Soil amendment with digestate from bio-energy fermenters for mitigating damage to Beta vulgaris subspp. by Heterodera schachtii

Soils benefit from organic matter inputs to increase their carbon pool and replenish plant nutrient contents. In Germany, the surge of biogas production from whole-plant silage of maize results in large amounts of digestate. Research projects have addressed the use of this material in nutrient cycling and the potential for pathogen transfer through biogas fermenters. Nematode suppression has been associated with organic soil amendments. Management of Heterodera schachtii relies heavily on agronomic practices and cultivar selection for suppressing this soil pest. Here, evaluations of the potential for soil and plant health benefits of anaerobically and mesophilically generated digestate from maize silage are reported. In one microplot experiment with Beta vulgaris altissima, Heterodera schachtii-infested soil was amended with 0.5-, 1-, and 2-fold of commercial rates of the digestate or mineral fertilizer. Amendment with the digestate reduced primary nematode infection and improved plant growth, three weeks and five weeks after planting, respectively. In a second experiment with B. vulgaris vulgaris, rates were 0.25-, 0.5-, 1-, and 2-fold the commercially used rate, and similar early-season results were obtained. One month after digestate application, bacterial but not fungal communities associated with nematodes in soil were only slightly affected by the treatment. Digestate had nematode suppressing properties that warrant further exploration for its efficient use.