Effects of Biochar and/or Oyster Shell Powder Applications in Regulating Carbon Pool and Mineral Preservation of Acidified Tea Plantation Soil

Objective Effects of applying biochar and/or oyster shell powder at tea plantations on the regulations of soil carbon pool and mineral preservation were studied for improved carbon sequestration and ameliorated acidification in the soil.

Method At acidified red soil tea plantations in Fujian Province, a field experimentation was conducted applying no treatments as control (CK) and addition of oyster shell powder at a rate of 100, 200, or 300 kg·hm⁻², biochar at a rate of 7.5 or 15 t·hm⁻², or the combined use of both oyster shell powder (50 kg·hm⁻²) and biochar (7.5 t·hm⁻²). Total carbon (TC), organic carbon (OC), labile carbon fractions, calcium-bound OC, and iron-aluminum-bound OC in the soil at the test sites were measured. Correlation between the various treatments and soil conditions was determined.

Result The treatments significantly increased TC and OC in soil over CK. By using both oyster shell powder and biochar, TC and OC rose by 137.4% and 119.1%, respectively, which were significantly higher than the use of single additive at low dosage. All treatments significantly raised the dissolved OC (DOC) and readily oxidizable carbon (ROC) and reduced the iron-aluminum-bound OC in varying degrees. Total OC significantly correlated with DOC, ROC, and calcium-bound OC but inversely with exchangeable aluminum.

Conclusion Although applying oyster shell powder or biochar alone significantly enhanced the carbon pool, the combined use of both soil modifiers even at low levels would synergistically further the improvement on soil. An elevated calcium-bound OC induced by the combination significantly stimulated the mechanism that preserves the mineral and promotes stable OC sequestration.