Formas y disponibilidad de fosfatos de los suelos de la cuenca baja del Río Choluteca, Honduras

Abstract

The phosphorous status of the ten soil series in the lower basin of the Choluteca river, in Honduras, was studied. This element was chosen as it is one of the most limiting factors of the agricultural productivity of the area. The following conclusioons can be reached. 1. On the average, total P is higher for the alluvial soils than in soils derived from volcanic materials. Inorganic P contributes more than organic P. 2. In the recent alluvial soils, the concentration of calcium phosphates is high, forming the main inorganic P fraction. Occluded phosphates are dominant in the soils formed in situ on volcanic materials. 3. Chemical weathering and degree of development can be adequately measured by the distribution of phosphate fractions in all soils of thearea. 4. A direct correlation was observed between the calcium phosphate content and the pH of the soils studied. There was also a significant inverse correlation between pH and the aluminum and ferric phosphates. 5. Phosphate retention is moderate and inverse correlating with the soil pH. 6. Dry matter production and plant absorption of P were correlated with the P concentration in the NH4Cl soluble fraction, with aluminum phosphates and also with the calcium phosphates. 7. The above mentioned correlations were best evaluated by the Olsen extraction technique. This method gave highly significant correlations, allowing a much better estimation than the Mehlich or Bray l techniques.