Categorías de fósforo en los principales grandes grupos de suelos en la Amazonía de Brasil

Abstract

In 46 soil samples taken from different depths from 12 profiles representative of the seven main Great Soil Groups of the Brazilian Amazon region, their organic, total, Ca-Al-Fe and water soluble phosphates were determined. It was observed that these heavily weathered soils are generally low in total P (av. 359 ppm). The organic phosphate fraction is also small and in 70% of the soils, it represents 20 to 50% of the total P present. The largest inorganic P fraction corresponds to the occluded and reductant soluble phosphates, only indirectly determined here. In most of the soils (70% of them), Ca and water soluble phosphate contribute with less than 10% of the total inorganic P present. The C/P and N/P organic ratios found were rather variable, reflecting the heterogeneity of the soil groups studied. Their values varied between 1325 and 6.1 and between 6.7 and 1, respectively. The average for the two ratios are 217 and 15.7. Based on the results presented here and in the literature, it is believed that the use of phosphatic fertilizers could result in increased production.