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Downward water flow in the vadose zone occurs principally through the non-capillary pores, while the redistribution and lateral and upward flow occurs in the capillary pores. The purpose of this study was to propose equations to estimate water flow, Q(θ), and hydraulic conductivity, K(θ), in the capillary and non-capillary soil pores. The equations related K(θ) to soil pore radius (r) were based on soil hydraulic data, including water retention h(q), field basic infiltration rate, water sorptivity (S) and distribution density function f(r) of the soil pore size. Calcareous sandy loam and alluvial clay soils located at the Nile Delta were used to test the validity of the assumed equations. Data showed that the values of K(θ) calculated by the proposed equations were in the common ranges for such soils. The equations are therefore expected to be applicable for both coarse and fine textured soils. Also, an equation was derived to estimate the sorptivity at steady state infiltration. It was observed that S is decreased in going from the un-saturation condition to steady state infiltration by 15.1% and 45.9% in sandy loam and clay soils, respectively.

Water infiltration and storage under surface irrigation are evaluated, based on the initial soil water content and inflow rate as well as on the irrigation parameters and efficiencies. For that purpose, a field experiment was conducted using fruitful grape grown in alluvial clay soil at Shebin El-Kom in 2008 grape season. To evaluate the water storage and distribution under partially wetted furrow irrigation in comparison to the traditional border irrigation as a control method, two irrigation treatments were applied. They are known as wet (WT) and dry (DT) treatments, at which water was applied when the available soil water (ASW) reached 65% and 50%, respectively. The coefficient of variation (CV) was 6.2 and 10.2% for WT and DT respectively under the furrow irrigation system as compared to 8.5% in border. Water was deeply percolated as 11.9 and 18.9% for wet and dry furrow treatments respectively, as compared with 11.1% for control with no deficit. The application efficiency achieved was 86.2% for wet furrow irrigation achieving a high grape yield (30.7 t/ha). The relation between the infiltration (cumulative depth, Z and rate, I) and opportunity time (t₀) in minutes for WT and DT treatments was: Z_WT = 0.528 t₀^0.6, Z_DT = 1.2 t₀^0.501, I_WT = 19 t₀^–0.4, I_DT = 36 t₀^–0.498. Also, empirical power form equations were obtained for the measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion, and recession.

Six calcareous and alluvial soil profiles differing in their texture, CaCO3 and salinity were chosen from west and middle Nile Delta for the present study. The 1 st and 2 nd profiles from Borg El-Arab area were sandy loam in texture and > 30% CaCO3, while the 3 rd and 4 th profiles (from Nubaria area) were sandy clay loam and < 30% CaCO3. The 2 nd and 4 th profiles were taken from cultivated area with maize. The 5 th profile from Epshan area was non-saline clay alluvial soil and the 6 th from El-Khamsen was saline clay alluvial soil. The relation between soil moisture content (W%) and water vapour pressure (P/Po) was established for the mentioned soils. Data showed that the specific surface area (S) values were 34-53 and 44-60 m 2 /g for calcareous soils of Borg El-Arab and Nubaria areas, 206-219 and 206-249 m 2 /g for non-saline and saline clay alluvial soils of Epshan and El-Khamsen areas, respectively. The corresponding values of the external specific surface area (Se) were 16-21, 14-22, 72-86 and 92-112 m 2 /g. Submitting Wm + Wme as an adsorption boundary of moisture films (Wc) (where Wm is mono-adsorbed layer of water vapour on soil particles and Wme is the external mono-adsorbed layer), the maximum water adsorption capacity (Wa) was found to be Wc + Wme or Wm + 2Wme. It was ranged from 1.88 to 2.70%, 1.97 to 2.95%, 9.70-10.70% and 10.80 to 13.12% while the maximum hygroscopic water (MH) values were 2.43-3.78%, 2.91-4.65%, 16-17% and 18.30-21.9% for the studied soil profiles respectively. The residual moisture content (θr) at pF 7 and P/Po = 0 was ranged from 0.0005-0.0010%, 0.0007-0.0019% and 0.0043-0.0048% in Borg El-Arab, Nubaria and Epshan soil profiles, respectively. The inter-relations between the surface area and the hygroscopic moisture parameters of the soils under investigation were as follows: Calcareous soils; Wm = 0.40 MH, Wc = 0.55 MH, Wa = 0.70MH, S = 14 MH Non-saline soil; Wm = 0.35 MH, Wc = 0.49 MH, Wa = 0.63 MH, S = 13 MH Saline soil; Wm = 031 MH, Wc = 0.45 MH, Wa = 0.59 MH, S = 12 MH These relations give possibility to deduce the soil moisture adsorption capacities and specific surface area via maximum hygroscopic water, which can be obtained through the experimental determination of water vapor adsorption isotherms.

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