Impact of treated sewage sludge application on phosphorus release kinetics in some calcareous soils |
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| Authors: | Alireza Hosseinpur Hamed Pashamokhtari |
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| Institution: | (1) Department of Soil Science, College of Agriculture, Shahrekord University, Shahrekord, Iran;(2) Department of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamadan, Iran |
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| Abstract: | Treated sewage sludge contains significant amount of phosphorus and is widely used in agriculture. Kinetics of P release in
soils is a subject of importance in soil and environmental sciences. There are few studies about P release kinetics in treated
sewage sludge amended soils. For this purpose, sludge was mixed with ten soils at a rate equivalent to 100 Mg sludge ha−1, and P desorption was determined by successive extraction using 0.01 M CaCl2 over a period of 65 days at 25 ± 1°C. Phosphorus release rate was rapid at first (until about first 360 h) and then became
slower until equilibrium was approached. Average of P released within 360 h for the unamended and amended soils was about
65 and 73% of the total desorbed P, respectively. Zero-order, first-order, second-order, power function, simplified Elovich
and parabolic diffusion law kinetics models were used to describe P release. First-order, Elovich, power function and parabolic
diffusion models could well describe P release in the unamended and amended soils. Correlation coefficients between P release
rate parameters and selected soil properties showed that in the control soils, calcium carbonate equivalent and Olsen-extractable
P; and in the amended soils, calcium carbonate equivalent, cation exchange capacity, organic matter and Olsen-extractable
P were significantly correlated with P release parameters. The results of this study showed that application of sewage sludge
can change P release characteristics of soils and increase P in runoff. |
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| Keywords: | Calcareous soils Phosphorus Sewage sludge Release kinetics Iran |
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