Ramin Salmasi; Mohsen Farahbakhsh; Hossein Asadi
Abstract
High soil phosphorus (P) can increase the amount of runoff P and cause pollution of P in water bodies. In this paper, to select the best method between laboratory extracting and rainfall simulator method for determining environmental threshold level of P concentration was compared. For this purpose, ...
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High soil phosphorus (P) can increase the amount of runoff P and cause pollution of P in water bodies. In this paper, to select the best method between laboratory extracting and rainfall simulator method for determining environmental threshold level of P concentration was compared. For this purpose, surface soil was sampledfrom 30 points of Talkherood Watershed inEastern Azerbayjan with widely available P contents. After determining some of general properties, four soil P tests comprising Olsen, Mehlich-3, Iron oxide, and Soltanpour were used. Water soluble P in lab was measured and runoff soluble P of soils was determined with using rainfall simulator by applying 75 mm h-1 rainfallfor 30 minutes. Relationship between P concentrations determined by four methods with a) water soluble soil P, as P loss index, and b) runoff soluble P, showed that environmental soil P concentration can be estimated by both lab extracts and rainfall simulation methods for lime soils of this region. As the lab extracts method are easier and less time-consuming, this method is recommended for threshold concentration estimation. Since in iron oxide method, slope difference between the two split-lines was greater than other methods and high correlation coefficients were obtained for all of the methods, as a result iron oxide method is better than others for threshold concentration estimation of available P concentration. Since changing point for dissolved reactive P was seen in 0.36 mg l-1 concentration, as a result this concentration is lower than environmental P concentration for eutrophication phenomenon.
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.
