Application of biochar for soil biological improvement

Soil biological properties play a critical role in determining the environmental functions and processes of agricultural ecosystems. This chapter provides a comprehensive review of the recent research findings on biochar amendments influencing soil biological properties and ecosystem services. In general, biochar ameliorated soil biological properties and soil ecological functions, but the effect varied with the soil type, the biochar quality, and the application rate. Addition of biochar stimulated soil enzymatic activity and microbial biomass, especially for acidic or contaminated soils. Soil respiration was also primed, to a greater extent by biochars containing more labile carbon as those produced at lower pyrolysis temperatures. Biochar amendment further improved the mycorrhizal colonization of plant roots, the abundance of bacteria and viruses in soil, and the microbial community stability. Biochar also mediated plant systemic resistance against foliar diseases and inhibited plant parasitic nematodes in soils. Earthworms and arthropods can ingest biochar particles for the inherent labile C or the bacteria/fungal mycelia sorbed on the surface, but the soil fauna might be restricted at high biochar application rates due to the substantial soil alterations in pH and other physiochemical conditions. The effects of biochar amendment on soil biological properties could be transient or of long term, likely through altering soil physical (e.g., soil structure, aeration, water retention, temperature, and microbial habitat) and chemical (e.g., pH, nutrient availability, contaminant detoxification) properties and providing additional nutrients and labile carbon. Intensive research with long-term field trials is warranted to understand the mechanisms and processes through which biochar interacts with soil biological communities.