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Maria L. Burgos-Garay, Chuanxue Hong, and Gary W. Moorman

impact of bacterial isolates from recycled greenhouse irrigation water on three species of Pythium . Table 2. Average measurements (n = 40) of recycled irrigation water (RIW) samples collected from two commercial greenhouses in Pennsylvania and used in

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Daniel I. Leskovar and Ronald R. Heineman

Two studies were conducted to determine how greenhouse irrigation systems alter root elongation, root morphology, shoot growth, and water status of `TAM-Mild Jalapeño-1' pepper (Capsicum annuum L.) seedlings. Transplants were grown in containerized trays for 48 days in a greenhouse. Irrigation systems were 1) flotation (FI), 2) 28 days FI plus 14 days overhead (OI; FI + OI), 3) alternate OI and FI (OI–FI), and 4) OI. FI and OI–FI transplants maintained a uniform lateral root length increase between 20 and 41 days after seeding (DAS). In FI + OI and OI transplants, lateral root elongation tended to plateau at ≈31 DAS; however, by increasing the number and length (33%) of basal roots, OI transplants had a total root growth compensation during the remaining growth period. At 41 DAS, OI transplants had a higher shoot: root ratio (S: R = 5) and maintained a higher shoot water potential (Ψstem = –0.58) than FI transplants (S: R = 3; Ψstem= –0.69 MPa, respectively). In the second study, OI transplants maintained higher Ψstem than FI transplants. The latter had a lower stomatal conductance and photosynthesis rate than OI and FI + OI transplants. FI may be used to lower the S: R ratio and promote hardiness in jalapeño transplants.

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Steven E. Newman

Scaling from dissolved and suspended solids in irrigation water reduces the efficiency of greenhouse irrigation systems. Water deposits inside pipes reduce water flow and deposits may reduce the flow through irrigation emitters, often clogging them. If not properly maintained, the clogging of emitters requires constant maintenance. This results in considerable labor expense and/or emitter replacement. Scaling inside irrigation system pipes also has the potential to harbor plant pathogens from the resulting biofilms. Oxcide, a novel hypochlorous acid (HOCl) compound, is produced electrochemically by removing sodium and hydroxide from sodium hypochlorite. The elimination of sodium hydroxide from the product creates a nontoxic oxidizer. A system to inject Oxcide into irrigation water at a commercial Colorado greenhouse was installed to maintain irrigation efficiency of emitters and irrigation lines during Winter 2003. The oxidation reduction potential (ORP) was monitored and visual evaluations of irrigation equipment in the Oxcide treated zones compared to those zones not treated with Oxcide was conducted. During January through March, geranium stock plants were irrigated with water that maintained ORP levels at around 600 mV. Visual ratings of the irrigation emitters revealed that the injection of Oxcide in the irrigation water did reduce the level of deposition. Deposition on the main feed lines was so thick that they hindered the complete closure of existing valves. Treatment of the irrigation water Oxcide injection for six months successfully removed of the scale and deposits from the water line.

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Sadman Islam, Mark Lefsrud, Jan Adamowski, Blake Bissonnette, and Allison Busgang

campus. The Horticulture Services Building is used as a storage, processing, and retail space for the activities that occur in the surrounding gardens and the two greenhouses. Irrigation of the greenhouses consumes ≈700 gal of freshwater per day. The

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William R. Argo, John A. Biernbaum, and Darryl D. Warncke

Chemical analyses of 4306 randomly selected greenhouse water samples for 1995 from the United States and Canada were obtained from four analytical laboratories and graphically characterized using a distribution analysis. For pH, electro-conductivity (EC), and nutrient concentrations, a mean and median value and the percentage of samples with concentrations above or below those generally considered acceptable are presented for all samples and the 10 leading states in floricultural production. The median nutrient concentrations were more representative of the type of water found throughout the United States and Canada than that of the mean values because of the unequal distribution of the data. The overall median water source had a pH of 7.1; an EC of 0.4 dS·m−1; an alkalinity of CaCO3 at 130 mg·L−1; (in mg·L−1) 40 Ca, 11 Mg, 8 SO4−S, 13 Na, 14 Cl, 0.02 B, and <0.01 F; a Ca: Mg ratio of 3.2, and a sodium adsorption ratio (SAR) of 0.7. The information presented characterizes irrigation water and may assist in developing more refined fertilizer recommendations for greenhouse crop production.

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Stephanie E. Burnett and Marc W. van Iersel

fertilizer solutions determine the pH of soilless mixes Proc. Southern Nurs. Assn. Res. Conf. 48 538 541 van Iersel, M.W. Kang, J.G. Burnett, S. 2007 Making greenhouse irrigation more efficient: Effects of

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Steven E. Woerner and Douglas A. Hopper

A computer simulation model was developed to be used in evaluating irrigation scheduling techniques and assisting irrigation scheduling decisions under greenhouse conditions in Colorado. The model simulates variable greenhouse conditions and shows how each of four irrigation scheduling techniques responds to these conditions. Reports from the model detail numbers of irrigation events, sensitivities to parameters, and forecasts water usage. The model was also used to determine appropriate accumulation triggers for Colorado conditions.

Four techniques evaluated here include: time clock control; accumulated radiation; accumulated vapor pressure deficit; combination method (radiation and vapor pressure deficit). The model has shown the combination method to be the most sensitive to changes in environmental conditions, while the time clock method proved to be least sensitive (and most wasteful of water).

The model may evaluate additional irrigation scheduling techniques by including additional parameters in the model, and may readily be adapted to different climatic regions.

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Shiv K. Reddy and Michael A. Madore

Alkalinity of irrigation water affects pH of the plant growing media. High alkalinity water raises media pH and affects nutrient availability to plants and, thus, plant growth. Alkalinity levels in irrigation water vary in different regions. Knowledge of alkalinity levels would help growers and advisors in modifying cultural practices to suit the levels. To find out how the levels vary in different states, we searched our database of thousands of water analyses from across the country. Overall, 38% of the waters had <100 ppm CaCO3, a level not considered to be a concern for even small pots. About 74% of the waters had <200 ppm CaCO3, a level considered to be safe for large pots. The majority of the waters in the states along the eastern seaboard had <150 ppm CaCO3. In waters in the interior states, alkalinity levels varied. Pacific Northwest had most waters <150 ppm CaCO3. Detailed results—bar charts showing percent of waters at different alkalinity levels in each state and in the country will be shown.

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

data sets are independent ( Wallach, 2006 ). Until such studies have been conducted, simple descriptive models like this should not be used to automate greenhouse irrigation. Fig. 3. Daily light integral (top) and daily irrigation volume (bottom

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Peter Alem, Paul A. Thomas, and Marc W. van Iersel

al., 2005 ; Broschat, 1996 ; Merhaut et al., 2006 ). Timers are commonly used to control greenhouse irrigation and provide water according to a predetermined schedule. This may result in unnecessary water applications and leaching because a set