Phosphorus status of some Ethiopian soils

Abstract

The content and distribution of total, organic and different inorganic P fractions were studied in some Ethiopian soil profiles selected to represent the main soil types. Total P was relatively low in most soils except for the alluvial soils of Melka Werer with an average maximum value of 1266 ppm. The organic P found in lower horizons of some soils suggested either a translocation of organic materials down the profiles (Jima) or a stratification for deposits of ash (Awassa) and alluvium (Melka Werer). The relative abundance of the inorganic P forms interacting with the soil solution was generally Fe-P > Al-P > Ca-P > reductant soluble P. In particular, for Holeta and Bako, Ca-P was higher than Al-P going down the profile whereas Ca-P was the most abundant form in Melka Werer soils. The non-extractable or residual P form was relatively large except in less well drained soils. The amount and distribution of the inorganic forms were indicative of weathering in the soils with good drainage. The available P status was generally limited and reflected the low content of contributing active P forms.