الفهرس 
REVIEW OF LITERATURESOnly 14 pages are availabe for public view
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Abstract
According to the constant and limited water resources in Egypt, besides, the expected climate changes and the continuous increasing population, therefore, water should be utilized as a rare commodity. This can be achieved through a lot of procedures that can all lead to lessen water consumption by plant and maximize irrigation water use efficiency. In other words; to obtain the best productivity from a water unit.
Adjusting water quantities given to plant via probes or tensiometers measure the soil moisture content and connected to control valves is one of the modern irrigation management methods. Using meteorological data accessed to special software programs, i.e., CROPWAT to calculate ETC, allow passing the net irrigation needs to the crop at certain soil moisture depletion point, is more developed irrigation management practice.Testing the onion crop under deficit irrigation 100, 70 and 40% under surface and subsurface drip irrigation methods in Wadi El Natroon Research station which represent the dry climate with sandy soil.
The experiment included:-
A. Two methods to estimate the irrigation requirements for onion included:
1. CROPWAT Program using to Calculating of water requirements, using the records of the Central Laboratory of Agricultural Climate (CLAC), The traditional method of water requirement FAO for calculating water requirement.
2. A developed criteria which represented by Arafa(2008).Effect of treatments on plants
The following parameters were studied:
1. Total yield per area.
2. Total dry weight
3. Total dry weight of bulbs
4. Total dry weight of leaves
5. Water use efficiency (kg / m3)
6. Bulb sizing
The main results in this study could be summarized in the following:
1) Using A developed criteria saved water and had founded highest values of biological yield in it compared to using FAO.
2) Possibility of benefiting from meteorological station and stored data for multiple purposes .i.e, adjusting the irrigation water needs of the plant according to the growth stage.
3) Using Surface drip irrigation system was the best when using a developed criteria compared to using subsurface drip irrigation system .
4) The tendency of water distribution and its average content in the soil profile increase relevant to the irrigation under the a developed criteria when comparing the average contents of water in the profile for all the cases of irrigation treatment.
5) Increase water use efficiency under a developed criteria compared to FAO.
6) High onion yield in its weight and quality too when using developed criteriawith surface drip irrigation comparing with CROPWAT 8.