Investigation on structure, evaporation, and desiccation cracking of soil with straw biochar

Abstract

To investigate the cracking behavior in the evaporation process of the soil surface with biochar as an additive, five experimental groups were established in the natural environment with 0, 12, 60, 120, and 170 g·kg⁻¹ biochar. The results of an investigation on organic matter and aggregations indicate that a high content of biochar can significantly improve the content of organic matter and the amount of soil aggregates. After adding 60 and 170 g·kg⁻¹ biochar, the content of organic matter increased by 19.47% and 84.12%, respectively, and the content of soil aggregates with an average diameter greater than 0.25 mm increased by 16.43% and 38.20%, respectively. The investigation also examines the evaporation and cracking characteristics of soils that contain biochar. The rate of evaporation is approximately a “step” type function with time. The rate of evaporation is observed in three stages: the rapid, decelerating, and final evaporation stages. In the rapid evaporation stage, the initial evaporation rate of the sample that contains biochar is increased on average by 46%. The fractal dimension and cracks rate are decreased by 22.95% and 20.99% with 120 g·kg⁻¹ biochar addition. This means that the increase of soil organic matter after adding biochar plays a crucial role in the stability of aggregates. As a soil conditioner, biochar has the ability to enhance soil water retention capacity and is a sustainable strategy to improve soil properties.