Comparación de métodos radiométricos y colorimétricos en estudios sobre retención y transformación de fosfato en el suelo

Abstract

The colorimetric and tracer techniques for phosphate retention and transformation in soils were compared in 10 soil samples from Costa Rica. Phosphate retention was determined by shaking 0.5g soil with 25 ml of a KH₂PO₄ solution tagged with ³²P and containing 100 μg P/ml. The transformation of phosphates was investigated by Chang and Jackson's fractionation technique and the P in the different extractions was determined colorimetrically and by its radioactivity. The retention results obtained with the two methods were almost identical and the correlation coefficient between both was r 0.998. For the data on P transformation, high correlations were found for aluminium and iron phosphate and the NH₄Cl soluble fraction. For the calcium phosphate fraction, which is of very little importance in these soils, no significant correlation could be found. Based on the data, the colorimetric and the tracer method are equally adequate. However, the use of the tracer technique permits more rapid and accurate determinations.