Dynamic effects of three kinds of shell biochars on physicochemical properties of red soil in South China

Objective  This study was to explore the dynamic effects of three kinds of shell biochars on the physical and chemical properties of red soil in southern China, and provide a theoretical basis for improvement of red soil in southern China.

Method  Three kinds of shell biochars were prepared by slow pyrolysis method and characterized. The dynamic effects of adding three kinds of shell biochars on soil organic matter content, bulk density, pH and available potassium were studied through indoor experiment.

Result  During the treatment period of 1–90 d, the application of pine nut shell biochar, rice husk biochar and camellia oleifera shell biochar significantly increased the contents of soil organic matter and available potassium. Compared with CK group, within 30–90 d, the content of organic matter increased by 258.94%–284.92% in 5% (w) pine husk biochar application treatment, and the content of available potassium increased by 429.98%–716.58% in 5% (w) rice husk biochar application treatment. During 1–90 d, the application of rice husk biochar decreased the bulk density of red soil, and within 30–90 d, the application of 5% (w) rice husk biochar decreased the bulk density of red soil by 9.72% –15.38% compared with CK group. During 1–90 d, the application of camellia shell biochar significantly increased soil pH , and within 30–90 d, the application of 5% (w) camellia shell biochar increased soil pH by 16.91%–29.53% compared with CK group. In addition, the effects of different application amounts of pine nut shell biochar on soil physical and chemical properties showed that the application of 8% (w) pine nut shell biochar could steadily increase soil organic matter content, pH and available potassium content, as well as decrease soil bulk density during the treatment period of 1–90 d.

Conclusion  Different shell-based biochar can all improve soil characteristics, increase soil organic matter and soil available potassium contents. The application of pine nut shell biochar may have a more significant effect on improving soil organic matter content, and the application of rice hull biochar may have a more significant effect on reducing soil bulk density and increasing available potassium content, and the application of camellia oleifera shell biochar may have a more significant effect on increasing soil pH.