Spatial information about soils generally results from local observations which are destructive and time consuming. Geophysical techniques could help soil mapping since they are non-destructive and fast. Electrical resistivity is interesting for soil studies due to a wide range of values and as it depends on soil characteristics. This work aims to study soil spatial variability using electrical resistivity. GPS defined grid points of 40X40 m were installed in the experimental western farm (EWF) in the Faculty of Agriculture of Cairo University in Giza. Electrical resistivity was measured at 40 points using 4-electrodes Wenner array in a line perpendicular to the path direction. Soil resistivity data from 2depths profiling mode was considered to produce two apparent resistivity maps and geostatistically tested. Soil resistivity taxa were sampled and analyzed for soil moisture, EC and bulk density. Krigged soil resistivity maps were produced for depths (i.e. 30 and 60 cm). Kriging and Semivariogram interpretation was conducted, and the spatial dependency of top and subsoil resistivity were moderate (48.4% and 68.6% respectively). Highly significant negative correlations were recorded in the topsoil between apparent or true resistivity and soil moisture, EC or bulk density. The obtained models were used to produce conjugated moisture and EC maps and geostatistically investigated. The spatial dependency of the top and subsoil moisture or salinity were moderate. Soil moisture and EC are the most significant factors for controlling soil electrical resistivity. The method used opens the way to the development of semi-automatic soil mapping from electrical resistivity data.
Sandy soils are of a wide occurrence under arid and semiarid regions. Most of Libyan soils are sandy soils.Twenty two soil samples were chosen from the western coastal strip of Libya representing a wide range variation of sand fractions were chosen for this study. Different chemical and physical properties were determined, including particle size distribution, bulk density, retention moisture characteristics and saturated hydraulic conductivity. Available water content was determined using moisture retention data. The available water content obtained were affected mainly by the percentage of silt + clay. These effect was decreased by increasing the diameter of the soil fractions. The empirical equation between the available water content and the silt + clay, can be used in water management practices of the sandy soils.
Rice (Oryza sativa. L) is considered one of the most important food crops, as it is a more profitable one than the other summer crops from the economical point of view in Egypt. Also, it is not only stable food source for majority of the Egyptian population but also it has become one of the most exportable crops in Egyptian agricultural system after the free cropping pattern policy. For these reasons, the areas cultivated with rice have been annually increased, although it is one of the most inefficient in water use among field crops due to it grows generally under continuously submerged conditions. Under the key of saving water conditions and achieving high water use efficiency, a special attention was focused to optimize transplanting method and irrigation water management for raising the water use efficiency of rice plants through a proper their equitably distribution among all rice fields. Thus, the problem is how to distribute the irrigation water equitably among all rice fields with high water use efficiency?.To achieve a profitable solution for this problem, a field experiment was conducted on a sandy clay loam soil during two successive growing summer seasons 2007 and 2008 at a private farm, Sinnuris district, Fayoum governorate, Egypt to evaluate the effect of applying a new method (M) for rice transplanting (transplanting on strips) on rice yield and its components as well as some soilwater relationships. However, rice seedlings of two rice cultivars of Hybrid 2 and Sakha 104 were transplanting at furrow bottoms of either 60 cm (M 2 ) or 80 cm (M 3 ) apart as compared with the traditional transplanting method (M 1 , transplanting on a flat soil), under different submerged irrigation water depths of 6 cm (D 1 ) and 8 cm (D 2 ).The obtained data indicate that highly significant differences were existed among the studied transplanting methods, among some plant parameters of growth (i.e., plant height) and rice yield (i.e., panicle length, 1000 grain weight, grain and straw yields). These differences are confirmed by the mean values in combined analysis for the plant heights which recorded 100.30, 105.18 and 107.12 cm for M 1 , M 2 and M 3 treatments, respectively. Also, the tallest rice plants were significantly affected by both rice cultivars and submerged irrigation water depths, where plant height was recorded 107.1 cm at a depth of 8 cm (D 2 ) for Hybrid 2 cultivar as compared with Sakha 104 which was 101.3 cm as an average of the two growing seasons.Results showed also a significantly increase in panicle length due applying the new transplanting method, where its mean value in combined analysis were 19.56, 20.93 and 21.71 cm for M 1 , M 2 and M 3 , with a superiority for D 2 (8 cm depth) and Hybrid 2 cultivar as compared with D 1 (6 cm) and Sakha 104, respectively. Also, the corresponding mean values were 26.13, 28.71 and 29.25 gm for 1000 grain weight of rice vs 26.53 and 29.53 gm for submerged irrigation water depths of D 1 (6 cm) and D 2 (8 cm), respectively.
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