ORIGINAL ARTICLE Potential of anaerobic digestate of dairy manure in suppressing soil‐borne plant disease Zhifei Pan 1 | Guangdou Qi 1 | Fetra J. Andriamanohiarisoamanana 1 | Takaki Yamashiro 1 | Masahiro Iwasaki 1 | Takehiro Nishida 1 | Suchon Tangtaweewipat 2 | Kazutaka Umetsu 1 1 Department of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan 2 Department of Animal and Aquatic Sciences, Faculty of Agriculture, Chiang Mai University, Chiang Mai, Thailand Correspondence Kazutaka Umetsu, Department of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan. Email: umetsu@obihiro.ac.jp Abstract Frequent use of pesticides to control soil‐borne plant disease leads to environmental pollution and the development of pesticide resistance in phytopathogens. Soil amendment is considered to have the potential of suppressing plant disease because of its biological properties. However, information on anaerobic digestate is limited. In this study, potential of antagonistic activities of anaerobic digestate against phy- topathogens were investigated by detecting the amounts of antagonistic bacteria (Bacillus and Pseudomonas) in anaerobic digestates of dairy manure. The results showed that anaerobic digestion increased the total amounts of Bacillus and Pseu- domonas in digestate. Bacillus suppressed growth of phytopathogens, while Pseu- domonas did not show any antagonistic activities. These results indicated that Bacillus was an effective antagonistic bacterium in digestate against phytopathogens. Furthermore, two selected isolates, B11 (Bacillus subtilis) and B59 (Bacillus licheni- formis), were applied in field experiments and showed significant reduction in percent infection of potato late blight (Phytophthora infestans). These results demon- strate the benefits of digestate in suppressing soil‐borne plant diseases caused by antagonistic bacteria. KEYWORDS anaerobic digestate, antagonistic bacteria, phytopathogen, Phytophthora infestans, soil-borne plant disease 1 | INTRODUCTION Anaerobic digestion is considered a sustainable and environmentally friendly process that treats organic wastes such as livestock manure. In addition to biogas production, this process also provides a liquid residue called anaerobic digestate (Holm‐Nielsen, Al Seadi, & Oleskowicz‐Popiel, 2009). Anaerobic digestate is considered a valu- able bio‐fertilizer because it consists of partially degraded organic matter (OM), microbial biomass, and inorganic compounds (Albur- querque et al., 2012). Not only does it provide a source of available nutrients (nitrogen and phosphorus) to plants but it also has positive effects on soil biological properties, such as microbial biomass and enzyme activities (Risberg, Cederlund, Pell, Arthurson, & Schnürer, 2017). Fungi infection is one of the major factors that cause plant dis- eases in agricultural fields. Pesticides are commonly used to control the diseases; however, frequent use of pesticides may lead to envi- ronmental pollution and the development of pesticide resistance in fungi (Mehta, Palni, Franke‐Whittle, & Sharma, 2014). In recent years, several studies have reported the suppressive effects of organic soil amendment, such as compost on soil‐borne plant dis- eases (Termorshuizen et al., 2006). Both anaerobic digestate and compost are organic amendments that include an available form of plant nutrients (N, P, and K), organic carbon, and abundant microbial Received: 8 May 2018 | Revised: 19 June 2018 | Accepted: 5 July 2018 DOI: 10.1111/asj.13092 Anim Sci J. 2018;1–7. wileyonlinelibrary.com/journal/asj © 2018 Japanese Society of Animal Science | 1