Physicochemical Improvements in Sandy Soils through the Valorization of Biomass into Biochar

Abstract

Forestry management operations that are designed to prevent wildfires while also protecting the environmental compartments that are directly affected by them, such as soil, are of major relevance. The valorization of residual forestry biomass into biochar that is then used to be turned back into forest soils is an approach that meets Circular Economy principles. However, the effects on soil of the application of biochar that is produced from low-grade forestry biomass are unknown. In this work, a soil incubation assay was performed with a sandy soil that was amended with biochar produced from residual forestry biomass (Acacia) to assess its effectiveness in terms of boosting soil quality. The factorial study comprised the effects of biochar at two pyrolysis temperatures (450 °C and 550 °C), four application rates (0%, 3%, 6%, and 10% (w/w)), and three particle size classes (S < 0.5 mm, M = [0.5; 3.15], and L > 3.15 mm). The soil pH increased for all treatments to suitable agronomic values (5–7), and the water-holding capacity increased by 69% to 325% when compared to the control soil. The bioavailability of the plant nutrient elements also increased with the application rate, especially for treatments with small particles of biochar. Biochar that is made of low-grade biomass from forestry maintenance operations can be efficiently recycled back into forest soils to improve the physicochemical properties of agronomic relevance, thus allowing for a reduced water demand and better soil quality. However, studies on biochar applications in different soils are needed in order to assess the effectiveness of this approach.