Renewable, controlled and environmentally safe phosphorus release in soils from mixtures of NH4 +-phillipsite tuff and phosphate rocks

 The renewable and controlled-release fertilization system investigated here uses NH₄ ⁺-exchanged phillipsite tuff, from Jordan, to help in the dissolution of phosphate rock. Accordingly, controlled and renewable soluble nitrogen, phosphate and Ca are released as nutrients for plants. NH₄ ⁺ phillipsite can sequester Ca ions released by the dissolution of phosphate rock, therefore, leading to further phosphate rock dissolution. In this study the results show that the amount of phosphate released is more than that released by phosphate rock alone. This method offers an alternative to the use of highly soluble fertilizers and may avoid environmental problems associated with their extensive use in agriculture. Received: 22 May 1997 · Accepted: 12 August 1997