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J.W. Buxton and Wenwei Jia

The controlled water-table irrigation (CWT) system was evaluated for vegetable seed germination and transplant growth. The system is a modification of capillary mat irrigation except that the mat along one side extends over the edge of the bench into a narrow trough running along the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn by capillarity from the trough upward to the bench surface and then moves by capillarity to the opposite side of the bench. The system automatically maintains a constant air: water ratio in the growing media. Seeds of broccoli, tomato, and pepper were germinated in a 96-cell plug tray and grown to transplanting stage with the CWT system. A factorial experiment consisted of two growing media combined with CWT treatments of 2 and 4 cm. Excellent germination and high-quality seedlings were produced with all treatments. No differences were observed in growth of seedlings at 2 vs. 4 cm or between the two growing media. The CWT system is capable of maintaining a constant uniform water: air ratio in all plug cells on a commercial growing bench. Nutrient solution does not run off the bench. The CWT potentially is an excellent system for the irrigation of vegetable transplants.

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Jeff B. Million and T.H. Yeager

with either the nursery’s traditional irrigation practice or with CIRRIG. The irrigation system used at SWN was manually turned on and off by nursery staff. Once turned on, the system automatically cycled (typically one to three cycles per zone) through

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Jeff B. Million and Thomas H. Yeager

to large containers (≥7 gal) placed in lower densities and irrigated with directed microirrigation, typically using spray stakes. A second challenge is accounting for the variability in the irrigation system’s ability to deliver water uniformly within

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Edward W. Bush and Pamela B. Blanchard

. In early spring, students plant seeds of native plants. They maintain the seedlings over the spring semester. The teacher and school control the container yard and the seedlings during the summer to ensure that the irrigation system is working

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Marc W. Van Iersel, Sue Dove, Jong-Goo Kang, and Stephanie E. Burnett

containers and irrigates them based on container-specific θ thresholds. This irrigation system can maintain θ within a narrow range and automatically adjusts irrigation as plants get larger or environmental conditions change ( Nemali and van Iersel, 2006

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Xuewen Gong, Shunsheng Wang, Cundong Xu, Hao Zhang, and Jiankun Ge

irrigation system (the distance between emitters was 30 cm, and flow rate was 1.1 L·h −1 ). The irrigation amount and frequency were determined on the basis of the accumulated water evaporation of the D20 pan placed above the canopy. Irrigation events were

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Albert E. Smith and Will Corley

Lysimeters were developed in the greenhouse for simulating golf course greens with `Tifdwarf' bermudagrass and `Penncross' bentgrass overlying USGA specified rooting substratum. The lysimeters were constructed by subtending wooden flats containing turfgrass (38 × 38 × 14 cm deep) with polyvinyl chloride tubes (15 cm diam. × 52 cm deep) containing USGA-recommended rooting mixture for each turfgrass. The base of the tubes was capped with a closure containing an exit port for collecting the effluent drainage. An automatic irrigation system was developed by mounting flat fan nozzles on a cable driven roller 55 cm above the grass sod. The automatic water system is calibrated to irrigate at a rate of 0.1 cm min-1 for predetermined time-periods and volumes. The water flow through the lysimeters is uniform with a coefficient of variation less than 10% for 36 lysimeters. Data on chemical movement following treatment with three herbicides and weekly applications of fertilizer will be presented.

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J. Norrie, M.E.D. Graham, P.A. Dubé, and A. Gosselin

An automatic irrigation system was designed for use on green-house tomatoes growing in peat-based substrates. This system uses electronic tensiometers to monitor continuously substrate matric potential (SMP) in peat-bags. The system also uses the Penman equation to evaluate potential evapotranspiration (PET) through the acquisition of many greenhouse environmental parameters. Through a series of linear equations, estimates of PET are used in a computer-controller system to vary the electrical conductivity (EC) of irrigated nutrient solutions, as well as SMP setpoints at which irrigations are started. Such modifications to current irrigation management systems may improve fruit quality and reduce the risk of water stress during periods of high PET by irrigating more frequently with less-concentrated nutrient solutions. Conversely, during periods of low PET, irrigation is less frequent with more-concentrated nutrient solutions. Although no differences were found in fruit number or overall yield using variable nutrient solution EC, plant fresh weight was higher in those treatments. It is concluded that an integrated tensiometer-PET system may give increased precision to irrigation management and the control of crop growth in the greenhouse.

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Jack W. Buxton and Wenwei Jia

Cabbage seed was germinated and grown to transplanting size in a 98-cell tray using an automatic irrigation system based on the principle of maintaining a constant water table (CWT) relative to the growing medium in transplant trays. Seedlings obtained a nutrient solution from a capillary mat with one end suspended in a trough containing the solution. The distance between the nutrient solution surface and the transplant tray bottom was regulated with a water level controller. The nutrient solution was resupplied from a larger reservoir. A polyester material on top of the capillary mat allowed solution movement to the roots but prevented root penetration into the mat. The water table placement below the tray determined the water content in the growing medium. Seedling growth was evaluated using two growing media combined with two water table placements. Excellent quality seedlings were produced; the CWT irrigation system satisfactory provided water and nutrients for the duration of the crop. The only problems observed were dry cells, less than 2%, because of no media–mat contact and algae growth on the media surface using the higher water table. The CWT irrigation system is adaptable to existing greenhouse vegetable transplant production systems. It is automatic and can provide a constant optimum amount of moisture for seedling growing. It can be adjusted for phases of seedling growing such as more water during germination and can create water stress near transplanting time to either harden off or hold plants because of unfavorable planting conditions.

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Sloane M. Scheiber* and Richard C. Beeson Jr.

Petunia `Midnight' were grown in drainage lysimeters in an open-sided clear polyethylene covered shelter to evaluate growth responses in response to alternative irrigation strategies. Three irrigation methods were evaluated: tensiometer-controlled automatic irrigation system, regularly scheduled irrigation utilizing an automated controller, and human perception of plant irrigation need. Drainage lysimeters (250 L) were backfilled with native sand field soil to simulate landscape conditions and managed with Best Management Practices. Following establishment, lysimeters irrigated by an automated controller were irrigated 1.3 cm daily. Tensiometer-controlled lysimeters were irrigated when plant available water (2.5 kPa to 1.5 MPa) had declined to 70% or less, and were irrigated back to field capacity. Canopy growth indices and leaf gas exchange measurements were evaluated relative to irrigation strategies. Actual evapotranspiration was calculated for each replication. Daily irrigation resulted in significantly higher assimilation rates, transpiration rates, and final shoot dry weights than the other treatments tested. Assimilation rates and transpiration rates were significantly higher for tensiometer-controlled irrigation than the human judged treatment, but no differences were found in final shoot dry mass.