GROWTH EFFECTS OF THE VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGUS-GLOMUS CONSTRICTUM ON MAIZE PLANTS IN POT TRIALS

Maize plants were inoculated with Glomus constrictum in soil of low ph osphorus content amended with five rates of P in the form of Ca-3(PO4) (2). Maize dry matter yield was increased by addition of P up to 30 an d/or 60 mg P/kg soil, above that it began to decrease to reach at 100 mg P/kg a value similar to that of the control. At all P levels used, the shoot and root (total plant) dry mass of inoculated plants was sig nificantly increased compared with the non-inoculated controls and thi s increment ranged in some cases between 50 and 70 %. Development of v esicular-arbuscular mycorrhizal fungus (VAM) monitored in terms of P c ontents in dry matter of maize revealed that the P content of plants n ot inoculated with G. constrictum was not influenced by P addition to soil. On the other hand, P content of maize plants inoculated with VAM was dramatically increased by increasing P levels of soil and was max imum at 30 mg P; above that it began to decline. Mycorrhizal root infe ction (expressed as percentage of root length infected) increased by i ncreasing the P concentrations above the soil basal level up to 80 mg P where the infected root length was 72 % of the total root length aft er 28 d of planting. The increase in VAM spore formation in soil was s imilar to that of root infection except that the highest spore number was sieved from soil at 60 mg P/kg soil.