Abstract: A pot culture experiment was carried out to study effects of application rate of used Agaricus bisporus culturing medium,called mushroom castoff(MC),on plant growth of Vigna radiate and arbuscular mycorrhizal fungal infection in its root system.With arbuscular mycorrhizal fungi(AMF) inoculation,the addition of MC at a rate of 5% to 50% increased AMF infection rate,plant biomass and economic yield to a varying extent.The infection rate peaked around D35 after sowing.The addition of MC at a rate of 20% benefited the plant in growth the most,compared to the controls,the shoot length increased by 58%,plant biomass increased by 128%,bean pod dry weight increased by 598% and bean dry weight increased by 577% on D60 when the plant was harvested.A significant linear regression relationship was observed between the economic yield(bean dry weight) and the AMF infection rate on D35(P<0.05),which suggests that application of MC at a rate of ca.20% benefits the most vegetative and productive growth of the plant and AMF infection in its root system.Besides,no significant difference was found between sterilized and non-sterilized substrates in AMF infection rate in Vigna radiate root system,which indicates that MC accelerates AM infection in plant roots and,therefore,propagation of AMF.