Soil nematode community structure affected by tillage systems and cover crop managements in organic soybean production

•Changes in soil nematode community indices with regard to tillage system and cover crop in Japan.•Degree of surface soil translocation (DTL) was obtained for radio cesium distribution.•DTL was negatively correlated with the abundance of total nematodes and each trophic levels.•DTL was also negativity correlated with structure index.•NT and minimum soil disturbance have many benefits for establishing soil ecosystems. Information associating the tillage disturbance and its effect over soil nematode communities in different tillage systems has not been thoroughly discussed, especially in Asian countries. We investigated the effect of three tillage systems, i.e., moldboard plow/rotary harrow (MP), rotary cultivation (RC), and no-tillage (NT), and three cover crop treatments (fallow, rye, and hairy vetch) with two manure applications (0 and 1Mgha−1) on nematode communities and degree of surface soil translocation (DTL). This study was conducted in Japanese Kanto region (Andosols) in 2009–2011. We calculated nematode community indices, including channel index, enrichment index, and structure index (SI), based on the composition of nematode assemblages, to infer soil ecosystem condition. DTL was calculated from data on the variation of vertical soil distribution of radioactive cesium-137 deposited following the Fukushima Daiichi nuclear power plant accident in 2011. Tillage system influenced nematode abundance of all feeding groups. Cover crop also affected abundance of bacterial feeders (BAC), fungal feeders and facultative root feeders (FFR), predators (PRD), and obligatory root feeders (ORF). SI was bigger in NT, which was 22% and 47% higher than in MP and RC, respectively. DTL negatively correlated with abundance of BAC, omnivores, ORF, total number of nematode species, and SI, but positively correlated with the abundance ratio of FFR to FFR+BAC. Our results suggested that tillage inversion exerted stronger effects on nematode community and structure of soil ecosystem than cover crop treatment and manure application.