Induced toxicities of aluminum and manganese in sweet sorghum: III relations between P, Mg and AL

Four varieties of sweet sorghum (CMSxS603), Br500, Sart and Br602) were qrown in a modified Hoagland's solution in order to supply varyinq levels of Al, P and Mg. After harvesting dry matter was measured both in roots and tops, and analyses for P, K, Ca, Mg and Al were made. The following was observed: a) tolerance of the varieties was better indicated by root dry matter according to a decreasing order - Sart, CMSxS 603, Br 500, Br 602; b) when the Mg concentration in the substrate was raised, tolerance to Al toxicity was increased provided P was supplied at a relatively high level; c) maximum and minimum dry matter yield of the tops were associated with P, K, Ca, Mg and Al contents which were different for the four varieties; d) depending upon the variety and of the supply of the other nutrients (P and Mg) a stimulation on growth was caused by low Al levels in the nutrient solution.