Comparative study on water availability for drip irrigation

In order to determine the best combination between duration and frequency o f drip irrigation for various inter-dripper spacing, we analysed the availa bility of water within the root zone of a tomato culture irrigated using la teral drippers each outputting 4 1 h(-1) discharge rate. Three spacings wer e studied, namely 30, 50 and 70 cm, Studying systematic irrigation duration of 4-1/2 hours, we observed at the end of each irrigation average volumetric water contents exceeding the fiel d capacity. Indeed, with the examination of the evolution of the water cont ents within the bulb, it is noticed that the water content at the field cap acity was reached after 25 minutes, 50 minutes and 2 hours respectively for 30, 50 and 70 cm spacing. But the humidification of the whole culture line was observed only after the respective times of 1, 2 and 4 hours (Ould Moh amed El-Hafedh et al., 2000). The irrigations were taken again with these reduced durations (1, 2 and 4 h ours for 30. 50 and 70 cm spacing respectively) in order to evaluate and co mpare water consumption of the culture under the various treatments. In case of systematic irrigation duration, the period separating two succes sive waterings was five, four and three days for 30, 50 and 70 cm spacing r espectively. For the reduced irrigation durations, it is imperative to irri gate after three days for the 50 and 70 cm spacings and after two days for the 30 cm. spacing. Comparing water consumption for the reduced durations and those of the syst ematic duration, we observed water savings of about 20, 15 and 5% respectiv ely for 30, 50 and 70 cm. spacing. The comparison between the reduced durat ions shows that the most significant water saving was obtained with the 50 cm spacing. Copyright (C) 2001 John Wiley & Sons, Ltd.