CALCULATION OF SOIL WATER DIFFUSIVITY USING A MODEL FOR SOIL MOISTURE PROFILE UNDER DIFFERENT SALINITY CONDITIONS
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Abstract
A closed formed model modified from that of van Genuchten (1980) was used to fit
the data of soil moisture profile ( θ vs. λ ) from which the slope dλ/dθ can be evaluated
and then the soil water diffusivity [D(θ)] can be calculated. Diffusivity was calculated for three soil textures under different salinity conditions.
The results showed that the model fitted the data very well with 1% confidence level (R2 > 0.93). D(θ) increased sharply with soil moisture for all soils but its values were lower when the texture got finer. At a certain sodium adsorption ratio (SAR), D(θ)
increase with the increase of salt concentration (C) of the water infiltrating. Increasing SAR of water caused a decrease in D(θ) at any level of C. Same trends were obtained for the values of weighted mean diffusivity D .
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References
Al-Douri, N. T. (2002) Evaluation of water transport functions in soil treated with fuel oil. Ph. D. Dissertation, College of agriculture, University of Baghdad, Iraq (In Arabic).
Aoda, M. I. (1982) Critical assessment of the Green and Ampt water infiltration equation. Ph. D. Dissertation, University of Nebraska, Lincoln,
NE, USA.
Aoda, M. I.; D. R. Nedawi; and I. A. Abdel-Rassul (1993) Salts effects on water transport functions in an unsaturated soil. Iraqi J. Agric Sci. 24(1):20-29.
Aoda, M. I. ; A. H. Thiab ; and N. T. Mahdi (2005) Approaches to estimate the suction head at the wet front in the Green and Ampt water nfiltration equation, J. Engineering, College of Engineering, University of Baghdad, Iraq: 11(4): 775-785.
Bruce, R. P. and A. Klute (1956) The measurement of soil water diffusivity. Soil Ser. Soc. Am. Proc. 20:458-462.
Childs, E.C. and G. N. Collis –George (1950) The permeability of porous materials. Proc. Ray. Soc. London ser A 201:392-405.
Crank, J. (1956) The mathematics of diffusion. 1st ed. Oxford Univ. press. London
Dirksen, C(1975) Determination of soil water diffusivity by sorptivity measurement. Soil Sci. Soc. Am. Proc. 39:22-27.
Gardner, W. R. (1962) Note on the separation and solution of diffusion type equation. Soil Sci. Soc. Am. Proc. 33:404-408.
Gardner, W. R. and M. S. Mayhugh. (1958) Solutions and tests for the diffusion equation for the movement of water in soil. Soil. Sci. Soc. Am, Proc. 22:197-201.
Hillel, D. (1980) Applications of soil physics. Academic press, p.18.
Klute, A. et al. (1986) Methods of soil analysis: physical and mineralogical methods (2nd ed.) Agronomy 9(1). Am. Soc. Agron. Inc. Publisher. Madison, WI, USA.
Kulte, A. and C. Dirksen (1986) Hydraulic conductivity and diffusivity: Laboratory method. In Klute, A. et al. (1986) Methods of soil analysis: physical and mineralogical methods (2nd ed.) Agronomy 9(1):687-734. Am. Soc. Agron. Inc. Publisher. Madison, WI, USA.
Nofziger, D. L. and D. Swartzendruber (1976) Water content and bulk density during wetting of bentonite-silt columns. Soil Sci. Soc. Am. J. 40:345-348.
Page, A. L. et al (1982) Methods of soil analysis: Chemical and microbiogical Properties (2nd ed.) Am. Soc. Agron, Inc. publisher, Madison, WI, USA.
Philip, J.R (1957) The theory of infiltration 1. The infiltration equation and its solution. Soil Sci. 83:345-357.
van Duin, R. H. A.(1955) Tillage in relation to rainfall intensity and infiltration capacity of soil. Neth. J. Agric. Sci. 3:183-191.
van Genuchten, M. T. (1980) A closed – form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J. 44:892 – 898.
Whisler, F. D.; A. Kulte and D.B. Peters (1968) Soil water diffusivity from horizontal infiltration. Soil Sci. Soc. Am. Proc. 32:6 – 11.
Younan, T.F. (2008) Effects of salinity and Sodicity of irrigation water on the hydraulic properties of different textured soils. Ph. D. Dissertation, College of Agriculture, University of Baghdad, Iraq (In Arabic).