Effect of coal char concentrations on soil bulk density and soil water-holding capacity

Coal char (CC) is a porous carbon material prepared from the pyrolysis of coal, which burns off the volatile matter of coal, leaving behind a high-carbon solid material. Adding porous material to the soil will directly affect the soil's physical properties. This study aimed to determine the effect of CC concentrations on soil bulk density (Db)and water-holding capacity (WHC) on sandy loam and sandy clay loam soils with CC concentrations of 0 (control), 2.5, 5, 10, 20, and 40% by soil weight (w/w) in a greenhouse pot experiment. Results indicate that soil Db is significantly different (p<0.01) in CC-treated soils compared to non-treated soil. Regression analysis results suggest that an increase in CC concentration reduced soil bulk density in both soils (Figure 2b), and there was a high correlation between the CC concentrations and soil Db with R2 values of 0.8171 and 0.9050 on sandy loam and sandy clay loam soils, respectively. Soil WHC on both soils was significantly different (p<0.01) after 5% CC treatments compared to the control treatment. There was a linear response between WHC and CC concentrations and a greater correlation between soil WHC and CC application rates with R2 values of 0.9871 and 0.9472 on sandy loam and sandy clay loam soils, respectively. Micro pores of CC can have contributed to higher water holding in both soils.