Abstract:The effects of biochar which was made of crop straw on physical properties of meadow black soil and dynamic changes of soil water after individual rainfall were studied. The experiments were conducted by field pilots which were located at the sloping farm-land with three degrees of land slope gradient of Hongxing State Farm, Heilongjiang Province in 2015, and soybean, the main crop type of study area, was selected as experimental crop. Five levels of biochar were set, as 0t/hm, 25t/hm, 50t/hm, 75t/hm and 100t/hm of biochar were put in the field pilots, which were represented by CK, C1, C2, C3 and C4, respectively. During the whole growth period of soybean, the soil physicochemical properties were investigated, including soil water characteristic curve, soil water diffusivity, soil bulk density, rate of soil porosity, organic matter content of soil, saturated soil water content, field water capacity and characteristics of soil water after individual rainfall. Soil water characteristic curve was measured by centrifuge, soil water diffusivity was tested by horizontal vitreous soil column, and soil water contents were measured by TDR field soil water measurement system in situ. The results showed that biochar could remarkably reduce soil bulk density and decrease soil water diffusivity of meadow black soil in the black soil area. The residual soil water content could be declined by 27.6% by treatment of C4. With the increase of biochar quantitative level, soil water diffusivities of C1, C2, C3 and C4 were decreased by 34.8%, 37.5%, 71.4% and 58.9%, respectively. Additionally, it could give a rise to the saturated soil water content, field capacity and soybean yield, and the treatment with 75t/hm biochar got the highest yield. During an individual rainfall, with the use of biochar, the variation amplitude of soil water content tended to fall. This helped to accelerate the process of soil water content changing from rapid declining stage to slow declining stage, meanwhile, it increased the soil water content in the slow declining stage obviously. The research results can provide theoretical foundation for efficient utilization and protection of soil and water resources in agriculture in the black soil region.
