Growth response of white clover to vesicular-arbuscular mycorrhizal infection with different levels of applied phosphorus

The growth response of 'Grasslands Huia' white clover (Trifolium repens L.) to infection by Glomus fasciculatum (Thaxter sensu Gerdemann) Gerdemann & Trappe was investigated in 2 phosphorus (P)-deficient soils supplied with various levels of soluble phosphate. Significant shoot yield increases in mycorrhizal plants were obtained in successive harvests at all P levels. However, the magnitude of the mycorrhizal response decreased with increase in P levels or with successive harvests. The percentage of mycorrhizal root infection also decreased with increase in P levels for both soils. Some abnormalities in the mycorrhizal infection units were noted at the highest P levels in both soils, whereas infections at the lower P levels appeared normal and typical of G. fasciculatum in white clover.