Determinação do valor t-s na terra roxa legítima e a aplicação da fórmula Vageler

Paiva Neto, J. E. de

doi:10.1590/S0006-87051942000900003

Resumo

The present work is a study of Vageler's formula y =x.S/ x+y.S for the determination of the final value of the reaction of the cation change in the sorptive complex of the soil. The author took the changeable H+ of the soil as a cation to be examined. Samples studied by the author belong to a chain (a series of soil profiles with 5 horizons each) taken from the original red soil ("terra roxa") of the Ribeirão-Preto Experiment Station. In these samples, as a rule, H+ changed could be considered = T - S, because the Al changed, as far as it existed, was traced in very low percentage, as can be seen in table I. For the determination of T - S, the author used a solution of (CH3COO)2Ca N/l (normal calcium acetate). As a mean of extraction, the percolation of the solution of calcium aceta te through a layer of soil was used instead of the shaking method. From what has been pointed out, it may be concluded that the application of the Vageler formula for the determination of the final value of this reaction is correct and of great advantage. A great amount of material and time is also saved. Besides, the percolation in this kind of work offers a great advantage over the shaking method, consisting of the extraction of changeable ions from the sorptive complex of soil. It has also been observed that the index T - S in this kind of soil is affected by the topography and shows that the more the soil is percolated by water the larger will be the above mentioned index. It has also become evident that organic matter does not contribute in a great extent to the variation of the index T - S.

SUMMARY

The present work is a study of Vageler's formula y =x.S/ x+y.S for the determination of the final value of the reaction of the cation change in the sorptive complex of the soil. The author took the changeable H+ of the soil as a cation to be examined. Samples studied by the author belong to a chain (a series of soil profiles with 5 horizons each) taken from the original red soil ("terra roxa") of the Ribeirão-Preto Experiment Station. In these samples, as a rule, H+ changed could be considered = T S, because the Al changed, as far as it existed, was traced in very low percentage, as can be seen in table I. For the determination of T S, the author used a solution of (CH₃COO)₂Ca N/l (normal calcium acetate).

As a mean of extraction, the percolation of the solution of calcium aceta te through a layer of soil was used instead of the shaking method. From what has been pointed out, it may be concluded that the application of the Vageler formula for the determination of the final value of this reaction is correct and of great advantage. A great amount of material and time is also saved.

Besides, the percolation in this kind of work offers a great advantage over the shaking method, consisting of the extraction of changeable ions from the sorptive complex of soil. It has also been observed that the index T S in this kind of soil is affected by the topography and shows that the more the soil is percolated by water the larger will be the above mentioned index. It has also become evident that organic matter does not contribute in a great extent to the variation of the index T S.

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LITERATURA CITADA

1. Swanson, C. O., P. L. Gainey e W. L. Latshaw. The calcium content of soil in relation to absolute reaction. Soil Science XVII : 181-191. 1924.
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