الفهرس 
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Abstract
The aim of this work is to study the direction of soil moisture soil water behavior in sandy soil profile, to optimize irrigation water management to save the irrigation water and minimize the losses. br This done by using neutron scattering technique and soil moisture retention curve model for different soil layers, -#119;-#104;-#101;-#114;-#101; neutron scattering meter was used to detect soil water after and before next irrigation, to determine soil moisture depletion which happened during irrigation interval in active root depth, also van Genuchten (1980) model for water retention after estimate the equation parameters , m, and n. br Therefore it is possible to predict soil moisture tension at different moisture content after and before irrigation, as for it is possible to determine total hydraulic potential witch equal soil matric suction plus gravitational potential. br By knowing total hydraulic potential through soil profile up to active root depth it is possible to determine the losses of soil water by evaporation, water uptake by plant roots and deep percolation (under active root depth). br Three treatment of organic manure were done control (sand soil), 20m3 and 30m3 was added to the soil surface layer (0-15 cm) beside three irrigation intervals. br Onion was planted under drip irrigation system, to studies the water distribution around the drippers, also between the laterals, four access tubes were installed around the dripper close the distance of 12.5cm around the dripper and the fifth was installed adjacent to the dripper, these access tubes used for neutron scattering meter. The results can summarized in this points br - Neutron scattering technique and soil moisture retention curve model helps more to study the water behavior in the soil profile. br - It was Possible to predict the active root for water absorption, and thus the soil layer which are present the active root for water absorbing, it is very useful for studying water movement and nutrients in soil . br - Irrigation to field capacity helps to minimize the losses by deep percolation. br - Active root depth helps to divide the water depletion into two components the first one is due to the effect of evapotranspiration and the other is by gravity force. br - Detecting soil moisture by neutron scattering meter helps to determine the total hydraulic potential in active root depth. Also can helps to detect the direction of water movement in soil profile. br By using neutron scattering meter, moisture retention curve model and surfer program, it is possible to study the movement of soil water vertically and horizontally around the dripper. br Animal manure helps to increase the soil water content in the available range -#102;-#114;-#111;-#109; (0.1 to 15 bar). br The addition of animal manure and irrigation to br field capacity can maximize the water use efficiency and minimize the water deep percolation, which was 0 mm/day in some treatments. br The best irrigation interval under the conditions of this study to onion plant is 5 days with rate2 of organic manure. br Constants of van Genuchten (1980) model are affected by the animal manure addition; parameter ”” were 1.825, 1.191 and 0.0712 for control, rate 1 and rate 2 respectively , while parameter ”n” were 1.662, 1.492 and 1.508 for control, rate 1 and rate 2 respectively.