Abstract
System evaluations were performed on 48 center pivots in different parts of Saudi Arabia. These systems, located on different farms in four different regions of the country, namely: Riyadh, Jouf, Qassim and Eastern regions, were evaluated to study the effect of lateral configuration on water application uniformity as regards the original vs. modified laterals. Lateral configuration modifications have been made by the local farmers through a chang of the position of the lateral and spray nozzles from the original design. Depths of water distribution along the lateral, Coefficient of uniformity (Cu) and Distribution uniformity of the low quarter (Du) were determined and compared for the original and modified laterals under field conditions. The average values of Cu for original systems ranged between 71.81 and 89.46% with an overall average of 82.69%, whereas the average values of Cu for modified systems rangingbetween 61.35 and 84.33% with an overall average of 78.05%. Also, the values of Du ranged between 54.14 and 81.81% with an overallaverage of 73.24% for the original systems, while these values for the modified systems ranging between 31.45 and 77.07% with an overall average of 66.87%. The results finally indicated that the values of uniformity for original vs. modified laterals were significantly different indicating that there existed a noticble adverse effect of center pivot lateral configuration on the uniformity of water application.