A Microscopic Determination of Apatite and a Study of Phosphorus in Some Nebraska Soil Profiles

A microscopic method is described for the determination of apatite mineral frequencies. The technique was developed from further study and application of a method used to detect alkaline earth carbonates in soils. Essentially, the method consists of distributing soil heavy minerals over 2 to 3 drops of 10.7 N H 2 SO 4 on a glass slide. Needle‐like calcium sulfate crystals develop on the surface of the apatite grains making them easily recognized. The low birefringence of apatite is used as a further identifying characteristic. A study of three Nebraska soils was made using this technique. Data on the occurrence and vertical distribution of apatite in these soils is presented. A general tendency for the apatite content to increase with depth was noted. This increase is shown to parallel the profile distribution of acid‐soluble phosphorus in these soils. There was a close correlation between the total phosphorus content of the sand and coarse silt and the percent of apatite as determined by this method.