%0 Journal Article
%T Water Quality Effect on Plant-Available Water and Pore Size Distribution of Two Texturally-Different Calcareous Soils
%A M. Khatar
%A M. R. Mosaddeghi
%A A. A. Mahboubi
%J Journal of Science and Technology of Agriculture and Natural Resources
%D 2012
%I Isfahan University of Technology
%X This study was conducted to investigate the effect of water salinity and sodicity on pore size distribution and plant-available water of two clay and sandy clay loam calcareous soils. All combinations of water EC values of 0.5, 2, 4 and 8 dS m-1 and SAR values of 1, 5, 13 and 18 (in total 16 solutions) were used to wet and dry the soil samples for five cycles. Then, water retention of the soil cores was measured at matric suctions of 0 (¦Ès), 10 (¦È10) 100 or 300 cm (¦ÈFC) and 15000 cm (¦ÈPWP). The following quantities were calculated: the difference between ¦È100 or ¦È300 and ¦È15000 considered as available water contrent, the ¦Ès and ¦È10 as macrorosity, the ¦È10 and ¦È100 as mesoporosity, and the ¦È100 as microrosity. The initial porosity of both soils was similar, but the greater values of pore indices and ¦ÈFC, ¦ÈPWP and AWC were measured in the clay soil due to clay swelling. As water EC increased, mesopores were destructed and altered to macropores and micropores. Salinity altered the mesopores into macropores due to contraction of diffuse double layer and particle¡¯s flocculation and consequently decreased the ¦ÈFC, and created new micropores which were responsible for the higher value of ¦ÈPWP. These trends ultimately diminished the AWC. As water SAR increased, mesopores were destructed and altered to micropores but it did not significantly affect the macropores. With increment of SAR, both ¦ÈFC and ¦ÈPWP increased due to structural distruption clay swelling and dispersion resulting in increased adsorptive and interlayer surfaces. The increasing effect of SAR on ¦ÈPWP was greater and more distinct so that AWC was reduced. As a result, high values of SAR of irrigation water decreased the soil available water to plants besides its toxicity and hazardous effect on plants. With increment of irrigation water salinity, the destructive impacts of SAR diminished. The influence of water quality on water retention was pronounced for the clay soil.
%K Soil porosity
%K Water quality
%K Field capacity
%K Permanent wilting point
%K Available water content
%K Diffuse double layer
%U http://jstnar.iut.ac.ir/browse.php?a_code=A-10-573-3&slc_lang=en&sid=1