Morais, Julio Terencio da Silva,1960-(The University of Arizona., 1986)
Two separate field studies were conducted at the University of Arizona Campus Agricultural center in Tucson in the summer of 1985. The purpose of the first study was to use Infrared Theomometry, Micro Lysimeter, and Neutron Surface Meter Methods to estimate bare-soil water evaporation surrounding a point source emitter. The purpose of the second study was to estimate soil water infiltration from a point source using a theoretical model. In the model it is assumed that the water content ahead the front after infiltration commences is the same as the antecedent moisture content, and the moisture content behind the front is given by a quasi-linear solution that assumes an exponential relationship between the unsaturated hydraulic conductivity and the pressure head. The results from the first study showed good agreement among methods as indicated by high correlations. Also the results for the second experiment indicated that the model can be used to estimate infiltration from a point source, but special attention should be given to emitter flow rate.
Ahmed, Abdulkadir Sh. Ali,1955-(The University of Arizona., 1986)
Physical properties of texture, bulk density, saturated hydraulic conductivity, moisture characteristic curve and unsaturated hydraulic conductivity, expressed as relative K were determined for 25 bulk samples and 66 undisturbed soil cores collected from the University of Arizona Maricopa Agricultural Center. The CV values were evaluated for all parameters studied and their ranges were all found to be in agreement with the guidelines of Warrick and Nielsen (1980). Empirical models were used for calculation of saturated K moisture characteristics and unsaturated K. The calculated data were compared with the experimental data except for the unsaturated K for which experimental data were not available. A close agreement was found between the experimental and calculated data for the moisture characteristics data. However generalized conclusions were not obtained for the comparison for the saturated K nor for the moisture characteristic curves.
Amer, Saud Abdulaziz, 1953-(The University of Arizona., 1987)
Salt-affected soils have undermined the effectiveness of agricultural development of considerable areas of the world, especially in the arid and semi-arid regions. This research is set out for the direct measurement of salt-affected soil. Two experiments were conducted to study the influence of different salt types and concentrations on spectral reflectance of soil. In the first experiment, five different salts (Na₂SO₄, NaHCO₃, CaCO₃, CaCl₂ and NaCl) were mixed individually with Gila soil at 0.51, 1.51 and 3.0% by weight. The second experiment was conducted to examine the spectral response of sodium sulfate and sodium bicarbonate (individually and in combination) in Gila soil at 3.0 and 6.0% by weight. Reflectance measurements were made over all soil treatments under different moisture conditions. Upon drying (24-hour after wetting), different salt types and concentrations showed different spectral response. The chemical analysis of soil samples have indicated some important relationships which influenced, directly and indirectly, the spectral reflectance of soil surfaces.
The data of 14 soils were used to compute the ion activity product (IAP), the ratio of the ion activity product and to the solubility product (Ksp) of the pure minerals (IAP/Ksp) and to estimate the solid activity coefficients (SAC) of the soil components. The value of IAP and SAC of AlPO4 differs from soil to soil and increases with increasing P added to soil in acid soils and for calcium phosphate in basic soils. Magnesium apparently did not cause P adsorption or precipitation in the soils studied. The SAC of aluminum phosphate ranged from 10 to 10000 in acid soils. The mole fraction of the total phosphate in soil seemed to be a more satisfactory basis for calculating the concentration of the solid phase than was measurements of the available phosphate.
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