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Marc van Iersel and Ron Oetting

Ebb-and-flow systems can be used to apply systemic pesticides to greenhouse crops without worker exposure or runoff. However, there is little information on the efficacy of pesticides applied with ebb-and-flow systems. We are using silverleaf whitefly (Bemisia argentifolii) control on poinsettia (Euphorbia pulcherrima) with imidacloprid as a model system to study pesticide efficacy in ebb-and-flow systems. The objective of this study was to determine the effect of the amount of insecticide taken up by the pot on the efficacy of whitefly control. Different amounts of imidacloprid uptake were obtained by not watering the plants for 0, 1, 2, or 4 days before the imidacloprid application. The imidacloprid (132 g·L–1) was applied once when the roots of the cuttings had reached the side of the pots. These treatments were compared to an untreated control on ebb-and-flow and a standard drench application (100 mL) to hand-watered plants. Pots in the different subirrigation treatments absorbed 12 to 175 mL of imidacloprid solution. Four days after the application, leaf tissue of the hand-watered plants contained 8 to 20 times more imidacloprid than the subirrigated plants. Efficacy was determined from the percentage of surviving mature whiteflies after 2 days on the plants and by counting the number of immatures after 2 weeks. Surprisingly, imidacloprid efficacy was better in the subirrigated imidacloprid treatments than in the hand-watered treatment. Whitefly control in all subirrigated imidacloprid treatments was excellent, irrespective of the amount of imidacloprid solution taken up by the pots.

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Svoboda V. Pennisi, Marc W. van Iersel, and Stephanie E. Burnett

The growth of three english ivy cultivars in ebb-and-flow subirrigation systems was examined under three photosynthetic photon flux (PPF) treatments (low, medium, or high, corresponding to an average daily PPF of 3.2, 5.4, or 8.5 mol·m–2·d–1, respectively) and four fertilizer concentrations (0, 100, 200, or 300 mg·L–1 N) geared toward production of acclimatized foliage plants. Marketable quality english ivy can be subirrigated with 100 mg·L–1 N. Although 8.5 mol.m–2.d–1 produced the maximum shoot dry weight (SDW), good quality plants also were produced under 5.4 mol·m–2·d–1. `Gold Child', `Gold Dust', and `Gold Heart' english ivy produced with low fertility and low light may be better acclimatized and show superior performance in interior environments. Under light levels lower than 8.5 mol·m–2·d–1, `Gold Heart' had less variegation (12% or 21% for ivy grown under 3.2 or 5.4 mol·m–2·d–1, respectively). `Gold Dust' and `Gold Child' had 65% and 22% variegated leaf area, respectively, when grown under 5.4 mol·m–2·d–1 PPF. Under 5.4 mol·m–2·d–1 PPF, `Gold Dust' retains attractive foliage with overall perception of increased lighter-green coloration.

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Martin P.N. Gent, Wade H. Elmer, Kranti Macherla, and Richard J. McAvoy

; however, studies have shown over-watering by 10% to 30% is recommended to prevent salinity buildup in the root medium ( Mastalerz, 1977 ). By comparison, subirrigation, and in particular ebb and flow, systems use water more efficiently ( Dole et al., 1994

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John M. Dole, Janet C. Cole, and Sharon L. von Broembsen

`Gutbier V-14 Glory' poinsettias (Euphorbia pulcherrima Willd. Ex. Klotzsch) grown with ebb-and-flow irrigation used the least amount of water and produced the least runoff, and plants grown with capillary mats used the greatest amount of water and produced the most runoff, compared to microtube and hand-watering systems. The maximum amount of water retained by the pots and media was greatest for the microtube and ebb-and-flow systems and became progressively lower for the hand-watering and capillary mat systems. The media and leachate electrical conductivity from plants grown with subirrigation systems was higher than those grown with top irrigation. For the two top-irrigation systems (microtube and hand-watering), plants grown with 250 mg N/liter from a 20N-4.4P-16.6K water-soluble fertilizer had greater leaf, stem, and total dry weights than those grown with 175 mg N/liter. The two subirrigation systems (ebb-and-flow and capillary mat) produced plants that were taller and had greater leaf, stem, and total dry weights when grown with 175 than with 250 mg N/liter. The higher fertilizer concentration led to increased N, P, Fe, and Mn concentration in the foliage. Nitrogen concentration was higher in top-irrigated plants than in subirrigated plants. The ebb-and-flow system produced the greatest total dry weight per liter of water applied and per liter of runoff; capillary mat watering was the least efficient in regard to water applied and runoff.

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Marsha Ann Bower, David H. Trinklein, and John M. Brown

Recent trends in greenhouse container production suggest using ebb and flow irrigation for water conservation and pollution control. A major problem in this system is management of soil borne pathogens. Some species of Trichoderma, a beneficial fungi, are known to control Pythium and Phytopthora in container production. This study investigates the potential of applying a Trichoderma conidial spore suspension in an ebb and flow irrigation system. Trichoderma conidia were collected from culture and placed in 101 l stock solution tanks at 10-2 and 10-4 colony forming units (CFU) per ml. Six inch container grown Dendranthema grandiflora `Delano', were irrigated as needed. To determine Trichoderma density in the root environment, soil samples were acquired from the container at 7 day intervals. Results showed that initial population densities of 10-4 CFU/ml were required to achieve adequate container populations to control disease after one irrigation. This study successfully demonstrated that Trichoderma could be dispersed through irrigation water into container plants in an ebb and flow system.

