Abstract: A pot experiment was conducted to study the effects of adding different amounts of wheat straw  (0 g·kg^-1, N₀; 2.08 g·kg^-1, N₁) and phosphorus (0 mg·kg^-1, P₀; 100 mg·kg^-1, P₁; 200 mg·kg^-1, P₂; 400 mg·kg^-1, P₃) on microorganism community in a soil of low-phosphorus. Adding straw and phosphorus had significant effects on the soil microbial total biomass (MTB), bacterial biomass (MB), fungal biomass (FB), and fungi to bacteria ratio (F/B), which all decreased in order of N₁P₁>N₁P₀>N₁P₂>N₁P₃> N₀P₁> N₀P₂>N₀P₃. MTB, MB, FB and F/B ratio of the wheat straw addition treatments were all significantly higher than in the non-straw addition treatments under the same level of phosphorus addition. As for the same wheat straw addition, MTB, MB, FB and F/B ratio increased firstly and then decreased with increasing the level of phosphorus addition, and the combinations of P₁ level were optimal.

Key words: straw carbon source, phosphorus, soil microbial community structure, PLFA.