Wheat straw of mature period was decomposed under laboratory conditions:pH5,pH7 and pH8 by microoganisms. Filtrates of rotted wheat straw after 1 day,1 week,2 weeks and 4 weeks of incubation were tested for bioassay,and their some extracts obtained under acidic and basic conditions were analysed by GC-MS. It was found that allelopathic effects of extracts on the germination of wheat and maize seeds are obviously dependent on the period of decomposition, pH value and variety of crops.All acidic extracts show...