Abstract
The total amount of phosphorus in a volcanic ash soil type adsorbent adsorbing phosphate from secondary effluent (used volcanic ash soil type phosphate adsorbent) is 13.8gP · kg-1, mainly consisting of aluminum combination type phosphorus, and the amount of citrate-soluble phosphorus is 57%. A though this used volcanic ash soil type phosphate adsorbent is not suitable as a phosphate fertilizer according to the Fertilizer Regulation Law, it is found suitable as a soil amendment matter with a phosphate supply function because of its high amount of citrate-soluble phosphorus. The soil physics of the subsoil of andosol seldom changes with the application of the used volcanic ash soil type phosphate adsorbent. However, this absorbent has a large effect of promoting the growth of Brassica campestris cv. Komatsu, and is more effective than superphosphate. Moreover, its phosphorus adsorption rate low at only 0.8%, which proves that it is very promising for soil reduction and recycling.
