (MOC) were the highest in the 0–20 cm layer and then decreased with increasing soil depth with ranges of change of −11.3–61.8, 29.6–186.7 and −20.6–105.3%. In addition, the concentrations increased with increasing biochar addition rates, and the DOC, EOC, and MOC were significantly more positive than the TOC. In general, the ten-year application of biochar in saline–alkali soil considerably increased the soil organic carbon and carbon component content, which was conducive to improving the soil carbon sequestration capacity and the stability of the soil carbon pool. The biochar improved the saline–alkali soil with long term effects, which could increase soil carbon fixation and help emission reduction in the future.