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.
Mahbobeh Kiani Harchegani; Seyed Hamidreza Sadeghi; Hossein Asadi
Abstract
Water erosion comprises major processes of the detachment, entrainment, transport and deposition. Sediment washed out from the watershed is composed of different particle sizes. The particle size distribution of sediment is a significant factor influencing detachment and transport processes. However, ...
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Water erosion comprises major processes of the detachment, entrainment, transport and deposition. Sediment washed out from the watershed is composed of different particle sizes. The particle size distribution of sediment is a significant factor influencing detachment and transport processes. However, the changeability variables of particle size distribution under different flow conditions have been less considered. Accordingly present study was therefore planned to evaluate the changes in particle size distribution of effective sediments by laser diffraction in initial unsteady and mature steady flow conditions in laboratory scale for a type of soil that was collected from Koudir region in Mazandaran Province. Towards this attempt, rainfall simulation experiments with intensities of 30, 60, and 90 mm h-1were conducted in a set of 1 × 6 m plot with varying slopes of 5, 15 and 25% based on governing condition in the north region of the a soil type and in three replications. The results showed that the sediment concentration is influenced by the slope more than by the rainfall intensity in runoff different conditions. In addition, the results explained significant levels of (p<0.05) for particle of 10 in slope of 5% and in rainfall intensities of 60 and 90 mm h-1 in steady and unsteady flow conditions. While particle of >2 micron had a significant different (p<0.05) in slope of 5% and in rainfall intensity of 30 mm h-1. In this regard, variable of D50 had very complex behavior in slopes and different rainfall intensities but D90 was not influenced by slopes and rainfall intensities in confidence level of 90% in steady and unsteady flow conditions because of inability flow in moving particles of >63 micron and especially variable of D90.
