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Martin P.N. Gent and Richard J. McAvoy

, 1977 ). The runoff of water, fertilizer, and pesticides resulting from these irrigation methods is a potential risk to the quality of the environment in proximity to a greenhouse operation. Subirrigation, and in particular ebb and flow, systems are more

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Manuel Chavarria, Benjamin Wherley, James Thomas, Ambika Chandra and Paul Raymer

. Replicate studies consisting of four salinity levels of 2.5 (control), 15, 30, and 45 dS·m –1 EC were supplied via subirrigation into 1-m × 1-m × 5-cm-deep ebb and flow benches, similar to the method published by Raymer et al. (2005) . The control

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N.S. Khoury, E.J. Holcomb, J.W. White and M. Rand

Excessive electroconductivity measurements have been observed in the surface layer of subirrigated substrates. A hydrophilic gel and rockwool were used as pot mulches in order to reduce the surface layer salt buildup by absorbing the salts and/or reducing evaporation.

Six treatments of `Crimson Fire' and `Victoria' CVI geraniums were grown in 11 cm. pots. Treatments were: Trt 1 - top irrigation, N source 20-10-20; trt 2 - subirrigation, N source 20-10-20; trt 3 - subirrigation, N source in equal portions of 20-10-20 and CRF, gel mulch; trt 4 - subirrigation, N source CRF, gel mulch; trt 5 - subirrigation, N source in equal portions of 20-10-20 and CRF, wool mulch; trt 6 - subirrigation, all N source CRF, wool mulch.

Pots were divided into 3 equal volume portions. Electroconductivity, as a measure of soluble salt (SS) level, was taken. All treatments had increasing SS levels with increasing pot height. Trt 2 had surface layer salt levels significantly higher than trt 1. `Victoria' trts 3,4,5 and 6 surface layers had significantly lower SS levels than trt 1 surface layers. `Crimson Fire' trt 4's surface layer had significantly lower SS levels than the surface layer of trt 1. Trts 4 and 6 bottom layers of both cultivars had significantly lower SS levels than all other treatments.

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Mingying Xiang, Justin Q. Moss, Dennis L. Martin and Yanqi Wu

acclimation period, daily subirrigation was applied to all the pots by solution tanks (50 gal) that were fitted with a water pump and timer. The greenhouse nonpotable water source used in this study had a pH of 7.8, an electrical conductivity (EC) level of 0

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Patricia R. Knight, D. Joseph Eakes, Charles H. Gilliam and Harry G. Ponder

Seed geraniums (Pelargonium × hortorum Bailey `Scarlet Elite') were grown in 10-cm pots in a 1 pine bark : 3 peat moss : 1 perlite medium from 18 March until 5 May 1993. Plants received Osmocote 14N-6.1P-12.5K and either conventional overhead (CO), drip (DI), or subirrigation (SI). Subirrigation produced greater shoot and root dry weights than CO or DI. Plants grown using DI produced fewer branches than plants grown using CO or SI. Plants receiving SI reached anthesis before plants receiving CO or DI. Method of irrigation had no influence on total root, soil, or leachate N, but SI did increase total shoot N.

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Mingying Xiang, Justin Q. Moss, Dennis L. Martin, Kemin Su, Bruce L. Dunn and Yanqi Wu

capacity with a nutrient solution containing 2.6 g·L −1 N 13-2-13 + 6Ca + 3Mg of a plug special fertilizer solution. The grasses under prior salinity stress were flushed overhead daily with a 300 mL solution for 7 d before switching to subirrigation for 8

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Charles E. Barrett, Lincoln Zotarelli, Lucas G. Paranhos, Brian S. Taylor, Peter Dittmar, Clyde W. Fraisse and John VanSickle

in air temperature and potential nutrient losses from heavy rainfall events. Seepage irrigation (subirrigation) with broadcast fertilizer application dominates the cabbage industry in Florida, adding to the potential for nutrient loss. Seepage has low

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Albert T.Y. Mak and D.M. Yeh

Effects of nitrogen application on growth, stomatal conductance, transpiration, and chlorophyll content were studied in Spathiphyllum Schott 'Sensation' grown in sphagnum peat (SP)- and coir dust (CD)-based media with top-irrigation or subirrigation. Maximum shoot dry weight occurred at 8 mM N in plants grown in SP-based medium under top-irrigation and subirrigation, and in CD-based medium under subirrigation. For plants in CD-based medium under top-irrigation, maximum shoot dry weight was obtained at 16 mm N. In SP- or CD-based medium, shoot dry weight was greater at 4 and 8 mm N under subirrigation than under top-irrigation. Stomatal conductance and transpiration were reduced by nitrogen deficiency (0 N), greatly enhanced by 4 mm N, and decreased gradually at higher N levels. Chlorophyll content increased with increasing N concentration up to 8 mm. The percentage of maximum total dry weight increased quadratically as leaf N content increased from 1.5% to 3.5%. Nitrogen at 16 and 32 mm increased the number of leaves with marginal necrosis. Reduced growth and more leaves with marginal necrosis occurred in SP- or CD-based media with EC > 1.25 dS·m-1 in the middle and bottom layers.

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Thomas B. Bruning, Michael H. Chaplin and Henry G. Taber

Ground water contamination resulting from continuous liquid fertilization technologies is a serious problem facing greenhouse growers in the United States. Rooted Dendranthema grandiflora Tzvelev. cultivar 'Iridon' cuttings were transplanted into 11 cm pots filled with a 50% peatmoss and 50% perlite (v/v) media containing 0.10, 0.21, 0.42, or 0.84 g N from a controlled release 12-10-17 plus minors fertilizer deposited directly below the transplanted cutting. Pots were assigned to a top-water or subirrigation treatment.

Subirrigation reduced the nitrate leachate concentration by as much as 250 ppm as compared with top-watering. Fertilizer N rate linearly decreased plant height in both of the irrigation treatments. Final dry weight of the shoot peaked at the 0.21 g N rate in both the irrigation treatments.

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Berl M. Thomas

The containerized transplant commercial industry started in the United States in the 1960's. Since then, several different types of growing containers have been developed for the vegetable, tobacco, ornamental and forestry seedling industries. Two basic irrigation methods have developed including overhead and sub-irrigation systems. The irrigation system used depends on the crop needs, value, availability of water, and the need to reduce pesticide use and risk of disease. Sub-irrigation systems have reduced the spread of seed-borne and naturally occurring diseases. Overhead irrigation systems were predominantly used during the early years, but at present, both systems are used and selected for their respective advantages. Future developments in the transplant industry include reduction of production risks and to improve cost per production unit by reducing both nursery and farm labor requirements.