Erian, Wadid 
  
the soil using Collin’s Calcimeter, (Nelson, 1982). Gypsum content was determined using acetone according to (Black, 
1982; Hesse, 1971). The electrical conductivity of the saturated soil extract was carried out according to (Rhoades, 
1982). 100 undisturbed samples were collected from the same locations in cores with the dimensions of 2.5-cm length 
and 5 cm diameter. These were meant for studying the moisture retention at field capacity, permanent wilting 
percentage and interval points, by the pressure membrane apparatus, Klute (1986). 
2.2.2 The rating values for effective soil depth, after, (Erian et al., 1991 and Erian et al , 1996) and could be presented 
as follows: 
The effective soil depth classes: 
— . The very deep soils (d1: more than 120 cm). 
— . The deep soils (d2: between 90 — 120 cm depth from the soil surface), and 
— The moderate deep soils (d3: between 60 — 90 cm depth from the soil surface), 
— . The shallow soils (d4: between 30 — 60 cm depth from the soil surface), 
— The very shallow soils (dS: less than 30 cm), 
The soil salinity classes are calculated as an average of the EC (1:1) within 80 cm: 
— The non-saline soils (z1: less than 2 dS/m). 
— The slightly saline soils (z2: 2 - 4 dS/m), and 
— The moderately saline soils (Z3: between 4 - 8 dS/m), 
— . The strongly saline soils (z4: between 8 — 16 dS/m), 
— The very strong saline soils (z5: more than 16 dS/m), 
The drought classes: 
The studied area depends on flooding irrigation with intervals of irrigation: 14 days are without irrigation and seven 
days of irrigation in both Winter and Summer times. In most cases, the farmer is only allowed for one-day irrigation 
every 21 days. Accordingly the following classes were identified: 
— The very high moisture availability soils (m1: more than 21 days between irrigation before soil drying), 
— . The high moisture availability soils (m2: between 18 - 21 days between irrigation before soil drying), 
— . The moderately moisture availability soils (m3: between 14-17 days between irrigation before soil drying), 
—  Thelow moisture availability soils (m4: 10 - 13 days between irrigation before soil drying), and 
— The very low moisture availability soils (m5: less than 10 days between irrigation before soil drying). 
2.2.3. Geo-statistics offers methods for interpolation and analysis of spatial structure and the ability to provide risk- 
qualified predictors of exceeding threshold values is an indispensable tool for environmental decision-making. Kriging 
can be seen as a point interpolation, which requires a point map as input, has been used as the main technique for geo- 
statistical analysis. The ILWIS (2.2), ordinary Kriging algorithm was applied to delineate the most accurate purified 
boundaries for the different land qualities. In order to obtain a semi-variogram model for the data represents, the 
effective soil depths, soil salinity, and drought, the sill, the range and the nugget for each land quality were estimated 
and presented in a fitting curve. The sill represents the maximum level of the semi-variance, the range represents the lag 
at which the sill is reached, and the nugget represents intercept of the variance. The weight factors are averaged input 
point values, similar to the moving average operation. The weight factors in Kriging are determined by using user- 
specified semi-variogram model parameters that based on the output of the spatial correlation operation. The 
distribution of input points, and are calculated in such a way that they minimize the estimation error in each output 
pixel. The estimated or predicted values are thus a linear combination of the input values, Stein (1998). The geo- 
statistical analysis is a two-step-procedure. The first step is the calculation of the experimental semi-variogram and 
fitting a model; and the second is the interpolation to study the spatial variability of soil properties. 
The formulae of each model as follow: 
The Spherical Model Formulae is: y(h) = Co + C * [(3h / 2a) — (h’/22%)] 
Where: vis the estimated value ais the Range parameter 
h is the distance Cis the Sill parameter Co is the Nugget parameter 
The crossing technique was applied to identify the current land capability of the studied area. 
2.2.4 For statistical analysis the information about settlement, income and different crops production are given in 
Tables (1), after the Social and economical data of 1998 survey of the Sustainable Integrated Development and 
Environmental Sector of Caritas (SIDES, 1999). The survey was implemented under the authors supervision and in 
cooperation with CAPMAS (The Central Agency for Puplic Mobilization and Statistics), license no. 624/1998 
published in El-Wakaa El Masria, issue no. 290 on 20 December 1998, covering Sugar Beet area (35 villages), 
Nubariya, Egypt. 
2.2.5 The flowchart of the study is modified after, (Erian & Yacoub, 1999), and presented in Figure (2) 
  
406 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.