Trickle Irrigation Systems Design Based on Emission and Crop Yield Uniformities.

Abstract: Trickle irrigation systems design is based on pre-established emission uniformity (EU) by combining equipment characteristics’ result and its hydraulic configuration; however, neither emission nor yield uniformity desired value is always confirmed by the end of the project in field conditions. This study aimed to evaluate the relationship between EU used in trickle irrigation system design and the final yield uniformity. The hypotheses were: a) trickle irrigation system EU is equal to the pre-established EU in its design when applied to field conditions; b) EU has always the lowest value when compared to other uniformity indicators; c) the discharge variation coefficient (DVC) is not equal to yield variation coefficient (YVC) in the subunit; and d) the difference between the DVC and YVC depends on the water depth applied. The uniformity indicators evaluated were: EU, distribution uniformity (UD), and the index proposed by Barragan et al. (2006); they were compared by estimating the performance of a trickle irrigation system applied in a citrus orchard with dimensions of 400 x 600m. The irrigation system design was optimized by a Linear Programming model. Three rows were leveled in the orchard’s larger direction and the spacing adopted was 7 x 4m. The manifold line operated on a slope condition. The sensitivity analysis involved different slopes 0, 3, 6, 9 and 12%, and different EU values 60, 70, 75, 80, 85, 90 and 94%. The citrus yield uniformity was evaluated by the variation coefficient. After the design the EU was sharper on the initial values (lower than 90%) compared to the pre established EU; it repetitive times generate lower values than the UD and indexes proposed by Barragan when uniformity was compared. The emitter variation coefficient was always lower than the productivity variation coefficient. To sum up, to obtain production uniformity, it is necessary to consider the irrigation system uniformity and mainly the water depth to be applied.

Keywords: linear programming, irrigated citrus, trickle irrigation.