Effects of Substrate and Processing Conditions on Nematode Suppressiveness of Anaerobic Biogas Digestates

Abstract

Biogas digestates produced from anaerobically processed food or dairy manure have demonstrated some potential to suppress different pathogens and pests. In this study, digestates from these two substrates processed mesophilically (20 to 40°C) or thermophilically (>40°C) were compared for their nematode-suppressive potential. In bioassays, the suppressive potential of Heterodera schachtii or Meloidogyne incognita was tested at different amendment rates. Testing was expanded to field microplot experiments with M. incognita and greenhouse tests with Pratylenchus vulnus. In the bioassay with H. schachtii, fewer nematodes penetrated radish roots after amendment with thermophilic than with mesophilic digestates. Root penetration was lowest after treatment with digestates of food waste and thermophilic dairy manure at the highest rate. In a watermelon bioassay with M. incognita, nematode-induced galling and egg mass production were reduced after amendment with food waste digestates compared with manure digestates and after thermophilic compared with mesophilic digestates in the case of egg masses. In a greenhouse experiment with peach rootstock ‘Nemaguard’, the numbers of P. vulnus in roots were diminished after amendment with digestates at the highest rate. In microplot experiments with bell peppers, plants initially were more vigorous after amendment with thermophilic digestates than after mesophilic digestate additions. This effect was transient and was no longer measurable at harvest. In summary, food waste digestates, especially those that were thermophilically produced, had nematode suppressive and plant growth-improving properties. These effects were not long lasting and probably need additional mitigation for practical utility. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .