University of California

Simplified tree water status measurements can aid almond irrigation


David A. Goldhamer
Elias Fereres

Authors Affiliations

D.A. Goldhamer is UC Cooperative Extension Water Management Specialist, Kearney Agricultural Center, Parlier; E. Fereres is Professor, Institute of Sustainable Agriculture-CSIC and University of Cordoba, Cordoba, Spain.

Publication Information

Hilgardia 55(3):32-37. DOI:10.3733/ca.v055n03p32. May 2001.

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Using tree water status measurements in orchard irrigation management is predicated on the fact that these values are closely linked to important physiological processes, such as growth. In our study, stem water potential (SWP) was highly correlated with vegetative growth in almond trees. However, the SWP technique requires that leaves be covered by small, foil-covered plastic bags for a certain time prior to the pressure chamber measurement and that the atmospheric vapor pressure deficit (VPD) in the orchard be considered in interpreting the data. This can be time consuming and labor intensive for growers. Growers need alternative approaches for taking pressure chamber measurements that are rapid, simple and easy to interpret. We found that measurements of shaded leaf water potential (LWP), taken when the leaf was covered by a damp cloth for the short time between leaf excision and placement in the pressure chamber, correlated well with SWP. Moreover, air temperature at the time of measurement was as useful as VPD for interpreting shaded LWP as an indicator in irrigation management. In addition to weather, this work identified operator differences as a major source of variation in water potential measurements. Plant-based measurements can be useful tools if precautions are taken concerning variability. Shaded LWP has logistical advantages over SWP and this study suggests that it can be used without sacrificing accuracy.

Further reading

Bradford KJ, Hsiao TC, Lange OL, Nobel PS, Osmond CB, Ziegler H. Physiological responses to moderate water stress. Physiological Ecology II: Encyclopedia of Plant Physiology (N.S. Vol 12B). 1982. New York: Springer-Verlag. p. 264-312.

Fereres E, Goldhamer DA, Stewart BA, Nielsen DR. Deciduous fruit and nut trees. Irrigation of Agricultural Crops.. 1990. Madison, WI: Amer Soc Agron, Monograph #30. p. 987-1017.

Hsiao TC, Stewart BA, Nielsen DR. Measurements of plant water status. Irrigation of Agricultural Crops. 1990. Madison, WI: Amer Soc Agron, Monograph #30. p. 243-279.

McCutchan H, Shackel KA. Stem-water potential as a sensitive indicator of water stress in prune trees (Prunus domestica L. cv. French). J Am Soc Hort Sci. 1992. 117(4):607-611.

Shackel KA, Ahmadi H, Biasi W, et al. Plant water status as an index of irrigation need in deciduous fruit trees. Hort Tech. 1997. 7(1):23-29.

Goldhamer D, Fereres E. 2001. Simplified tree water status measurements can aid almond irrigation. Hilgardia 55(3):32-37. DOI:10.3733/ca.v055n03p32
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