| Titles |
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English :
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Using simple mathematical functions of
some easily measured physical properties of the Nile alluvial soils for calculating the unsaturated hydraulic conductivity
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Arabic :
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إستخدام الدالات الرياضية البسيطة لبعض الخواص الفيزيائية سهلة التقدير فى الأراضى النهرية الرسوبية لحساب التوصيل الهيدروليكى غير المشبع
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| Abstract |
The Nile alluvial soils of Egypt are considered the main resource of agricultural utilization. Therefore, knowledge concerning the factors controlling their productivity, particularly those affecting water movement in the unsaturated flow at the plant root zone, is of the importance in planning for soil-water management practices under the different irrigation and drainage systems as well as in monitoring the movement of pollutants and maximizing the nutrients supplying power capacity of soil.
In this work, fourty surface soil samples (0-35 cm) were chosen from the Nile Valley and Delta of Egypt (i.e., Beni Suef, El Fayoum, Giza and El Monufyia Governorates) to represent a wide range of soil texture and structure grades. The different textural grades of selected soil samples are of clay, clay loam, sandy clay loam and sandy loam as well as they are all non-saline and non-sodic since their ECe and ESP values are < 4 dS/m and < 15, respectively. Thus, the current work aimed at identifying the more effective and contributed to soil physical properties, particularly to unsaturated flow in such soils. Also, using the quantitatively functions of these properties for calculating the Kθ values will be a matter of course in this study.
The obtained results show a relative high Kθ value in the relatively coarse textured soils at lower tension levels of 0.10-0.66 atm as compared to the clayey and clay loam ones, since the removal water filled pores at these low tensions is more less directly related to capillary potential as well as soil structure parameters (aggregate and pore size distributions). The reverse was true at the higher tensions (1.0-15.0 atm), due to Kθ tended to decrease rapidly in the relatively coarse textured soils, while it maintains in the fine and medium ones. The later condition is expected since the swelling of expanded soil mechanical fractions (silt and clay) lead to increase the conductive pores for the unsaturated water flow, however, the conductivity capacity of the relatively coarse textured soils drops off sharply once the continuous system of water filled-small pores is broken. This condition causes a less amount of water able to move from points of low tension towards those of high ones. These adverse conditions are more affected by matric potential of the fine textured soils that exerted by the soil force of retention. This means that the relationship between Kθ values and soil texture grades is reversed, however, in the dry conditions the fine and medium textured soils are likely to have higher Kθ values than the relatively coarse textured ones. Also, this behaviour is logic; since a relatively high percentage of macro-pores (inter-aggregate porosity) of the coarse textured soils govern the unsaturated flow conditions vs a high percentage of micro ones (intro-aggregate porosity) in the fine and medium textured ones.
It is noteworthy that the values of contribution percentages of the easily measured soil physical properties, i.e., soil texture (soil mechanical fractions) and soil structure (aggregate and pore size distributions) are considered good criteria or inputs for calculating the unsaturated hydraulic conductivity (Kθ). This is mainly due to these parameters are responsible for creating the paths that govern the water movement in the unsaturated conditions. Consequently, the laboratory measurements of these physical properties are a good task for studying the unsaturated flow and calculating the Kθ values under the different tension levels. Thus, the final goal of this work was achieved by executing or proposing simple mathematical models for calculating Kθ among the variable soil wetness and tension levels for the Nile alluvial soils, depending upon the more easily measured and contributing soil physical properties. Executing such models is of simplicity when compared with such method of soil retention curves under a wide range of soil tensions that are characterized by complicated, difficulty and costly steps
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| Publication year |
2006
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| Pages |
226-240
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| Availability location |
Soils, Water and Environment Research Institute, ARC, 9 Cairo Univ. St., Giza, Egypt
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| Availability number |
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| Organization Name |
Soil, Water and Environment Research Institute (SWERI)
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| City |
Zagazig
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| serial title |
Egyptian Journal of Applied Sciences
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| ISSN |
1110-1571
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| Author(s) from ARC |
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| External authors (outside ARC) |
محسن عبد الحميد محمد البسيونى
قسم الاراضى والمياة- كلية الزراعة - جامعة الفيوم
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AGROVOC
TERMS |
Alluvial soils.
Chemicophysical properties.
Measurement.
Permeability.
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| Publication Type |
Journal
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