The inoculum potential of arbuscular mycorrhizal fungi in soil amended with swine slurry

Purpose: This study was carried out to evaluate the effects of the tillage system and consecutive application of swine slurry for seven years on arbuscular mycorrhizal fungal abundance and infective propagules in Brazilian soil with crop rotation. Method: The spore density, the external mycelium, and the most probable number of infective propagules of mycorrhizal fungal abundance were assessed in soil samples from an Oxisol in a long-term field experiment in response to soil management (no-tillage and conventional tillage) and following successive application of swine slurry (0, 30, 60, 90 and 120 m3·ha-1·year-1). Results: A greater amount of external mycelium was observed in soil under no-tillage, while mycorrhizal fungal abundance spore density was greater in soil under conventional tillage. In soil under no-tillage, mycorrhizal fungal abundance infective propagules were more abundant; however, in soil with both management systems, this variable was reduced with different levels of swine slurry application. In no-tillage, the main source of mycorrhizal fungal abundance propagules is the external mycelium, while in conventional tillage, the main inoculum component is the spores. Conclusion: In this study, we verified that the application of swine slurry, with high phosphorus contents, reduces arbuscular mycorrhizal fungi propagules. However, these effects are mitigated in no-tillage systems compared to conventional tillage. Highlights Swine slurry application in soil reduces infective propagules of mycorrhizal arbuscular fungal. Soil disaggregation caused by conventional tillage increases sporulation and reduces infective propagules of mycorrhizal arbuscular fungal. Reduction of infective propagules of mycorrhizal arbuscular fungal under swine slurry application is mitigated in no-tillage systems.