Influence of Long-Term Fixed Fertilization on Diversity of Arbuscular Mycorrhizal Fungi

Diversity of arbuscular mycorrhizal fungi (AMF) was investigated in a field that had received long-term fixed fertilization (LFF) for 26 years. There were a total of 12 treatments in triplicates with different amounts of manure, urea, calcium phosphate, and potassium chloride. Rhizosphere soil samples of maize and wheat grown in the experimental field in Shandong Province, China, were collected in September 2003 and May 2004, respectively. Arbuscular mycorrhizal fungal spores were isolated and identified using morphological characters. Mycorrhizal colonization percentage, spore density (SD), species richness (SR), relative abundance (RA), and Shannon-Weiner index (SWI) were determined. Nineteen recognized species of AMF belonging to 5 genera were identified. Long-term fixed fertilization significantly influenced colonization percentage, SR, SD, and species diversity of AMF. The adaptability of AMF to soil fertility was different among species. Species richness and SD of AMF in maize and wheat rhizosphere soils were the highest in the nonfertilization treatment (control) and lowest in the high manure + high nitrogen treatment (M2N2). The SWI decreased as the fertilization level increased except in the low manure treatment (M-1) on maize. Compared with the other treatments, Treatment M2N2 significantly reduced SD of Glomus, and the high manure + low nitrogen treatment (M2N1) significantly retarded sporulation of Scutellospora. Manure treatments stimulated sporulation of Glomus mosseae. Spore density of G. mosseae was higher in the high nitrogen + phosphorus + potassium treatment (N2PK) than in the high nitrogen + phosphorus treatment (N2P) and the high nitrogen + potassium treatment (N2K). The SD of S. pellucida was higher in Treatment N2K than Treatments N2PK and N2P. In conclusion, long-term fixed fertilization, especially with high levels of manure and N, decreased SR, SD, and colonization and changed the species composition of AMF.