DRIP IRRIGATION SCHEDULING OF CITRUS ORCHARD IN TUNISIA

摘要

Drip irrigation scheduling of Clementine mandarin grove (planted since 1978) wasrncarried out at citrus orchard located at Cap Bon on the Mediterranean coast ofrnTunisia, with layered soil (sandy on sandy clay loam). The irrigation schedulingrnprogram was monitored using a simple method based on soil water status among thernprospected rooting zone (soil water balance and potential) coupled with crop waterrnrequirements determination, during three years, from 2005 to 2007.From the obtained results, the following conclusions would be drawn:1. Prospecting showed that Clementine root system was located by 65% in the toprnsoil surface layer and the remaining part is located in the subsequent layer with arnparticular root concentration (25%) within the layer’s transition zone. No rootsrnhave been observed growing deeper than 1.00 m.2. Soil moisture characterization is useful to identify the water retention and tornestablish the frequency of soil watering,rn3. Soil water potential associated to soil moisture measurement represents arnsuitable way to estimate water deficit and irrigation scheduling,rn4. Irrigation triggering should be conducted in two phases. During the “flowering-rnJune physiological fruit drop” period (February - June) the irrigation should berntriggered when the 0.25 m deep tensiometer reading reaches 10 × 10~(-3) MPa (0.1rnbar) while during the period of “fruit growth-ripening” (July-October) the tensionrnwould be 15 × 10~(-3) MPa (0.15 bar). These critical levels of soil water tensionsrncould be recommended in order to establish an irrigation scheduling of citrusrncultivated on low water retention sandy soilsrn5. The following three dimensional regression model could describe the seasonalrnsoil moisture distribution, within the root zone under drip irrigation: Z = 0.054 + 0.873 10~(-3) × - 0.23 10~(-5) x~2 - 0.00163 y + 0.258 10~(-4) y~2 - 0.83 10~(-6) x y(r~2=0.82~(**))The obtained results, has given in hand materials for the dissemination of the testedrnmethodological approach. When used properly, it can enhance the irrigator’s chancesrnof success.