Abstract
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.
Highlights
The shifted dose response between plant growth and disease responseJaiswal et al (2015) noted that is plant resistance to disease frequently biochar-concentration-dependent, and that in many instances, an unwanted effect on plant growth and biomass occurred at relatively higher biochar doses (Rondon et al 2007; Rajkovich et al 2012; Spokas et al 2012)
M.; Cepurnieks, G.; bioremediation trial using biostimulation, phytoremediation and bioaugmentation, Journal of Environmental Engineering and Landscape
Of studies have shown no effect of biochar on crop yields (Jeffery et al 2011; Ruysschaert et al 2016), and some have shown that biochar additions to soil can have unwanted effects on crop productivity, often due to tying up of nitrogen (Kammann et al 2015; Haider et al 2016), in clay-rich fertile soils
Summary
Jaiswal et al (2015) noted that is plant resistance to disease frequently biochar-concentration-dependent, and that in many instances, an unwanted effect on plant growth and biomass occurred at relatively higher biochar doses (Rondon et al 2007; Rajkovich et al 2012; Spokas et al 2012). The shifted Rmax paradigm could resolve apparent contradictions between Viger et al (2014) and an earlier report by Meller Harel et al (2012), which showed improved strawberry plant growth, decreased disease susceptibility, and up-regulation of defense-related genes in systems at relatively lower biochar doses (1 and 3 wt %; (Meller Harel et al 2012) These examples may all be related to wide range of materials that stimulate positive effects at low concentrations but cause toxicity and inhibition at higher doses (hormesis effect) (Jaiswal et al 2014; Kammann, Graber 2015). This possibility should be tested as one hypothesis for why foliar pathogens seem to be less sensitive to higher biochar concentrations than soilborne pathogens
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