Availability of Aluminum Toxicity in Nutrient Solution Using Aluminum Chloride and Aluminum Sulfate.

Not is well established the best source of aluminum (Al³⁺) to produce toxicity in nutrient solution experiments with upland rice, Furlani and Furlani in 1988 cited the Aluminum Sulfate - AlK(SO₄)₂.12H₂O as the best source for use in nutrient solution, however, recent studies using the Chloride Aluminum (AlCl₃.6H₂O). So the objective of this study was to compare the AlK(SO₄)₂.12H₂O e AlCl₃.6H₂O by means of software Visual MINTEQ 3.0 (Gustafsson, 2012) order to define which source is more efficient in generating toxicity to plants of upland rice in nutrient solution. The Al³⁺ concentration studied were 0; 370; 740; 1.110 e 1.480 μmol L^-1, corresponding to Al³⁺ activity solution, estimated by MINTEQ 3.0 of: 0; 85,1; 144,1; 191,2 and 229,7  μmol L^-1 in the AlK(SO₄)₂.12H₂O, respectively and 0; 117,6; 233,0; 336,8 and 429,0 μmol L^-1 in the AlCl₃.6H₂O. Availability of toxic Al³⁺ form in nutrient solution estimated when using AlK(SO₄)₂.12H₂O was 0; 50,74%; 45,54%; 42,32% and 39,81% corresponding to Al³⁺ activity solution 0; 85,1; 144,1; 191,2 and 229,7 μmol L^-1. Using AlCl₃.6H₂O the availability of toxic Al³⁺ form in nutrient solution was 0; 72,42%; 78,41%; 81,92% and 84,20%, corresponding to Al³⁺ activity solution 0; 117,6; 233,0; 336,8 and 429,0 μmol L^-1, respectively. Not is interesting to use AlK(SO₄)₂.12H₂O, because about 50% of Al³⁺ stay in AlSO₄⁺ form, thus, less than half of the Al³⁺ concentration added in solution stay availability in the toxic form for plant. The AlCl₃.6H₂O is more efficient to generating Al³⁺ toxicity in plant, because Al³⁺ is availability in larger quantities in its toxic form in solution. And when used AlCl₃.6H₂O the root rice produce less dry weight comparing to AlK(SO₄)₂.12H₂O, proving AlCl₃.6H₂O more efficient in generating Al³⁺ toxicity in upland rice plants.