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Avoidance of Drought Injury and Minimum Irrigation in a Mediterranean Climate: The Requirement for Acclimatized (Hardened) Plants

Roy M. Sachs and David A. Shaw
Arboriculture & Urban Forestry (AUF) March 1993, 19 (2) 99-105; DOI: https://doi.org/10.48044/jauf.1993.017

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Figures

  • Fig. 2.
    Fig. 2.

    Growth of shrubs at San Jose as a function of irrigation amounts from the end of March through September 1974. The 12.1 in were applied in three irrigations in May, July and September; the 29.6 in were applied in eight irrigations at 2-week intervals beginning in April. Rainfall for July 1973 through June 74 was 15.2 inches.

  • Fig. 3.
    Fig. 3.

    Fig. 3. Negative print of aerial infrared photo of San Jose plantings taken in May, 1976, the 5th year following irrigation treatments. From top to bottom the species are: Pinus radiata, Juniperis chinensis, Xylosma congestum, Nerium oleander, Cotoneaster parneyi, and ice plant. The 3 blocks from left to right are the irrigation treatments: 0,12.1, and 29.6 inches of water applied annually in the April to November.

  • Fig. 1.
    Fig. 1.

    Growth of shrubs at Irvine as a function of irrigation water received from March through September 1974. No bar appears for “0 inches irrigation” because no growth occurred under this condition. Each irrigation delivered 3.7 inches. Rainfall during the winter of 1973-74 was 10.9 inches. All but the nonirrigated plants retained an acceptable appearance for landscape purposes.

  • Fig. 4.
    Fig. 4.

    Growth of shrubs at Irvine, 1991, as a function of irrigation regime and growth retardant application. Flur equal to flurprimidol, Clippings were weighed in October 1991,11 months after pruning. Irrigation was automatic. A tensiometer with a magnetic switch set at −20 centibars controlled the irrigation valves. The controlling tensiometer was placed in the ligustrum block under an emitter at a two feet depth. Irrigation equal to ETo was delivered with the tensiometer set at − 20 cbars. For each irrigation cycle, the 0.25 ETo shrubs were irrigated for a period one quarter as long as the ETo block. Precipitation for September 1990 through October 1991 was 14.07 inches, with 5.86 inches falling in March 1991.

  • Fig. 5.
    Fig. 5.

    Leaf-air temperature differentials for San Jose Xylosma and ice plant as a function of irrigation regime. Temperatures were measured July 26, 1974, using infrared imaging system. Air temp. =76°F.

  • Fig. 6.
    Fig. 6.

    Soil moisture as a function of depth and irrigation regime at Irvine. Cotoneaster plants extracted water from at least a 3-ft depth in the nonirrigated block (these shrubs suffered leaf damage). Measurements were taken in October, 1974; rainfall from July 1973 through June 1974 was 10.9 inches.

  • Fig. 7.
    Fig. 7.

    Soil moisture as a function of depth and irrigation regime at San Jose. Soil samples were taken from below Xylosma plantings, at 12,22 and 36 inches, on September 16,1974.

  • Fig. 8.
    Fig. 8.

    Comparison of water lost from trees and pan evaporation (PAN)on Aug.22, 1991 in New York. SOPH ≡ Sophora japonica, FRAX = Fraxinus americana, AMELANCH = Amelanchier, TIL = Tilia americana (from Lindsey (21).

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Avoidance of Drought Injury and Minimum Irrigation in a Mediterranean Climate: The Requirement for Acclimatized (Hardened) Plants
Roy M. Sachs, David A. Shaw
Arboriculture & Urban Forestry (AUF) Mar 1993, 19 (2) 99-105; DOI: 10.48044/jauf.1993.017
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