Fusarium populations in soil under long-term organic and chemical fertilizer treatments

Fusarium spp. in soil are potential threats to crops, so the purpose of this study was to explore the response of their population levels and species composition to long-term fertilizer applications. Two experiments were established in 1993 (consecutive 13 years) and 1997 (consecutive 9 years), where organic fertilizer (OF) and chemical fertilizer (CF) treatments were conducted in the winter wheatsummer maize rotation system in the North China Plain. Unfertilized soil served as controls. Eight Fusarium species were isolated and identified based on their morphological characteristics and nucleic acid analysis. Four dominant species including F. proliferatum, F. solani, F. equiseti, and F. semitectum accounted for 95% of isolates. No differences in total Fusarium population levels and diversity indices with organic and CF were found. Both fertilizer applications increased population levels of F. equiseti in soil, due to its better competition for nutrients. High nutrients also impacted F. solani population. These two species should be monitored when applying OF and CF. The decrease of F. proliferatum population across the growing seasons was attributed to decomposition of maize debris from preceding crop in soil.