Effect of varying the distance of collectors below a sprinkler head and travel speed on measurements of mean water depth and uniformity for a linear move irrigation sprinkler system

A series of sprinkler irrigation uniformity tests were conducted to determine the effect of collector height and speed on applied water depth and uniformity from a linear move sprinkler irrigation system. Collectors, 102 mm in diameter and 200 mm in height, were set in the field according to the method outlined by ASAE [(2001). American Society of Agricultural Engineers. Test procedure for determining the uniformity of water distribution of center pivot and lateral move irrigation machines equipped with spray or sprinkler nozzles. ASAE Standards, ANSI/ASAE S436.1 MAR01] test procedures. The sprinkler system used in the study was a fixed plate sprinkler head with a 180° wetting pattern. Catch devices were placed to 300, 600, 900, and 1200 mm heights above ground and tested with 15 and 30 m h−1 speeds. The results indicated that mean sprinkler irrigation depths ranged from 45.5 to 51.4 mm and from 21.3 to 25.9 mm for 15 and 30 m h−1 system speeds, respectively. Mean coefficient of uniformity (CU) values for the same speeds ranged from 89.4% to 92.6% and 88.9% to 95.1%, respectively. Both irrigation water depth and CU measurements were significantly affected (p<0.05) by collector height but halving the irrigation system speed, apart from producing the expected doubling in water depth, produced no significant effects. Differences in collector heights could cause differences in irrigation depth and CU values of as high as 10 mm and 6%, respectively.