Effects of endomycorrhizas on the competitive ability of white clover

White clover ( Trifolium repens L.) and ryegrass ( Lolium perenne L.) were grown separately and together, at five soil P levels, and with or without vesicular‐arbuscular mycorrhizas (VAM). At 0 kg P/ha VAM produced a 5‐fold increase in total clover dry weight when grown alone and a 40‐fold increase when grown with ryegrass. In the absence of tyegrasss total clover dry weights were increased by VAM at 0 and 4 kg P/ha while in the presence of ryegrass, clover P concentrations were depressed and VAM stimulated clover growth at 12 kg P/ha. By the third harvest VAM stimulated clover grown alone at 12 kg P/ha although it did not significantly stimulate total yield. The results show that VAM clover is better equipped than non‐mycorrhizal clover to compete with ryegrass for soil P and that inter‐ and intra‐specific competition for soil P resulted in VAM stimulating clover more and at higher soil P levels. Ryegrass displayed a poor response to both P and VAM, which was attributed to N deficiency.