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Chaudhary Charan Singh Haryana Agricultural University (1982)

Unsaturated hydraulic properties and cation exchange equilibria in soils of semi-arid and humid regions

Baruah, Tapan Chandra

Titre : Unsaturated hydraulic properties and cation exchange equilibria in soils of semi-arid and humid regions

Auteur : Baruah, Tapan Chandra

Université de soutenance : Chaudhary Charan Singh Haryana Agricultural University

Grade : Doctor of Philosophy (PhD) 1982

Résumé : KrishiPrabha (Indian Agricultural Doctoral Dissertations Repository)
Six surface soil samples, three from a semi-arid region (Haryana) -and the rest from a humid region (Assam) were collected for conducting water movement and cation exchange equilibria studies. Horizontal -absorption experiments were conducted in plexiglass columns in the laboratory for the determination of soil-water diffusivity D(Æ) and capillary conductivity K(Æ) functions. Scaled soil water diffusivity was calculated from, the data on D(Æ), surface tension (e), viscosity (h) and penetration coefficient (l). To predict soil moisture profiles both , in e homogeneous and layered soils, water transport equation was solved numerically. Unsaturated hydraulic conductivity was predicted by, at method based on pore size distribution, choosing the matching point near -saturation. There was a fair agreement between the observed and, predicted values of moisture profiles in homogeneous and layered soil columns as- well as unsaturated hydraulic conductivity.
Cation exchange equilibria studies involving ion pairs-Al3+ Ca2+, Al3+-K+ Al3+-NH4+, Ca2+-K+, Ca2+-NH4 and NH4+-K+ were conducted on three acid soils from Assam (Soils 4, 5 and 6) ; and Ca2+-K+, Ca2+-NH4+, Ca2+-Na+, NH4+-K+ and K+-Na+ on three normal soils from Haryaana (Soils 1, 2 and 3). These studies were conducted on homoionic soils at a total electrolyte concentration of 10 me l-1 r systems involving Al3+ and 50 me I-1 for rest of the systems. The results were analysed in terms of normalized exchange isotherms, selectivity coefficients and standard free energy change of the exchange reaction (Gºr). For soils of humid region Al3+ was preferred over Cal+. Preference was of the order : Soil 4> Soil 5> Soil 6. For Al3+ -K and Al3+-NH4+ systems, the preference was for K+/or NH4+ to Al3+ ; the order being : Soil 67 Soil 4 > Soil 5. This was explained on the basis of relative contents of diactahedral mica together with vermiculites and smectites. For Ca2+-K+ system, the values of the Gºr or suggested preference for K+. The values of Gapon (KG), Vanselow (Kv) and Krishtamoorthy-Davis-Overstress (KKDO) selectivity coefficients decreased with the increase in K+ saturation. NH4+ behaved similar to K+ in the Ca2+-NH4+ system.
The results on Ca2+-K+, Ca2+-NH4+ and NH4+-K+ systems in soils of semi and region were almost similar with those of soils of humid region. The results on cation exchange equilibria studies on normal soils of Haryana- showed preference for Ca2+ to Na4+. The values of KG, Kv and KKDO increased with the increase in Na4+ saturation. For K+- Na4+ system, the values of Gºr suggested a strong preference for K+ to Na4+.

KrishiPrabha (Indian Agricultural Doctoral Dissertations Repository)

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