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Theo J. Blom and Brian D. Piott

High-volume top irrigation (Chapin) was compared to subirrigation (ebb and flow) using 15-cm-diameter (1.56 liter) pot-grown chrysanthemums [Dendranthema ×grandiflorum (Ramat.) Kitamura] with peatwool (50 peatmoss: 50 granulated rockwool) as the growing substrate. Preplant moisture contents (25%, 125%, and 250%, gravimetric) and compaction (0, 20, and 50 g·cm-2) of the peatwool were also studied. Shrinkage of growing substrate was large (>309'6 of pot volume) when peatwool in the pots was not compacted. Compaction reduced shrinkage and produced plants with larger leaves, more fresh weight, and longer stems than without preplant compaction. Drainable pore space, container capacity, and total porosity was not affected by compaction. The higher preplant moisture contents increased drainable pore space but had no effect on plant growth. Chapin-irrigated plants had significantly more fresh weight (+ 24%) at the pea-size bud stage than plants grown in the ebb-and-flow system. The difference in growth was similar at flowering but significant only at P = 0.08. Soluble salts concentration in the peatwool and foliar nutrient contents differed at flowering for the two irrigation systems.

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David S. de Villiers and Robert W. Langhans

Protein is an important and essential dietary component. Common bean, a major source of vegetable protein in the Americas, was chosen for study in controlled environments with a view to its potential for use in space colonies. Eighteen 0.58-m2 stands of the cranberry type of bean, `Etna', were grown in the greenhouse at plant densities of 7, 15, and 28 plants/m2 in a recirculating ebb-and-flow system. Duration of photoperiod and thermoperiod was 16 h. Day/night temperatures settings were 25/20 °C. Daily light integral was matched across greenhouse sections by means of supplemental lighting; it averaged 17 mol/m2 per day. Crop cycle was 70 days from seed to harvest. At harvest, plants were dismembered so that dry weights of leaf, branch, stem, pod, and bean yields could be separately measured by node of origin. Internode lengths were recorded, and all loose trash recovered. The relationship between yield and plant density followed the form expected. Yield of edible biomass at 7 plants/m2 (284 g/m2) was 88% of that at 28 plants/m2 (324 g/m2), a significant difference. At 15 plants/m2 it was 97%. The trend suggests that further gains (but only very small) in yield can be expected with increased density in this cultivar. Productivity and quantum yield at 28 plants/m2 were 4.69 g/m2 per day and 0.27 g/mol, respectively. The coefficient of variation for plants grown at 28 plants/m2 was three times that of plants grown at 7 plants/m2 (0.88 vs. 0.26). Yield component analysis, harvest index, and plant morphology at the different planting densities are discussed.

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Puffy Soundy, Daniel J. Cantliffe, George J. Hochmuth, and Peter J. Stoffella

Several levels of P were supplied via floatation irrigation to `South Bay' lettuce (Lactuca sativa L.) transplants to determine the optimum P concentration necessary. Plants were propagated by floating flats (ebb and flow system) in a nutrient solution containing P at either 0, 15, 30, 45, or 60 mg·L-1 in summer and fall experiments, and either 0, 15, 30, 60, or 90 mg·L-1 P in a factorial combination with 60 or 100 mg·L-1 N in a winter experiment. Adding more than 15 mg·L-1 P had minimal effect on growth. Transplants produced with 0 P grew poorly, regardless of the level of N applied. Nitrogen at 100 mg·L-1 improved the response of shoot growth to any level of P, but adversely affected root growth compared with N applied at 60 mg·L-1. In general, relative growth rate was improved, while net assimilation rate was reduced at all levels of P. High-quality transplants had a root to shoot ratio of about 0.25, total root lengths between 276 and 306 cm, and total root area between 26 and 30 cm3 in a 10.9-cm3 cell volume. Only 30% of the plants produced without P could be pulled from the transplant flats, whereas 90% could be pulled when P was added. Pretransplant P hastened maturity and increased lettuce head weight at harvest in the field. This work suggested that at least 15 mg·L-1 P, supplied via floatation irrigation to a peat + vermiculite mix, was required to produce a transplant with sufficient roots for ease of pulling, rapid field establishment, and earlier harvest.

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Erin James and Marc van Iersel

Water conservation is increasingly important for growers in the United States, but there is little information on the use of alternative irrigation systems, such as ebb and flow, for the production of bedding plants. The objective of this study was to quantify the growth of Petunia ×hybrida Hort. Vilm.-Andr. `Blue Frost' and Begonia ×semperflorens-cultorum Hort. `Ambassador Scarlet' grown in an ebb and flow system in three soilless media and fertilized with P at 0, 50, or 100 mg·L-1 in the fertigation solution. After 5 weeks, plants grown with 50 or 100 mg·L-1 P had greater dry weight, height, and width than plants grown with 0 mg·L-1 P. Begonias grown with 50 or 100 mg·L-1 P had 38% more flowers than did those grown without P. Petunias flowered 4 to 7 days earlier when no P included in the fertilizer. Growing media had little effect on the plants. Begonias grown in Metro-Mix 220 had more inflorescences than those grown in Metro-Mix 366Coir. Changes in electrical conductivity (EC) and pH of all three media were similar over the course of the experiment. The EC dropped during the third and fourth week and rose again in the fifth week. The pH of the leachate from all three media dropped by an average of 1 unit during the experiment. The results indicate that petunias and begonias may be grown successfully with ebb and flow irrigation, using a variety of fertilizers and growing media. However, P must be included in the fertigation solution for optimal plant quality.

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Leqi Yang, Xiao Yang, Hong Zhao, Danfeng Huang, and Dongqin Tang

systems and is recognized as a high water productivity strategy. Ebb-and-flow system can adjust the water and fertilizer depending on the requirement of crop and reduce the overall water and nutrient use ( Ferrarezi et al., 2015b ). For instance, Holcomb