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  • Author or Editor: G. A. Clark x
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Proper management of vegetable drip-irrigation systems requires knowledge of soil hydraulic characteristics, plant-growth and water-use characteristics, and evaporative demand. The resultant schedule must integrate these properties and conform to existing irrigation system and cultural constraints. Irrigation management must be coupled with the fertilizer management program to avoid excessive water applications that leach plant nutrients. Because drip irrigation applies water to discrete locations along the plant row, limited irrigated areas can result, and this is an important consideration for irrigation system design, cultural practices and management, and irrigation system operation and management.

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Proper design and installation are essential to provide a drip irrigation system that can be managed with minimal inputs and maximum profit. Because drip irrigation can apply precise amounts of water and chemicals, constraints associated with the plants, soil, water supply, and management must be considered in the design, installation, and management processes.

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The injection of chemicals into irrigation systems is discussed in terms of injection systems, concentration injections, bulk injections, quantity of chemicals to be injected, injection system calibration, and injection periods. Sufficient clean-water flush time should be scheduled to purge irrigation lines of injected chemicals unless it is desired to leave that particular chemical in the irrigation system for maintenance purposes. Chemical injection rates vary with desired chemical concentration in the irrigation water, concentration of the stock solution, volume of chemical to be injected, and duration of each injection. All injection systems should be calibrated and maintained in proper working order. This information is presented to assist irrigation system designers and operators with chemigation system design, scheduling, and management.

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Combinations ofvarious vegetable crop species grown in multiple-cropping sequences using microirrigation on a sandy soil were evaluated for production potential and changes in normal cultural management An initial fall-season fresh-market tomato crop was followed immediately by a winter-season crucifer crop (cauliflower, broccoli, or cabbage), which was followed by a spring-season cucurbit crop (cucumber, zucchini squash, or muskmelon). Studies were conducted over a 3-year period in southwestem Florida. Results showed that when cropping sequences were compared on a basis of a derived relative value index (RVI), the sequence of tomato-cauliflower-zucchini squash significantly outperformed other sequences. Several management concerns particular to the production system (crop residue removal and interference, plastic mulch deterioration and damage, and weed control) were identified and discussed. The potential savings when cropping sequences are compared to individual crop production resulted in net savings (dollar savings less additional production costs) that ranged from $565 to $1212/acre ($1396 to $2993/ha) and $614 to $1316/acre ($1516 to $3251/ha) for the 1986-87 and 1988-89 seasons, respectively.

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Three vegetable irrigation systems, semi-closed subirrigation (seepage), fully enclosed subirrigation (seepage), and drip irrigation, were evaluated for use on sandy soils with naturally high water tables to determine comparative irrigation costs for tomato production. Investment, fixed (ownership), and variable (operating) costs were estimated for each irrigation system. The investment costs of the drip irrigation system were significantly greater than those for the semi-closed and fully enclosed irrigation systems. The variable costs, however, for the semi-closed system were considerably less than those for the fully enclosed and drip irrigation systems. The semi-closed irrigation system, therefore, was determined to be the least-cost tomato irrigation system under present fuel cost and nonlimiting water supply conditions.

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Experiments were conducted to determine if the seedling hypocotyl elongation and petal abscission assays could be used to identify differences in ethylene sensitivity among seedling geranium (Pelargonium ×hortorum) cultivars. When seedlings of six geranium cultivars were germinated and grown in the dark in the presence of the ethylene biosynthetic precursor 1-aminocyclopropane-1-carboxylic acid (ACC) at various concentrations, they exhibited the triple response (measured as reduced hypocotyl length). While seedlings from all six cultivars were sensitive to ACC, `Scarlet Elite' seedlings were most sensitive, and `Multibloom Lavender', `Elite White' and `Ringo 2000 Salmon' seedlings were the least sensitive when germinated and grown on 20 mm [2022 mg·L-1 (ppm)] ACC. Florets representing three developmental stages of each of the six cultivars were exposed to 1 μL·L-1 of exogenous ethylene for 0, 30, or 60 min to determine if differences in cultivar sensitivity could be determined for petal abscission. Of the six cultivars tested, `Ringo 2000 Salmon', `Multibloom Lavender' and `Elite White' were the least ethylene sensitive. Florets were also self-pollinated to test for cultivar differences in ethylene synthesis and subsequent petal abscission. Ethylene production and petal abscission were both promoted in self-pollinated florets compared to nonpollinated florets. `Ringo 2000 Salmon', `Multibloom Lavender' and `Elite White' florets produced similar amounts of ethylene as all other cultivars, but abscised fewer petals after pollination. Our results indicate that the seedling hypocotyls elongation assay may be used to identify geranium cultivars with reduced sensitivity to ethylene. The data also suggest that genetic variability exists among geraniums for both ethylene sensitivity and biosynthesis.

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The Florida horticulture industry (vegetables, ornamentals, citrus, and deciduous fruit), valued at $4.5 billion, has widely adopted microirrigation techniques to use water and fertilizer more efficiently. A broad array of microirrigation systems is available, and benefits of microirrigation go beyond water conservation. The potential for more-efficient agricultural chemical (pesticides and fertilizer) application is especially important in today's environmentally conscious society. Microirrigation is a tool providing growers with the power to better manage costly inputs, minimize environmental impact, and still produce high-quality products at a profit.

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The yield of three generations of virus-tested plants of `Beauregard' sweetpotato (Ipomoea batatas) was assessed in Louisiana over a 4-year period in 15 yield trials. Treatments included virus-infected foundation `Beauregard', virus-tested `Beauregard' mericlone, B-63 [generation 1 (G-1)], and three generations of B-63 (G-2, G-3 and G-4). Generations refer to the number of continuous years virus-tested plants are grown in the field. Use of G-2 virus-tested `Beauregard' transplants increased yields of U.S. no. 1 grade roots by 16% in comparison with virus-infected, foundation `Beauregard'. Total marketable yield was also higher (11%) using B-63 G-2 transplants in comparison to virus-infected, foundation `Beauregard'. Use of B-63 (G-1), G-3 and G-4 generation transplants did not increase yields in any grade in comparison to virus-infected, foundation `Beauregard' by planting plots amidst virus-infested sweetpotato fields. Generation one B-63 transplants were greenhouse grown and often appeared less robust after planting. Yet we were unable to show significant yield differences between greenhouse derived B-63 (G-1) and field-grown B-63 (G-1) in separate tests; other factors may be involved.

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