Seasonal variation in infectivity of vesicular-arbuscular mycorrhizal fungi in relation to plant response to applied phosphorus

The effect of applied phosphorus on the growth of subterranean clover was studied in a virgin forest soil sample collected in summer and again in spring. The soil sample was used soon after it was collected.The shape of the response curve for plant growth differed greatly in the two experiments. This may berelated to the presence of vesicular-arbuscular mycorrhizal infection in plants grown in the soil samplecollected in summer and its absence in the soil sample collected in spring.