Saprotrophic fungal communities in arable soils are strongly associated with soil fertility and stoichiometry

The importance of soil saprotrophic fungi in agroecosystems is receiving increasing attention. However, the linkages between saprotrophic fungal communities and soil fertility and stoichiometry in agroecosystems are poorly understood. Here, four long-term field fertilization experiments with three treatments (i.e., no fertilizer (control), chemical nitrogen (N), phosphorus (P), and potassium (K) fertilizer (NPK), chemical combined with organic fertilizer (NPKM)) were performed to evaluate the associations of saprotrophic fungal communities with the soil fertility index (SFI) and stoichiometric carbon (C):N:P ratios. Long-term NPKM application increased the SFI by 57.66%-129.50% at the four sites, and the SFI was strongly correlated with the saprotrophic fungal community composition, which indicated that exogenous organic matter improved soil fertility to a large extent and stimulated the growth of saprotrophic fungi in arable soils. The soil C:P and N:P ratios were notably decreased in the fertilization treatment, indicated that P was sufficient. Further, the composition of saprotrophic fungi was significantly related to the C:N and N:P ratios, suggested that N status is an important factor for soil saprotrophic fungal communities. Our study provides empirical evidence that the saprotrophic fungal communities in arable soils are strongly associated with soil fertility and stoichiometry and offers guidance for improving soil fertility by regulating the saprophytic fungal community.