[Use of zeolites to solubilize Venezuelan phosphate rock in acid soils]
1995
Mohsin, M. | Larez, R.
Two experiments were performed, one of incubation and the other in green house, to study the role of zeolites, cation exchange agents, on the disolution of two phosphate rocks (PRs) from Navay and Riecito in an acid soil (Jusepin Ultisol, the state of Monagas). In the first trial, the application of PRs combined separately with a zeolite (Z), Union Carbide, in different proportions of 1:0, 0,5:1, 1:1, 2:1, 3:1, 4:1 and 5:1 between Z and a PR, in this acid soil increased significantly their solubility (Olsen P). The higher values for soluble P were obtained for the zeolite and rock combinations of 2:1 and 5:1. It was observed that in the green house experiment with triple superphosphate (TSP) and the PRs mixed separately with a Val for zeolite, added in the ratio of 0:1, 1:1 and 2:1 between the Z and PR, the TSP produced the highest yield of dry plant matter of Pangola grass in the first cutting but its effect reduced markedly and the treatments of PRs with the zeolite surpassed those of the TSP in the successive three cuttings. The accumulative effects of each treatment of a PR, with or without a zeolite, on total dry matter yield of the pasture in four cuttings was similar or higher than those found for the respective TSP doses. Two PRs were statiscally equal but that of Navay showed a better response. The TSP treatments produced better results for the content of P extracted from de soil, P in plant tissues and P removed by the plants. The addition of ion exchange medium caused a decrease in the uptake of calcium by the plants. This showed that the mixed zeolite sequestrated the disolved Ca++ from the soil solution which demonstrated that this material would serve as a solubilizing additive for PRs in acid soils.
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