ABSTRACT
SURFACE IRRIGATION EFFICIENCY IN CRACKING SOILS AS INFLUENCED BY WATER RESTRICTIONS
A. ZAIRI and A. SLATNI Institut National de Recherches en Genie Rural, Eaux et Forets - Tunis, Tunisie J.C. MAILHOL Cemagref - Division Irrigation - Groupment de Montpellier, France H. ACHOUR Ecole Sup6rieure des Ingenieurs de 1'Equipement Rural - Medjez El Bab, Tunisie
Abstract An experimental study has been carried out in order to improve surface irrigation practices in cracking soils of the Lower Medjerda Valley. The experiments deal with soil depletion impact on the irrigation efficiencies. A comparison between border and furrow practices was conducted on wheat usually irrigated by the border technique in Tunisia. The advance infiltration process was analysed using the calibration of the infiltration parameters on the advance trajectory (closed-end furrow and closed-end border practices). This calibration was conducted by means of two modelling approaches allowing hydraulic efficiencies to be estimated. The two main conclusions which can be derived from this study are: (1) water losses due to border practice under cracking soils can be significantly reduced by adopting the furrow practice without yield decreases; (2) according to the furrow practice, the irrigation strategies optimizing the efficiencies (hydraulic and agronomic) consist of giving two water applications to the crop. The first one insures crop emergence whereas the second has to be given when the soil water depletion reaches 90% of available water for the central region (low rainfall occurrence) and 30% for the northern region of Tunisia. The interest of coupling a water balance estimation with an operative furrow model in order to identify the best irrigation strategy on the whole irrigation campaign is here underlined. Keywords: surface irrigation, water restrictions, soil moisture deficiency, cracked soils, wheat production.
