Vazão e uniformidade de distribuição de tubo gotejador em superfície e subsuperfície

The evaluation of irrigation system in subsurface allows to know the conditions of its performance in order to avoid environmental impacts and, also, economic losses in the localized irrigation. The objective was to evaluate the uniformity of distribution and flow rate of the dripping tube under surface and subsurface irrigation conditions. An experimental design was used in subdivided plots in the 5 x 5 factorial scheme, and four replications. The treatments consisted of 5 submersion depths of the dripper tube (0, 0.1, 0.2, 0.3 and 0.4 m) combined with 5 water inlet pressures in the dripper tube (49, 98, 147, 196 and 245 kPa). According to Merriam and Keller (1978) and Mantovani (2002), the lowest coefficient of uniformity of distribution was 95.55%, and the lowest coefficient of uniformity of Christiansen, 96.37%. The coefficient of variation of manufacturing was compliant with regulation ABNT NBR ISO 9261, being less than 7%. The characteristic equations developed in this work presented coefficient of determination of 0.99 and can therefore be used to calculate the actual flow.