Non-monotonic influence of biochar dose on bean seedling growth and susceptibility to Rhizoctonia solani: the “Shifted Rmax-Effect”

• DOI: 10.1007/s11104-014-2331-2
• Publication Date: 2014-11-21T11:36:49Z
• Authors: Amit K. Jaiswal; Omer Frenkel; Yigal Elad; Beni Lew; Ellen R. Graber
• Keywords: 2. Zero hunger; 0303 health sciences; 03 medical and health sciences

Aims Biochar affects the progress of plant diseases caused by soilborne pathogens, frequently featuring Ushapedbiochardose/diseaseresponsecurves.Thisstudy tested this phenomenon in common bean (Phaseolus vulgaris L.) with several biochars. Methods Four biochars prepared from two feedstocks (eucalyptus wood and greenhouse wastes) each at 350 and 600 °C were tested on bean seedling growth and infection causedbyRhizoctonia solaniatconcentrations of 0–3 % by weight. Biochar direct toxicity to R. solani was quantified in vitro. Results In general, lower concentrations (≤ 1% ) of biochar suppressed damping-off, whereas higher concentrations (3 %) were ineffective at disease protection. Plant growth in the absence of the pathogen was generally improved at all doses by the four biochars. Maximum growth response (G-Rmax) generally occurred at higher biochar doses than maximum disease reduction (D-Rmax). Direct toxicity to the pathogen could not explain disease reduction. Conclusion Inverted U-shaped biochar dose/plant growth and biochar dose/disease reduction curves are emerging as common patterns in biochar/crop/pathogen systems. Frequently, the inflection between growth promotion and suppression occurs at different doses than the inflection between disease suppression and promotion. We term this the “Shifted Rmax-Effect” .A s there is no simple rule-of-thumb for crop/soil/biochar/dose/ pathogen combinations, the possible effects of biochar on plant pathogens should not be overlooked.