Phosphate Sorption by Soils: II. Sorption Measurement Technique

Abstract A computer‐controlled apparatus has been developed for measurement of P sorption by soils. A solution containing P is constantly pumped from a vessel through a soil column and back to the vessel again. Phosphorus concentration in the vessel can be assessed and regulated; constant, increasing and decreasing concentration are optional. The method of pumping solution through a column is convenient for relatively slow reactions and for reactions in which a high soil/solution ratio is required. When a high pumping rate is used, the results are comparable with classical batch experiments. The proposed method, however, has many advantages, e.g., avoiding mechanical disturbance of the soil particles and separating solids from solution. Eight soil samples can be examined at one time. This makes the apparatus suitable for routine as well as research experiments. The analytical part of the apparatus can easily be replaced; other ions of interest (K + , Mg 2+ , trace elements) can then be studied in the same way.