Characterization of different biochars and their impacts on infectivity of entomopathogenic nematode Heterorhabditis bacteriophora

Entomopathogenic nematodes (EPNs) are important biological control agents that are endoparasites of many types of insects. Improving soil health has potential to provide more suitable conditions and increase effectiveness of EPNs. For this purpose, effects of feedstock type (walnut shell, fir wood sawdust, rice husk, einkorn wheat husk and corn waste from field) and sand to biochar proportion (100:0; 90:10; 80:20 and 60:40 by weight) on infectivity of entomopathogenic nematode was investigated in this study. Based on characterization results, the selected biomass samples are suitable raw materials for the production of biochar by pyrolysis method. With regard to our results, except for walnut shell biochar, all biochar samples have significantly reduced EPN infection at 60:40 mixtures compared to control. Walnut shell biochar had no negative effect on EPNs and infection rate was 100% for all proportions. The macroporous structure of the walnut shell biochar contains moisture that can be adsorbed in the pores. When the oxygen contained in the air dissolved in adsorbed water, it was a source of life for EPNs that provided their oxygen demand from dissolved oxygen in water. However, application of corn waste biochar with high ash content was detrimental to EPN survival as a result of an increased salinity of the soil. The study concluded that biochar application may have detrimental or indifferent impacts on some beneficial nematode species.