Ramin Salmasi; Mohsen Farahbakhsh; Hossien Asadi
Abstract
Phosphorus (P) loss in runoff can promotes weed and algae growth in water systems as a result of high concentrations of surface water P. As a result, relationship between available soil P and P concentrations is necessary for management of P concentrations in surface waters and for critical soil P determination. ...
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Phosphorus (P) loss in runoff can promotes weed and algae growth in water systems as a result of high concentrations of surface water P. As a result, relationship between available soil P and P concentrations is necessary for management of P concentrations in surface waters and for critical soil P determination. For this purpose, from 30 points of Talkherood Watershed surface soil samples with widely available P contents were selected. After determining some of general properties, four soil P tests including Olsen, Mehlich-3, Iron oxide and Soltanpour were measured. Then, soil samples were poured with imperative compaction and rainfall was applied onto 30×60 cm soil boxes on a 5% slope for 30 minutes by applying 75 mm h-1 rainfall. Their runoff was sampled in different times and their dissolved P concentration was measured. Significant correlation was obtained between dissolved runoff P and the four methods of available P for the soils. Critical concentrations of phosphorus for Olsen, Mehlich-3, Iron oxide, and Soltanpour methods were 86, 140, 52 and 49 mg l-1, respectively. Also, the four methods showed critical dissolved runoff P concentrations in narrow range of 0.38 to 0.4 mg l-1.
Ramin Salmasi; Mohsen Farahbakhsh; Hossein Asadi
Abstract
There is critical need for a practical indicator to assess the potential of phosphorus (P) movement from a given site to surface waters, either via surface runoff or subsurface drainage. The Degree of P Saturation (DPS), which relates a measure of P already adsorbed by a soil to its P adsorption capacity, ...
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There is critical need for a practical indicator to assess the potential of phosphorus (P) movement from a given site to surface waters, either via surface runoff or subsurface drainage. The Degree of P Saturation (DPS), which relates a measure of P already adsorbed by a soil to its P adsorption capacity, could be a good indicator of that soils P release capacity. For our country soils, there is not any report for DPS calculating. This study aimed to develop techniques of calculating the DPS for calcareous soils of western Azerbayjan, Uremieh Lake sub-watershed, obtaining DPS levels for calcareous soils, and evaluating DPS by use of soluble P as indicator of P runoff potential. For this purpose, 30 surface soil samples with widely P contents were selected and after determining some of general physico-chemical properties, useing of four measures of soil available P and four indices of P sorption capacity, sixteen different forms of DPS were obtained. Significant correlation was obtained between soluble P and different forms of DPS in this study. Threshold P concentration between four extractants, were obtained for Olsen, Mehlich-3, and Soltanpour ones, except in calculations with Mg as P adsorbed contributor in range of 0.4-33 percent, with 8.14 mean, and for FeO extractant, only in calculations with Ca + Mg as adsorbing one was obtained that was equal to 1.3 percent. Degree of P saturation in soils with higher than threshold P concentration values are sustainable to P runoff via surface runoff or leaching, and as a result eutrophication intensification, and for control this phenomenon should apply management practices with regard to different situations of watershed.