title: Solubility and cation exchange in phosphate rock and saturated clinoptilolite mixtures.
abstract: Mixtures of zeolite and phosphate rock (PR) have the potential to provide slow-release fertilization of plants in synthetic soils by dissolution and ion-exchange reactions.  This study was conducted to examine solubility and cation-exchange relationships in mixtures of PR and NH4- and K-saturated clinoptilolite (Cp).  Batch-equilibration experiments were designed to investigate the effect of PR source, the proportion of exchangeable K and NH4, and the Cp to PR ratio on solution N, P, K, and Ca concentrations.  The dissolution and cation-exchange reactions that occurred after mixing NH4- and K-saturated Cp with PR increased the solubility of the PR and simultaneously released NH4 and K into solution.  The more reactive North Carolina (NC) PR rendered higher solution concentrations of NH4 and K when mixed with Cp than did Tennessee (TN) PR.  Solution P concentrations for the Cp-NC PR mixture and the Cp-TN PR mixture were similar.  Solution concentrations of N, P, K, and Ca and the ratios of these nutrients in solution varied predictably with the type of PR, the Cp/PR ratio, and the proportions of exchangeable K and NH4 on the Cp.  Our research indicated that slow-release fertilization using Cp/PR media may provide adequate levels of N, P, and K to support plant growth.  Solution Ca concentrations were lower than optimum for plant growth.
authors.affiliation: Dep. of Agronomy, Oklahoma State Univ., Stillwater 74078, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Allen
authors.forename: L R
authors.initials: LR
authors.lastname: Hossner
authors.forename: D W
authors.initials: DW
authors.lastname: Ming
authors.forename: D L
authors.initials: DL
authors.lastname: Henninger
mesh_terms: D002118:Calcium / Q000737:chemistry; D002411:Cation Exchange Resins / Q000737:chemistry*; D005308:Fertilizers / Q000032:analysis; D009584:Nitrogen / Q000737:chemistry; D009751:Nutritional Requirements; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D063245:Plant Development; D011188:Potassium / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012987:Soil / Q000032:analysis; D012995:Solubility; D013997:Time Factors; D017641:Zeolites / Q000737:chemistry*
chemical_list: D002411:Cation Exchange Resins; D005308:Fertilizers; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D012987:Soil; C083175:clinoptilolite; D017641:Zeolites; D010758:Phosphorus; D009584:Nitrogen; D011188:Potassium; D002118:Calcium