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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.

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C. D. Stanley and G. A. Clark

The use of the recently developed fully-enclosed seepage subirrigation system for fresh market tomato production has demonstrated an improved ability to maintain a water table at a desired level (when compared to conventional ditch-conveyed seepage subirrigation) by means of more precisely controlled application and a greater uniformity throughout the field. This is achieved through use of microirrigation tubing rather than open ditches to convey water to raise the water table to desired levels. When manually controlled, the system has shown to save 30-40% in irrigation amounts primarily due to almost total elimination of surface runoff. An automated control system was designed and evaluated with respect to practicality, durability, and performance of various designs of level-sensing switches. The advantages and limitations of the designs in relation to water table control for tomato production will be presented.

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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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Jaime K. Morvant, John M. Dole, and Janet C. Cole

Euphorbia pulcherrima `Gutbier V-14 Glory' were grown with 220 mg·liter–1 N (20N–4.4P–16.6K) using ebb-and-flow (EF), capillary mat (CAP), microtube (MIC), and hand-watering (HAN) and were irrigated either daily (pulse - P) or as needed (regular - R). For all irrigation systems, pulse irrigation produced the greatest total dry weight. HAN-R produced lower total dry weight than all other irrigation systems and frequencies. Root dry weight was highest with pulse subirrigation (EF and CAP). MIC-P, EF-P, and EF-R were the most water-efficient treatments. The experiment was repeated twice with similar results. In a second experiment, Pelargonium ×hortorum `Pinto Red' root balls were sliced into three equal segments; top, middle, and bottom. For all irrigation systems, root counts were lowest in the top region. EF root counts were greatest in the middle region, while MIC root counts were greatest in the bottom region. The two subirrigation systems had higher average root counts than the two top-irrigated systems (HAN and MIC). In general, there was less difference in EC between regions for top-irrigated than for subirrigated root balls. The EC was lowest in the bottom and middle regions of EF and the bottom region of MIC and CAP. For subirrigation, the highest EC was in the top region. For all systems, pH was lowest in the bottom region.

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Troy M. Buechel, David J. Beattie, and E. Jay Holcomb

A characteristic problem with peat moss is its difficulty in initial wetting and rewetting, especially in a subirrigation system. Wetting agents improve wetting characteristics primarily by reducing the surface tension of water. This results in a rapid, uniform movement of water by capillary rise through the growing medium.

Two methods were used to compare the effectiveness of different wetting agents: gravimetric and electrical. Ten cm pots containing peat moss were placed in a subirrigation system. The gravimetric method used a laboratory scale where pots were periodically weighed to determine the amount of water absorbed. The electrical method utilized thin beam load cells, which have strain gages bound to the surface, to determine the weight of a suspended object. Load cells were coupled with a Campbell Scientific datalogger to collect data every minute without removing the pot from subirrigation. Because the effect of buoyancy altered the true weights, equations were generated to adjust the water uptake values. Corrected weights were used to create absorption curves for comparison of the slopes to determine which wetting agent has the fastest rate of absorption. The load cell reliably and accurately described the wetting characteristics of Peat moss and we found good agreement with the gravimetric method.

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John Kabashima

Several production nurseries were surveyed about techniques used to reduce water usage and runoff. The nurseries surveyed used from 400,000 gallons of water per day to 5,000,000 gallons of water per day during peak usage. Water availability and the potential for nitrate runoff from large production nurseries to contaminate the environment have resulted in requirements by regulatory agencies to decrease water usage and runoff. Nurseries have complied by using techniques such as drip irrigation, subirrigation, pulsing, recycling, and computer controlled irrigation systems. The use of techniques such as recycling and “better management practices” have resulted in significant decreases (approximately 30%) in water usage.

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M.S. Albahou and J.L. Green

Incidence of blossom-end rot (BER) of tomato is known to increase with increasing salinity in hydroponics and field tomato crops due to osmotic stress and imbalanced ionic ratio in the media solution. The present investigation evaluated salinity effects on the occurrence of BER of tomato in a completely closed root environment known as the closed insulated pallet system (CIPS). The CIPS is a continuous sub-irrigation capillary system with water moving from reservoir to rootzone in response to plant uptake and loss through transpiration and growth. In CIPS, fertilizer reserve is placed at the top surface of the root matrix, so fertilizer ions move downward by diffusion. Various tomato genotypes were seeded directly into CIPS in Spring. The experiment was terminated at a 100-day growing period. The incidence of BER was calculated as percent affected fruits. Salinity treatments consisted of five concentrations ranging from 0 to 10 g/L NaCl. One salinity treatment was 1 g/L CaCl2. In CIPS, the salt gradient created by uptake of saline water had lowest concentration at the top of root compartment where fertilizer was placed. Therefore, there was minimal ionic interactions between fertilizer ions and ions from the saline water. The uptake of water and plant growth decreased with increasing salinity concentration. The addition of Ca in the sub-irrigation water had no effect on the occurrence of BER. The incidence of BER correlated negatively with salinity level and plant growth in the CIPS.

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Jaime K. Morvant, John M. Dole, and Earl Allen

Pelargonium hortorum Bailey `Pinto Red' plants were grown with 220 mg·L−1 N (20N-4.4P-16.6K) using hand (HD), microtube (MT), ebb-and-flow (EF), and capillary mat (CM) irrigation systems. At harvest, root balls were sliced into three equal regions: top, middle, and bottom. A negative correlation existed between root medium electrical conductivity (EC) and N concentration to root number such that the best root growth was obtained with low medium EC and N concentrations. EF root numbers were greatest in the middle region. The two subirrigation systems (EF and CM) had higher average root numbers than the two surface-irrigation systems (HD and MT). For all irrigation systems, root numbers were lowest in the top region. In general, less difference in medium soluble salt and N concentrations existed between regions for surface-irrigated than for subirrigated root balls. Soluble salt concentration was lowest in the bottom and middle regions of EF and the bottom region of MT and CM. For subirrigation, the highest medium soluble salt and N concentration was in the top region. For all systems, pH was lowest in the bottom region. Plant growth for all irrigation systems was similar. EF and MT systems required the least water and EF resulted in the least runoff volume.

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William R. Argo and John A. Biernbaum

Hybrid impatiens were grown in 15 cm pots containing one of six root medium. After seven weeks, plant available water holding capacity (AWHC) was measured as the difference between the drained weight of the plant and pot after a one hour saturation and the weight of the pot when the plant wilted. Water absorption potential (WAP) was calculated as the capacity of each root medium to absorb applied irrigation water up to the AWHC and was measured at two moisture levels with top watering (two leaching fractions), drip irrigation (two leaching fractions) and flood subirrigation. Top watering moist media (initial AWHC = 35%) with leaching fractions of 30+ % was me most efficient method of rewetting media and was the only irrigation method tested to obtain WAP's of 100%. In comparison, flood subirrigation was the least efficient method of rewetting media with WAP of 27% for dry media (initial AWHC = 0%), and obtained a total WAP of 55% for moist media (initial AWHC = 23%). In media comparisons, the incorporation of a wetting agent into a 70% peat/30% bark mix at planting increased the WAP compared to the same media without a wetting agent with nine of the ten irrigation treatments.

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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.