Effects of Biochar on Saturated Water Holding Capacity of Red Clay and Plant Growth

Biochar is an environmentally friendly soil modifier due to its porous and high specific surface area. To investigate its impact on the water-holding capacity of red clay and the growth of common slope grass species, we selected red clay from Guilin as the research subject. Different types and dosages of biochar were incorporated into the red clay. Subsequently, water-holding capacity tests, pot-planting tests, and pH tests were conducted. Scanning electron microscopy (SEM) was employed to elucidate the mechanism by which biochar affects the water-holding capacity of red clay. Results revealed that the saturated water-holding capacity and pH value of red clay increased with the rising content of four types of biochar, effectively improving the environmental conditions for plant growth. Specifically, adding biochar increased the germination number and plant height of grass seeds. However, a biochar content exceeding 5% negatively affected the growth of grass seeds. Microscopic tests indicated that biochar filled the pores between red clay aggregates, thereby enhancing the saturated water-holding capacity of red clay thanks to its porosity and hydrophilicity.