Residual effects of hairy vetch (Vicia villosa Roth) on the soybean-root associated fungal community in a low fertility soil

Despite the established benefits of hairy vetch ( Vicia villosa Roth. L), little is known about its effects on fungal community in low-fertility soils, which is critical in organic cropping systems. We established an organic hairy vetch-soybean cropping sequence in northeast Germany to investigate the temporal dynamics of soil mineral nitrogen and soybean root-associated fungal communities, as well as their influence on soybean growth and yield in rainfed conditions. One-season cultivation of hairy vetch significantly altered soil mineral nitrogen content while many other soil chemical properties remained unchanged. Nodulation and grain yield in soybeans were suppressed in the hairy vetch treatment, despite an increase in shoot nitrogen uptake. Correlation analysis revealed positive relationships between soil mineral nitrogen and most soil fungal families studied. Soil fungal community varied with cover crop, soil sample type and sampling time. While fungal diversity was generally higher in bulk soils and comparable across treatments, the hairy vetch cover crop had greater rhizosphere diversity. Aspergillaceae and Nectriaceae were the most predominant families, exhibiting high abundance in soybean rhizosphere but lesser amounts in the hairy vetch. Penicillium janczewskii was present in all plots, with the highest prevalence in the soybean rhizosphere, but its dominance decreased as soybean growth advanced. This study reports the presence of Fusarium solani associated with soybean in the study area, noting its predominance in the rhizosphere soil of the fallow treatment. Our results imply that the dynamics of soil fungi in response to different cover crops may influence soybean growth in organic cropping system.