Effects of drip irrigation circuit design and lateral line lengths: I—On pressure and friction loss

Laboratory tests were conducted at the Irrigation Devices and Equipment’s Test Laboratory, Agricultural Engineering Research Institute, Agriculture Research Center, Giza, Egypt. The experimental design of laboratory experiments was split in randomized complete block design with three replicates. Laboratory tests carried out on three irrigation lateral lines of 40, 60, 80 m under the following three drip irrigation circuit (DIC) designs; 1) one manifold for lateral lines or closed circuits with one manifold of drip irrigation system (CM1DIS); 2) closed circuits with two manifolds for lateral lines (CM2DIS), and 3) traditional drip irrigation system (TDIS) as a control. The aims of the work were to study the effect of drip irrigation circuits (DIC) and lateral lines lengths (LLL; where): (LLL1 = 40 m, LLL2 = 60 m, and LLL3 = 80 m) on pressure head (PH) and friction loss (FL). Regarding to LLL and according to PH values, DIC designs could be ranked in the following ascending order: TDIS \u3c CM1DIS \u3c CM2DIS. The differences in PH among DIC de-signs were significant at the 1% level. The de-pressive effects of LLL on PH could be ranked in the following ascending order: LLL1 \u3c LLL2 ≤ LLL3. Differences in PH among LLL treatments were significant at the 1% level except that be-tween LLL2 and LLL3. The effects of interactions among: DIC × LLL on PH were significant at the 1% level with some exceptions. The highest value of PH (9.5 m) and the lowest one (6.05 m) were achieved in the interactions of CM2DIS × LLL1 and TDIS × LLL3, respectively. The shapes of the energy gradient lines were affected by DIC and LLL treatments used through their effect on ΔH/H ratio. However, they followed similar trends. According to the FL values, DIC and LLL treatments could be ranked in the following descending orders TDIS \u3e CM1DIS \u3e CM2DIS and LLL1 \u3e LLL2 \u3e LLL3. The differences in FL among DIC and LLL were significant and the effects of interactions among DIC × LLL on FL were significant at the 1% level. The maximum and mi- nimum values of FL were obtained in the inter-actions: TDIS × LLL3 and CM2DIS × LLL1, respectively. Therefore, the CM2DIS system is recommended for use where technically feasible