Abstract: Physical and chemical properties, culturable bacterial population and phospholipid fatty acid (PLFA) profile of different casing soils at different mushroom ( Agaricus bisporus ) cropping stages were investigated. The air-filled porosity (AFP), water retention and water released under -2.16 kPa — -17.28 kPa of the casing soils increase with the increasing in the ratio of peat to soil. The results of phospholipid fatty acid (PLFA) analysis indicated that mycelium biomass of Agaricus bisporus in 100%, 50% and 30% peat casing were significantly higher than that of traditional casing --soil with rice husk ( significant at P<0.05), and the increase in the ratio of peat to soil was accompanied by an increase in mycelium biomass. Comparatively higher mycelium biomass of Agaricus bisporus were found in all casing soils at the primordia stage of second flush. The increase of mycelium biomass of Agaricus bisporus in casing was accompanied by an increase in the bacterial population. The result may indicate the syntrophism between bacteria and mycelia during growth of mushroom. There is a strong positive correlation between the number of mushroom primordia and mycelium biomass in casing, and the yield of mushroom positively correlated with number of mushroom primordia and moisture content of casing soil. The important aspects of casing soil improvement are to increase mycelium biomass and water retention in casing.

Key words: Agaricus bisporus, casing soil, physical and chemical properties, phospholipid fatty acid, mycelium biomass, bacterial population, yield