Jaiswal, A.K., Department of Plant Pathology and Weed Research, Institute of Plant Protection, Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, 50250, Israel, Department of Soil Chemistry, Plant Nutrition and Microbiology, Institute of Soil, Water and Environmental Sciences,The Volcani Center, Bet Dagan, 50250, Israel, Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P. O. Box 12, Rehovot 76100, Israel
Elad, Y., Department of Plant Pathology and Weed Research, Institute of Plant Protection, Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, 50250, Israel
Graber, E.R., Department of Soil Chemistry, Plant Nutrition and Microbiology, Institute of Soil, Water and Environmental Sciences,The Volcani Center, Bet Dagan, 50250, Israel
Frenkel, O., Department of Plant Pathology and Weed Research, Institute of Plant Protection, Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, 50250, Israel

The soil application of biochar, the solid carbon-rich product of biomass pyrolysis, may improve soil quality and crop productivity. Recently, soil applied biochar was found to reduce severity of foliar diseases and soilborne diseases in various crops. Biochar characteristics are expected to affect its disease suppression capability, as there is a profound variability in the physical and chemical properties of biochar depending on the initial feedstock and production parameters. The aim of this research was to explore the influence of biochar produced from different feedstocks and at different production temperatures on its ability to suppress the soilborne pathogen, Rhizoctonia solani, in cucumber (Cucumis sativus L.). Biochar prepared from two feedstocks (Eucalyptus wood (EUC) and Greenhouse waste (GHW)), each produced at 350 and 600°C were tested for their suppressive ability against damping-off at concentrations of 0-3%. In general, biochar addition at relatively lower concentrations enhanced plant growth performance and suppressed damping-off by R.solani. However, at higher concentrations, biochar was ineffective or even increased the disease incidence and severity as compared with the control, forming a U-shape response curve versus biochar concentration. Biochars produced at both low and high temperatures were equally effective against various disease parameters but suppression of disease was affected by the feedstock type. There was a significant interaction between feedstock and concentration for the final damping-off incidence and other disease parameters, indicating that each feedstock had an optimum concentration for disease control. The most effective dose for suppressing disease was 1% for EUC biochar and 0.5% for GHW biochar. In conclusion, R. solani suppression in cucumber induced by biochar soil amendment is feedstock and concentration dependent. © 2013 Elsevier Ltd.