الفهرس 
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Abstract
The study aimed to investigate the effect of drip irrigation system uniformity on crop yield and mathematically describe the relationship between them. The study included two variables which were four cultivated crops namely squash, cucumber, turnip and lettuce, and four operating pressure heads, 5, 10, 15, and 20 m of water. Changing operation head was expected to cause the required variation in uniformity parameters which included uniformity coefficient (UC), distribution uniformity (DU), emission uniformity (EU) and field manufacturing coefficient of variation (CVf).
Results indicated that the yield of all crops was proportional to drip irrigation system uniformity. This was reflected on water productivity which followed the same trend to be increased with the increase in drip irrigation system uniformity. Greatest values of crop yield were at 15 m operating head which showed the greatest level of uniformity with values of 20.90 Mg.ha-1, 13.48 Mg.ha-1, 8.97 Mg.ha-1 and 14.79 Mg.ha-1 for Squash, Cucumber, Lettuce and Turnip, respectively. Greatest values of energy use efficiency were at 5 m operating head which showed the lowest uniformity indices. Correlation coefficient (r) value has been calculated basing on uniformity parameter as independent variable and crop yield as dependent variable. Mathematical models of the relationship between crop yield and EU were developed. All the models took the form of power function. The study recommended the use of EU as a uniformity parameter for future modeling studies of the relationship between crop yield and drip irrigation system uniformity.