Phosphorus Adsorption by Heated Soils

To enhance the phosphorus adsorption by soils, we examined several distinct characteristics of different soils by subjected to heating treatment. Then, the relationship between the amount of phosphorus adsorbed and the various nature characteristics of soils, and the mechanism of the increase in phosphorus adsorption were examined. The results are outlined below. With three soil types (volcanic ash soil, brown forest soil, red soil), the increase in phosphorus adsorption caused by heating, was maximum at 500 degree C. Phosphorus adsorption differed depending on soil types, and the amount of phosphorus adsorbed was in the order of volcanic ash soil> brown forest soil > red soil at 500 degree C. Volcanic ash soil, brown forest soil, red soil needs 300 degree C, 200 degree C and 300 degree C, respectively, of heat temperature in order to achieve the maximum specific surface area. The amount of silicon from oxalate extraction dissolution was maximum at 300 degree C in the volcanic ash soil, and was maximum at 500 degree C in both the brown forest soil and the red soil. Furthermore, each of the three types soil achieved the maximum amounts of both active aluminum and free aluminum at 500 degree C, and the maximum amounts of both active iron and free iron at 300 degree C. One of the factors affecting phosphorus adsorption by heated soils is soil type. We confirmed that the amount of phosphorus adsorbed onto these three soil types commensurate with the amount of active aluminum, free aluminum and silicon from oxalate extraction dissolution.