Sprinkler lateral spacing impacts on field distribution uniformity of precipitation and carrot yield

摘要

The majority of production vegetables in California are irrigated with hand-move aluminum sprinkler pipe 'solid-set' in laterals up to 400 m long with distances of 9.1 to 15.2 m between each lateral; 12.2 to 13.7 m being most common. The impact of seven different sprinkler lateral spacings (10.1 to 14.6 m) on irrigation distribution uniformity (DU) and carrot yield was evaluated in three different carrot plantings. Sprinklers were 1, 2, and 3 to 5 years old for the first, second and third plantings, respectively. The distribution of sprinkler precipitation was found to change from Gaussian to random as sprinkler spacing increased. Mean sprinkler precipitation DU's (as measured with periodic catchcan evaluations) varied from a low of 71.8 percent for a 13.7 m spacing with the 3+ year old sprinklers to a high of 86.0 percent for the 14.2 m spacing with new sprinklers. A "seasonal mean normalized DU" was calculated to estimate the uniformity of precipitation for the whole season. This value accountsfor wind shifts in the precipitation pattern from one sprinkler evaluation to another. The result is a general increase of 4 to 8 percent in seasonal DU over the simple mean of DU's from multiple evaluations. This seasonal DU (from a low of 81.6 to a high of 90.8 percent) is more consistent with the DU of total root yield (81.5 to 89.3 percent). There was no significant correlation between lateral spacing and mean DU (r~2 = 0.001), seasonal normalized DU (r~2 = 0.184), or carrot yield (r~2 = 0.028).