Tree heights and calipers were not different at each date ( Fig. 1) when cyclic irrigation was automatically applied three times daily, or cycles of irrigation were applied when container moisture tension exceeded 5 kPa as determined with tensiometers. The growth reduction was due to pruning.

Live Oak Growth with TensiometerLive Oak Growth with Tensiometer--controlled Cyclic Irrigationcontrolled Cyclic IrrigationLaura Miller Laura Miller

Texas AgriLife Extension, Tarrant County, Fort Wort h, TX 76102Texas AgriLife Extension, Tarrant County, Fort Wort h, TX 76102

Tom Yeager and Claudia LarsenTom Yeager and Claudia LarsenDept. Environmental Horticulture, Univ. of Florida, IFAS, Gainesville, FL 32611Dept. Environmental Horticulture, Univ. of Florida, IFAS, Gainesville, FL 32611

Abstract

Efficient use of water resources in plant production is important for sustainability. Irrigation water is often thought of as a low cost input, but over-application wastes this valuable resource. Cyclic irrigation has been shown to result in 50% less irrigation water applied without sacrificing live oak growth (Beeson and Haydu, 1995). The use of soil moisture sensors to prevent irrigation when substrate water content is above a critical level further reduced irrigation volume applied, while still providing sufficient water for plant growth. Tensiometers integrated with an irrigation controller limited cyclic irrigation applications to when moisture tensions were > 5kPa (5 centibars) and resulted in a 62 % reduction in the volume of water applied compared to a fixed daily three cycle irrigation schedule. Because tree growth was not negatively affected, these results indicate that the Best Management Practice of scheduling irrigation based on substrate moisture is an effective way for container tree producers to

Results

Live Oak Calipers

Live Oak Heights

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7/24/2006 10/13/2006 12/18/2006 3/21/2007 8/15/2007 11/2/2007 2/25/2008

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Tensiometer Cyclic Daily

Live oak trees ( Quercus virginiana ‘Cathedral’ #3 container) were planted May 2006 with a commercially prepared 6 pine bark: 4 Florida peat: 1 sand substrate (by volume) in containers called “The Smart Pot.” [24 inches diame ter and ≈14 inches high (High Caliper, Inc., Oklahoma City, OK].

The substrate was amended with dolomitic limestone and Florikan® Blend 15-4-9 controlled-release fertilize r (Florikan, Sarasota, FL) was applied during potting by distributing 1 lb of fertilizer around the roots of the transplant as the container was filled and all tree s were subsequently fertilized the same. Trees were place d 5 ft apart in a guy-wire supported row at Sun City Tree Farm, Ruskin, FL.

Irrigation was applied via one Chapin spray stake t ype P per container [(0.6 qt/min ≈12 psi) Chapin Watermatics, Inc.,Watertown, NY]. A water meter was installed in the main irrigation supply line for each of four irriga tion zones.

Switching tensiometers (Irrometer Model “LT”, Irrom eter Company, Inc., Riverside, CA) were used to activate irrigation cycles when the substrate moisture tensi on was greater (drier) than 5 kPa (5 centibars) during any of three scheduled activation times each day (mid-morning, m id-afternoon, and late afternoon) or three irrigation cycles were automatically activated daily by preset contro ller for a total of ≈ 2 gal/tree at beginning of study and 3.4 gal/tree at end.

Tree heights, calipers, and meter readings were det ermined July 24 (Aug. 3 for caliper), Oct. 13, and Dec. 18, 2006; Mar 21, Aug. 15, and Nov. 2, 2007; and Feb. 25, 2008.

AcknowledgementsThe authors acknowledge the cooperation of

Sun City Tree Farm, Ruskin, FL and support of the Florida Agricultural Experiment Station, FNGLA Endowed Research Fund, and the

Tampa Bay Wholesale Growers LAA.

effective way for container tree producers to conserve water.

Methods

Fig. 2 . Irrigation water applied from July 2006 to Feb. 200 8.

Fig. 1 . Live oak heights and calipers ± standard deviation.

The integration of tensiometers into irrigation control resulted in 62% less water applied compared to a fixed schedule of cyclic irrigation events ( Fig. 2). Even though less irrigation water was applied, tensiometers required monitoring and maintenance to ensure proper operation.

Live Oak Calipers

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Water Applied to Live Oaks

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Irrig

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