Applying Awamori Distillery waste for biological soil disinfestation on Shimajiri Mahji soil in Miyako Island, Okinawa, Japan: Identifying the indigenous Fusarium pathogen of green okra

Abstract

Miyako Island is a major vegetable-producing region in Okinawa Prefecture, but soilborne diseases such as Fusarium wilt are prevalent, necessitating effective soil treatmnent measures. Biological soil disinfestation (BSD) is regarded as an effective alternative to chemical soil fumigation for managing these diseases. Awamori distillery waste—the residue produced after fermenting indica rice—is generated locally during liquor production and may serve as an effective material for BSD. This study evaluated the use of Awamori waste in the BSD treatment of Shimajiri Mahji soil on Miyako Island by monitoring changes in the oxidation-reduction potential (ORP), pathogen bud cells, crop yield. In laboratory experiments, BSD treatment with Awamori waste containing > 0.05 wt% carbon reduced Fusarium nirenbergiae to undetectable levels when the soil redox potential dropped below − 200 mV. In glasshouse experiments, BSD treatment with Awamori waste containing 0.2 wt% carbon similarly decreased F. nirenbergiae to undetectable levels. Furthermore, the marketable yield of green okra cultivated after BSD with Awamori waste was significantly higher than the yield cultivated after BSD with ECOLOGA ~ L^®. In the field trial, BSD-treated soil with undiluted Awamori waste (4.5 wt% carbon) was associated with fewer diseased plants and a higher marketable yield of pumpkin. Additionally, in the greenhouse trial, BSD with Awamori waste containing 0.1 wt% carbon was associated with fewer diseased plants and an improved marketable yield of bitter gourd. In conclusion, Awamori waste represents a highly effective and sustainable material for BSD treatment, and its application should be widely promoted in agricultural fields throughout Okinawa Prefecture.