Biochar application for the improvement of water-soil environments and carbon emissions under freeze-thaw conditions: An in-situ field trial

摘要

There are few studies about biochar application in seasonally frozen soil areas. The regulatory mechanism of biochar on the water-soil environment and carbon emissions in seasonally frozen soil areas is unclear, which affects the study of nutrient migration and spring cropping systems under the control of biochar. For this purpose, we monitored the soil temperature (Ts), soil liquid moisture content (Ms) and soil respiration (Rs) rate during the freeze-thaw period under different application amounts of corn stover biochar (0 t·ha~(-1), 15 t·ha~(-1), 30 t·ha~(-1), 45 t·ha~(-1) and 60 t·ha~(-1)). The results showed that biochar can reduce the thermal conductivity of soil, thus improving the thermal insulation effect of frozen thawed soil, and Ts increased by 1.8-5.7 °C. The Ts and Ms were more sensitive to the high biochar application amount than to the low application amount At the same time, biochar changed the soil aggregate distribution, and Pearson correlation analysis indicated that the soil water retention capacity increased by increasing the macroaggregate content (＞0.25 mm), and the Ms increased by 3.7-6.1%. Principal component regression (PCR) analysis showed that biochar can promote soil carbon emission, and Rs of soil treated with biochar was 0.01-0.58 μmol m~(-2) s~(-1) higher than that of the control. The Ms and Ts were the most important factors promoting the carbon emissions of freeze-thaw soil under the synergistic effect of biochar and freeze-thaw conditions. However, biochar may promote soil CO_2 emissions by affecting the water-soil environment. Considering the soil moisture, seed germination and growth conditions in spring, the suitable biochar application amount was determined to be 44-51 t·ha~(-1). This study provides theoretical support for determining reasonable and effective biochar control measures and improving the soil productivity of farmland soil in seasonally frozen soil areas.