Hydraulic characterization of low flow drip irrigation emitters used in intensive horticultural crops in Almeria (Spain)

In the present work, a selection of drip irrigation emitters used in greenhouse horticultural crops in the province of Almeria, Spain, were hydraulically evaluated, studying their hydraulic behavior and whether they meet with quality standards. Since manufacturers are offering lower flow emitters less spaced, all drippers tested are low flow. The hydraulic characterization will indicate the discharge and emission uniformity of the manufactured emitters, which are the fundamental parameters for the study of water use efficiency in drip irrigation. In the province of Almeria, water is a limiting factor due to the existence of a semi-arid climate, and, in addition, these limited water resources are used by intensive agriculture which causes a high consumption of these resources.

In total, 21 emitters have been evaluated, including all possible drippers according to their type of insertion (inline, pinched or online and interlinea), hydraulic behaviour (non-compensating and self-compensating) and, within the compensating ones, (anti-draining and non anti-draining). Its flow rates are between 1 and 2.4 l/h, except for a non-compensating interlina emitter of 3.8 l/h.

To carry out these tests, the criteria of the ISO 9261:2004 standard have been followed, calculating the coefficient of manufacturing variation and the emitter discharge equation on a test bench located in the La Mojonera Centre (Almeria) of the IFAPA (Andalusian Institute of Agricultural and Fishing Research and Training).

The results of this study show very good behavior in most of the emitters, and, as a consequence, a low coefficient of manufacturing variation has been obtained. The discharge equation obtained in the laboratory shows a low emisión exponent in the self-compensating emitters, being, therefore, the compensation of the pressures very high in all cases. No statistically significant differences have been found between self-compensating and non-compensating emitters by analysing their manufacturing variation coefficients. Nor have any significant differences been found between self-compensating emitters according to whether they are anti-draining or non-anti-draining, considering also the coefficient of variation. In anti-draining emitters, all closing pressures are not satisfied according to the standard, and are exceeded with very high values. The opening pressure is met for two of the four emitters, and one of those that does not meet it does so with a very large value.