Effects of Biochar under Different Preparation Conditions on the Growth of Capsicum

Biochar return to the field has been widely explored, but there is a problematic disconnect between biochar preparation and biochar return to the field. In this study, soybean straw is used as a raw material and is sieved into two components: 60-mesh (0.250 mm) and 110-mesh (0.130 mm). Four kinds of biochar were obtained by pyrolysis under the condition of no heat preservation and heat preservation for 60 min. The biochar was applied to the soil, and the effects of biochar on soil and capsicum growth were analyzed by Spearman correlation. Compared with the control group, soil pH, soil electrical conductivity, and soil organic matter decomposition were increased by 0.58, 101 μs/cm, and 9.48%, respectively. The fruit quantity, plant height, water, fat, soluble solid, and titrable acidity of capsicum were increased by 1, 0.55, 0.08, 0.62, 0.67, and 0.7 times, respectively. Spearman correlation analysis showed that soil properties and capsicum growth were most affected by biochar’s specific surface area (SSA). Therefore, increasing the biomass mesh number and heat preservation time is beneficial to increasing the SSA of biochar and facilitating the return of biochar to the field and the best preparation conditions are 110-mesh soybean straw biomass pyrolysis and heat preservation for 60 min.