Determination of the water requirements in olive trees with lysimeters

Doctoral thesis abstract

Abstract

A compensation lysimeter with constant freatic water table of 2 x 2 x 0.80 m was installed in 2004 in a peach grove, in order to study the crop water consumption of the south of Uruguay. Measurements were taken in the first three growing seasons. Evapotranspiration the first season reached 5 mm d-1, equivalent to 56 L in the whole area. The second season, it went up to 5.6 mm d-1 (63 L). When the tree got its adult size, the maximum consumption remained around 6.3 mm d-1 (71 L). The crop coefficient (Kc) was around 0.9 the first season, and 1.2 the following two seasons. Basal crop coefficient (Kcb) was calculated and its value was adjusted by the tri-segmented model. The value was 0.78 the first season, 0.91 the second one, and 1.1 the third one. Some methodological observations are made regarding the lysimeter use. We suggested to add the soil water changes to the mass balance equation, as well as to incorporate irrigation from the surface. Another objective was to make local estimations of the pan coefficients (Kp) for the south of Uruguay to calculate the reference crop evapotranspiration according to Penman-Monteith modified by FAO (FAO-PM ETo). The use of a single Kp (0.71) during the irrigation season gave a good estimate for the south of the country. The use of this single coefficient to correct the pan evaporation data is simple, it is easy to deal with by producers, and it represents a good estimate of the ETo. This value must be calibrated for other areas of the country.