The effect of biochar on plant diseases: what should we learn while designing biochar substrates?

The increasing demand for soilless substrates and rising environmental concerns about the use of non-renewable resources such as peat has led to the search for alternative constituents of growing mixtures for containerized plants. In this report we reviewed the works concerning biochar as constituent of growing media, targeting its influence on plant growth and plant disease. Biochar mostly has positive or neutral influences on plant growth compared with peat media when present in concentrations higher than 25% (v:v). However, studies of biochar influence on plant disease reveals that while lower concentrations (≤1%) of biochar often suppressed several diseases, higher concentrations (≥3%) were mostly ineffective or induced plant disease. For use as horticultural peat replacement, it is recommended that biochar feedstocks and concentrations be standardized and the potential effect of biochar on plant disease be considered, so that growers can rely on consistent and reproducible biochars for desired effects.