Species composition and spore density of indigenous vesicular-arbuscular mycorrhizal fungi under different conditions of P-fertility as revealed by soybean trap culture

The influence of soil treatment over a period of 8 y on the species composi tion and spore density of indigenous VA mycorrhizal fungi was investigated in relation to phosphorus (P) accumulation. Soils were collected from an ex perimental field which was subjected to four different treatments: applicat ion of farmyard manure (FYM), application of chemical fertilizer (CF), no f ertilizer application (NF) (mainly melon-cabbage had been cultivated), and grassland (alfalfa meadow, chemical fertilizer had been applied) (GL). P (T ruog-P) shows large accumulation in the FYM- and GL-soils, 7,782 and 2,631 mg P2O5 kg(-1) soil, respectively, compared to the accumulation in the CF- and NF-soils, 790 and 101 mg P2O5 kg(-1) soil, respectively. Indigenous fun gi were first multiplied by soybean trap culture prior to the observation o f the fungal communities. Glomus sp. B1 was common to all of the four soils , and the number of spores was significantly higher in the NF-soil. Glomus sp. Y1 was commonly found in the FYM-, CF-, and NF-soils but not in the GL- soil. Glomus sp. R1 was dominant in the FYM-soil and not found in the other soils. Acaulospora sp. N1 was specifically dominant in the GL-soil. These results suggest that very high-P conditions may influence the species compo sition of the fungi.