ABSTRACT


Edmundo Acevedo H.1, Norberto Fritsch F.2 y Kyoto Uriu3
 
The scope of this work was to establish the leaf water potential value at which a peach orchard should be irrigated. A nine years old Incomparable peach orchard was selected in the province of Santiago. The plants grawing in a deep alluvial soil (1.2 m), were irrigated by contour basins whenever tensiometers located at 60 cm depth reached 70 cb.
Leaf water potencial was measured by Scholander's method (pressure bomb) eveny three to four days. The measurements were made between 7:45 and 8:15 A. M. in fully mature leaves of the middle of the shoot. Care was taken to select leaves not directly exposed to sunlight. Measurements were also made between 2:30 and 3:00 P. M., considering that at this time of the day the evapotranspiration demand would be at a maximum.
The data obtained show that leaf water potential in peache leaves is a good index for changes in available moisture within the tensiometer range. Changes in soil water potential (matric) from -10 to -70 cb induced a decrease in leaf water potential from -95 to -165 p.s.i. (-665 to -1.138 cb) measured between 7:45 and 8:15 A.M. Values obtained between 2:30 and 3:00 P. M. did not show a clear trend, probably due to daily microclimatic variations. It is recommended to irrigate peach orchards when leaf water potential, measured early in the morning (7:30 - 8:30 A. M.) with the pressure bomb, reaches values around -165 p.s.i. The method could be highly useful to establish irrigation frequency, specially in those orchards growing in shallow alluvial soils (30 - 60 cm) where the quantification of soil water content and/or soil water energy status is extremely difficult.
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1Ing. Agr., M. S., Profesor de Relaciones Suelo-Agua-Planta. Facultad de Agronomía, Universidad de Chile. Casilla 1004, Santiago, Chile.
2Ing. Agr., M. S., Profesor de Riego. Facultad Agronomía, Universidad de Chile. Casilla 1004. Santiago, Chile.
3Pomologist, Ph. D., Profesor de Pomología. Dpt. of Pomology, University of California Davis, U.S.A.