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Wyświetlanie 1-2 z 2
Tytuł:
Moisture dynamics as related to capillary and drainable pores in the Nile Delta soils
Autorzy:
Amer, A.M.
Powiązania:
https://bibliotekanauki.pl/articles/2083704.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
modelling unsaturated hydraulic conductivity
drainable and capillary pores
alluvial
clay and sandy soils
Opis:
The dynamic of soil moisture may be studied through water flux, storage, moisture conductivity and movement into the soil pore spaces. The volume of pore space in the soil and also the size, shape, type, continuity and distribution of the pores are important characteristics related to the storage, conductivity and movement of water and gases. The movement of water by gravitational forces in the natural soils occurs principally through the non-capillary pores (i.e. rapidly drained pores), while other movements occur in capillaries which may be classified as coarse and fine capillary pores. The unsaturated condition of soil water is a common state in nature after rainfall or as a result of irrigation, therefore, the purpose of this study was to develop equations to describe and estimate the unsaturated hydraulic conductivity K(θ) in relation to soil pore-size classes that contained the available water in the soil root zone. The equations were based on a water-retention curve, saturated hydraulic conductivity and pore-size function measured from undisturbed cores. The equations were applied to three soil profiles from the Nile Delta and compared with measured K(θ) data from two field experiments, which were conducted in clay in an unsaturated condition and in sandy soil areas using the internal drainage in situ method. The pore size function f(r) represents the fraction of the total pore whichvolume, which was contributed by pores with radii from 0 to ∞ at the prevailing degree of saturation. Data showed the applicability of the suggested equations for calculating unsaturated hydraulic conductivity in the soil pores even for soils with a high proportion of clay.
Źródło:
Acta Agrophysica; 2019, 26, 2; 29-43
1234-4125
Pojawia się w:
Acta Agrophysica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water table as a source for irrigation in the Nile Delta soils
Autorzy:
Amer, A.M.
Powiązania:
https://bibliotekanauki.pl/articles/2083572.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
Infiltration functions
water table
moistening of the root zone
steady sorptivity
hydraulic conductivity
capillary rise
Opis:
The purpose of this study is to predict the contribution of the water table in moistening the root zone using theoretical and empirical equations containing the parameters of evapotranspiration, crop factor, and capillary rise in relation to the hydrophysical properties of soil. Five alluvial (clay) soil profiles located at middle Nile Delta were investigated for the application of the assumed equations. Four areas of soils were cultivated with wheat and clover in the winter and maize in the summer, and citrus trees in 2014/2015 growing season. Soil samples from the investigated areas were subjected to chemical and physical analyses. Water table depths were determined using field piezometers in the same places where the soil samples were collected. The other hydro-physical parameters were estimated. It was found that the water table contributed 20-40% of the irrigation water applied to the root zone in winter and 20% or less during the summer in the studied soils areas. An equation was derived to estimate the sorptivity (S) under dry conditions and at steady state infiltration. It was observed that S is decreased from unsaturated state to steady-state infiltration by 23.1 to 45.7% in cultivated soils and to 55.2% in uncultivated soil. Infiltration functions were estimated. It was suggested that the sorptivity at the steady infiltration rate (steady sorptivity, Sw) may be used to predict the hydraulic conductivity and the basic infiltration rate Ib. The calculated values of Ib by Sw corresponded to those obtained by infiltration experiment. This confirmed the significance of steady Sw as a new functional infiltration parameter. Also, data showed that the values of K(θ) calculated by the proposed equations were in the common ranges for such soils. The equations used (models) related K(θ) to soil pore radius (r) which were in turn based on soil hydraulic data including water retention h(θ), field basic infiltration rate, water sorptivity (S) and the distribution density function f(r) of soil pore size. The steady Sw parameter was used in the prediction of the hydraulic conductivity K(θ) and the basic (steady) infiltration rate Ib. It was concluded that in winter the water table contributed 20-40% of irrigation water applied to the root zone and less than 20% during the summer in the studied soils areas. These values should be considered in calculating the crop water requirements.
Źródło:
Acta Agrophysica; 2019, 26, 1; 79-92
1234-4125
Pojawia się w:
Acta Agrophysica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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