title: Assessment risk of phosphorus leaching from calcareous soils using soil test phosphorus.
abstract: Accurate estimation of phosphorus (P) leaching is important because excess P may reduce surface and ground water quality. Little attention has been paid to estimate P leaching from soil tests in calcareous soils. The relation between different soil tests P (STP), P sorption index (PSI) and degree of P saturation (DPS) and leaching of P were examined for assessing the risk of P loss from calcareous soils. Columns leaching repacked with native soils were leached with either distilled water or 10 mM CaCl2solutions, separately. Four leaching events were performed at four days, and 28.7 mm of distilled water or 10 mM CaCl2solutions was applied at each leaching events. Compared with distilled water, CaCl2had a small ability to solubilize P from soils. Concentration of P in leachate in both leaching solutions was exceeding 0.1 mg l-1associated with eutrophication. Cumulative P leached P was ranged from 0.17 to 18.59 mg P kg-1and 0.21-8.16 mg P kg-1, when distilled water and 10 mM CaCl2solutions were applied, respectively and it was higher in sandy clay loam soils compared with clay soils. Among evaluated environmental soil P tests, PCaCl2-3h(P extracted by 10 mM CaCl2for 3 h), PCaCl2-1h(P extracted by 10 mM CaCl2for 1 h) were more accurate than other soil P tests for predicting P concentration in the leachates in both leaching solutions and accounting for 83% and 72% of variation of P concentration, respectively. The water extractable P (WEP) (r = 0.771) and Olsen-P (POls)(r = 0.739) were significantly related to the leached P concentration using distilled water solution in a split line model, with a change point of 27.4 mg P kg-1and 61.5 mg P kg-1, respectively. Various DPS were calculated and related to the leached P concentration. Based on P extracted by Mehlich-3 (PM3) and HCl (PHCl) and PSI, the change point of the relationship between leached P concentration and DPSM3-3(PM3(PM3+PSI)×100) and DPSHCl-2(PHCl(PHCl+PSI)×100) for both leaching solutions was approximately the same, thus a mean value of 49% for DPSM3-3and 73% for DPSHCl-2was obtained. Soils were grouped into four categories of increasing P leaching potential based on WEP, POls, and DPSM3-3. The results indicated that 8.00%-25.50% of the soil grouped in no risk category whereas 8.00%-13.70% of the soils fell into the high risk category.
authors.affiliation: Department of Soil Science, College of Agriculture, Hamadan, Iran. Electronic address: jalali@basu.ac.ir.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Jalali
authors.affiliation: Department of Soil Science, College of Agriculture, Hamadan, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Jalali
mesh_terms: D002122:Calcium Chloride / Q000737:chemistry; D005068:Eutrophication; D010758:Phosphorus / Q000737:chemistry*; D018570:Risk Assessment; D012989:Soil Pollutants / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D012989:Soil Pollutants; D014867:Water; D010758:Phosphorus; D002122:Calcium Chloride
keywords: Phosphorus fertilizers; Phosphorus leaching; Phosphorus losses; Risk assessment; Soil column