WATER-USE AND SOIL-MOISTURE DEPLETION BY OLIVE TREES UNDER DIFFERENT IRRIGATION CONDITIONS

12 year old cv Kalamon olive trees irrigated at soil water potential r anges of -0.02 to -0.06 MPa (Psi 0.2) and -1 to -1.5 MPa (Psi 15) were compared with non-irrigated (NON-IRR) trees. Irrigation water was app lied by two drip laterals per row (DR) or a microtube-fed basin at eac h tree (BAS) for Psi 0.2 and one drip lateral per row (DR1) or a micro tube-fed basin at each tree for Psi 15. Soil moisture depletion in the non-wetted areas of the irrigated treatments was greater than that of the wetted ones, but about the same as the non-irrigated treatment. S oil moisture depletion in the non wetted areas of the irrigated and no n irrigated treatments occurred mainly during May-June. Soil moisture reached wilting percentage at the end of September in the non-wetted a reas of the Psi 0.2, at the end of August in the non-wetted areas of P si 15 and at the end of July in the non-irrigated treatment. Total soi l moisture reserve depletion was generally greater in the upper soil l avers of the wetted and non-wetted areas. The amount of irrigation wat er used was higher at the Psi 0.2 than at the Psi 15 treatment, but it was not noticeably different between the drip and basin irrigation me thods within the same soil water potential levels. Evapotranspiration of irrigated trees during May-September period was met mainly from irr igation water (75-90%), less from the reserves of the soil moisture (1 0-20%) and lesser still from the rainfall of the respective period (2. 5-5%). Crop coefficient, expressed as an evapotranspiration to class ' 'A'' pan evaporation ratio, increased from 0.4 to 0.65 for the Psi 0.2 , maintained at about 0.3 to 0.4 for the Psi 15 and decreased from 0.2 to 0.05 for the non irrigated treatment. Crop coefficients were not m arkedly different between drip and basin methods within the same soil water potential levels.