Since effective disposable way of anaerobically digested biogas slurry is expected, ADS was applied to soil to evaluate its effects on nematode damage. Damage index of tomato by root-knot nematode was significantly ( ) lower and the growth better in pots applied with ADS (100 and 200？mg -N？kg？1) than that in those with chemical fertilizer and control (no ADS). ADS was applied into radish cultivated fields infested with the root-lesion nematode: a single (100？kg -N？ha？1) in 2007 and 2008 and multiple applications (25, 50, 25？kg -N？ha？1 soil) in 2009. Damage to radish was 30% and 50% lower in ADS-treated fields than that in the control in 2007 and 2009, respectively, although not in 2008. These results suggest that application of ADS to fields might be feasible for mitigating nematode damage, but the rate and timing should be considered further for the best application way. 1. Introduction How to dispose byproduct of biogas plants into our environment is now becoming an important issue. Direct application to agricultural land is one of the most probable options. The byproduct, anaerobically digested slurry (ADS) from animal wastes, has been evaluated as a potentially important alternative source to synthetic inputs [1] in sustainable crop production. In addition, protection of plant-parasitic nematodes and phytopathogenic fungi [1–7] by ADS has been reported, and its ingredients such as ammonium and acetic acid are proposed as possible mechanisms [6]. In addition, it is discussed that plant-parasitic nematodes are controlled by certain kinds of organic amendment through the stimulation of naturally occurring antagonists [8, 9] for nematodes pests and/or change of the soil nematode community structure [10]. We have previously reported on the ability of different types of ADS to suppress the root-lesion nematode Pratylenchus penetrans and root-knot nematode Meloidogyne incognita in in vitro experiment without the host plants and the possible mechanisms involved [6]. The objective of this study was to evaluate the effectiveness of ADS on the plant-parasitic nematodes in larger scales of experiment, such as pot and field with the host plants. The Miura Peninsula in Kanagawa Prefecture is a major radish production area of Japan, and damage caused by P. penetrans is the major threat to the farmers since it reduces radish quality [11]. Therefore, potential nematicidal action of ADS was tested for the damage by nematode in conventional radish cultivated fields in the area. In addition, effect of ADS on damage to tomato by root-knot nematode disease M. incognita
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