Spatial variability of discharge and pressure in subunit of microsprinkler irrigation with used and new emitters

Abstract

This work studied in field the spatial distribution of discharge and pressure in subunit irrigated by microsprinkler, considering used and new emitters. The data were collected in 28 emission points spaced in 10 x 18 m. The mean values were submitted to normality test and also to a geostatistical analysis; the verification of the spatial dependence and of the interpolation was accomplished by the method of krigagem and the spatial continuities were studied by means of semivariograms for the discharges and pressures of the subunit with new and used microsprinklers. It is verified that the models varied if the emitter was new or used. The mathematical model that better adjusted to the discharge of the new and used emitters was, respectively, exponential and spherical; for the pressure, the model was the inverse of the discharge, that is, spherical for new emitters and exponential for used ones. The values for the used emitters of the nugget effect (Co), landing (Co+Cl) and reach (Ao) were of l.0 L h-1, 33 L h-1 and 218 m and of 0.43, 137 kPa and 58 m, for discharge and pressure, respectively. The coefficient of irrigation uniformity, the coefficient of uniformity of the system and the water application efficiency increased, respectively, in 11.9, 10.58 and 10.75%, when the used emitters were substituted by new ones. The maximum distance (reach) where the estimated data of discharge and pressure are spatially correlated extrapolated the length of the derivation line for the discharge with new and used microsprinklers and for the pressure only with new microsprinklers. The nugget effect for the pressure in the system was smaller when it was changed the used microasprinklers by new ones, the inverse was observed for the discharge. There was an increase in pressure as well as in discharge when the used microsprinklers were changed by new ones.