GROWTH AND NUTRIENT-UPTAKE OF SORGHUM CULTIVATED WITH VESICULAR-ARBUSCULAR MYCORRHIZA ISOLATES AT VARYING PH

This study was conducted to determine the effects of different pH regi mes on root colonization with four vesicular-arbuscular mycorrhiza (VA M) isolates, and VAM effects on host plant growth and nutrient uptake. Sorghum [Sorghum bicolor (L.) Moench] was grown at pH 4.0, 5.0, 6.0 a nd 7.0 (+/- 0. 1) in hydroponic sand culture with the VAM isolates Glo mus etunicatum UT316 (isolate E), G. intraradices UT143 (isolate I), G . intraradices UT126 (isolate B), and an unknown Glomus isolate with n o INVAM number (isolate A). Colonization of roots with the different V AM isolates varied differentially with pH. As pH increased, root colon ization increased with isolates B and E, remained unchanged with isola te I, and was low at pH 4.0 and high at pH 5.0, 6.0, and 7.0 with isol ate A. Isolates E and I were more effective than isolates A and B in p romoting plant growth irrespective of pH. Root colonization with VAM a ppeared to be independent of dry matter yields or dry matter yield res ponsiveness (dry matter produced by VAM compared to nonmycorrhizal pla nts). Dry matter yield responsiveness values were higher in plants who se roots were colonized with isolates E and I than with isolates A and B. Shoot P concentrations were lower in plants colonized with isolate s E and I than with isolates A and B or nonmycorrhizal plants. This wa s probably due to the dilution effect of the higher dry matter yields. Neither the VAM isolate nor pH had an effect on shoot Ca, Mg, Zn, Cu, and Mn concentrations, while the VAM isolate affected not only P but also S, K, and Fe concentrations. The pH x VAM interaction was signifi cant for shoot K, Mg, and Cu concentrations