Effect Of Biochar On Porperties And Carbon Cyale Of Limestone Soil

Biochar refers to carbon concentration under pyrogenation of biomass on the condition of anoxic or anaerobic environment, which already has extensive research in recent years in soil amendment, carbon sequestration, and restoration of environment pollution, etc. A field pot experiment was conducted with the research subjects of brown and red limestone soil to study the effect of biochar on the inprovement of the brown and red limestone soil, growth of maize and soybean, and migration and transformation of carbon in the brown limestone soil system, respectively. In this experiment, biochar is produced by the original material of bagasse, which made in a self-made carbonized oven. The main results of the study are as follows:(1) Effect of biochar on soil characteristics. Both the properties of brownand red limestone soil are influenced by biochar, but the influence of results are different. There are no obvious effects of biochar on the soil pH, available N, total P and Kof both limestone soils, respectively. Soil bulk density and biochar concentration have a negative correlation, while TOC and C/N had positive correlation with biochar. Biochar increase the contents of total N, available P and K of both limestone soils. There is no significant influence of biochar on the CEC of brown limestone soil, while it increases that of red limestone soil. Biochar reduced the GMD of brown limestone soil, but there is no significant effect on the GMD of red limestone soil. The moisture of brown limestone soil is increased first and then decreased along with increasing of biochar concentration however, the moisture of red limestone soil is increased with increasing of biochar concentration.(2) Effect of biochar on crop growth. Biochar increase the biomass and crop yield of maize and soybean in both limestone soils. Biochar with high concentration (2%and5%) can increase the biomass and maize yield significantly in brown limestone soil, while biochar with low concentration (0.5%) and high concentration (2%) can both increase that in red limestone soil. The biomass and yield of soybean in both limestone soils can be increased by biochar with both low and high concentration.(3) Effect of biochar on the migration and transformation of carbon in limestone system, biochar have an effect on the soil CO2concentration and emission rate of brown limestone soil, and the results affected by the growth period of maize. In the stage of maize seedling, the soil CO2concentration in0-30cm depth and CO2emission rate are significantly increased when the concentration of biochar up to5%. In the jointing stage, heading stage and maturity stage of maize, soil CO2concentration of0-30cm depth and CO2emission rate are significantly increased with biochar concentration of2%and 5%. The concentration of Ca2+and HCO3-in leaching water of soil are increased by biochar with concentration of2%and5%after the jointing stage of maize, which increase the rate of karstification.In sum, biochar can improve the properties of brown and red limestone soil in karst mountainous area in some extent, and the improvement effect on red limestone soil is better than brown limestone soil. Moreover the growth of maize and soybean in both limestone soils are improved by biochar, and the promoter action in soybean is better than in maize.The rate of migration and transformation of carbon in soil system is increased after the jointing stage of maize when the biochar with the concentration of2%is adde in brown limestone.