Biochars reduce infection rates of the root-lesion nematode Pratylenchus penetrans and associated biomass loss in carrot

Biochars, in addition to carbon sequestration, soil amelioration and improvement of plant performance, can measurably reduce disease severity of different pathogen types and even induce system wide defense responses in host plants. The aim of this study was to further investigate if biochars can provide resistance-enhancing effects to host plants faced with plant parasitic nematodes. We asked if these carbonized materials, as a result, may hold the potential to be used as an effective supplement for chemical nematicides. Four different biochars and zeolite (5% v/v) were tested on a carrot (Daucus carota) and root-lesion nematode (Pratylenchus penetrans) pathogen system. Plant biomass, nematode abundances in soil and root tissue (infection rate), as well as plant-nutrient status were quantified. P. penetrans caused decreased shoot- and fine root biomass in infected plants. All applied materials, except for the pine wood biochar, significantly reduced tap root infection rates of P. penetrans by approximately 80% and spelt husk biochar actually reduced infection rates by more than 96%. Infected plants of these treatments produced two to four times more plant biomass than infected plants of the non-material application treatment. It turned out that biochars produced from different feedstocks affected nematode infection rates and host plant biomasses quite differently. Induced resistance is a possible explanation for the highly reduced infection rates, as direct toxic effects of the biochar and effects of altered pH, water holding capacity, soil structure and plant nutrient status could be largely excluded. (C) 2015 Elsevier Ltd. All rights reserved.