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Native plants for ecosystem restoration are commonly grown in containers in greenhouses. Within greenhouses, overhead irrigation is the most widely used system to irrigate plants ( Leskovar, 1998 ). Overhead irrigation systems are chosen for their

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the former industry standard furrow irrigation has been the ability to precisely apply small amounts of water more frequently to maintain these ETc targets. Overhead irrigation, including both center pivot and linear move systems, is a technology that

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to use overhead irrigation instead of drip irrigation, which has been done successfully on farms in Spain (L. Martin-Closas, personal communication). Overhead irrigation systems for possible use with BDM include center pivot, linear move, traveling

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container seedling production. Overhead irrigation is the most widely used form of irrigation in tree seedling nurseries ( Landis et al., 1989 ; Leskovar, 1998 ) as a result of its simplicity, low-cost installation, and capacity to reduce toxic buildup of

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study indicated that using a free chlorine concentration less than 2.5 mg·L −1 , applied daily through overhead irrigation, should not adversely affect the growth or appearance of woody shrubbery nursery liners. Because our research was conducted in the

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Proper irrigation management is essential for producing quality container-grown woody ornamentals and reducing off-site runoff. Research has shown that tensiometers can be used as an effective tool to schedule irrigation for woody ornamentals. The objective of this experiment was to compare the effect of cyclic and tensiometric irrigation methods on growth of lantana. Lantana camara `New Gold' liners were established in a 3 pine bark: 1 peat:1 mason sand (by volume) medium. Low-tension switch tensiometers were compared to scheduled overhead [one time a day (1×) at 0600 and cyclic irrigation three times a day (3×) at 0600, 1200, and 1800] for the production of 1-gallon lantana plants. Three low-tension tensiometers (1/block) were set at 7 cb and allowed to irrigate over a 12-hour period. Three separate planting dates occurred and then terminated after ≈7 weeks. Tensiometric irrigation increased root and shoot growth compared to scheduled irrigation for the 24 May 1999 harvest date. Cyclic irrigation produced plants with shoot and total root weights >1× and tensiometer treatments for the September harvest date. Tensiometers sharply reduced irrigation requirements compared to scheduled irrigation volume by at least 50% of the 1× and 3× treatments weekly. Analysis of nutrients in leachate for June indicated increased B and Fe concentrations in the 3× irrigation treatment. Lower concentrations of Ca, Mg, and Na were measured in August. Lantana growth was acceptable for all irrigation treatments and harvest dates.

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Elaeagnus pungens Thunb., Ligustrum japonicum Thunb., Photinia ×fraseri `Red Top', and Rhododendron sp. `Fashion' (azalea) growing in 10.4-liter containers were irrigated only at dawn with overhead impact sprinklers or pulse-irrigated three or four times each day with a drip system. Plant water potential was measured diurnally each week for 24 weeks, and growth was measured at the end of the growing season in December. Overhead irrigation resulted in less growth of all species than plants maintained near 100% container moisture with pulse irrigation. With the exception of photinia, more growth was associated with significantly lower daily accumulated water stress. Water stress of overhead-irrigated plants was generally not severe enough to cause stomata1 closure.

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Abstract

Fruit and vegetative growth of 21-year-old grapefruit (Citrus paradisi Macf.) trees on well-drained sandy soil was studied in central Florida. Drip, microsprinkler, and overhead sprinkler irrigation was compared at two levels of irrigation (150 and 450 mm·year−1). Significant differences in leaf area, fruit size, fruit growth, new flush growth, and canopy area were found with different irrigation systems applying similar amounts of water. Growth was improved by irrigation even in a year of high rainfall (1410 mm). With mature trees, drip systems promoted the least growth, while overhead sprinkler systems promoted the most. Leaf fresh and dry weights and individual leaf areas in the overhead sprinkler treatments were 40% to 50% greater than in the drip or nonirrigated treatments, while specific leaf weight and leaf water content per unit dry weight were similar for all treatments. Final fruit size and tree canopy area were 9% to 20% greater in the overhead sprinkler treatments than in the corresponding drip or nonirrigated treatments. Responses to microsprinklers were generally intermediate between the overhead sprinkler and the drip treatments. Because of the low soil area coverage, applying water at the higher rate with the drip system did not improve growth as well as the overhead system at the lower rate. With mature grapefruit trees under central Florida conditions, systems providing greater soil area coverage gave better leaf and fruit growth than systems providing less soil coverage.

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Abstract

Water relations responses of 21-year-old grapefruit trees (Citrus paradisi Macf.) irrigated by three types of irrigation systems were compared. Drip, undertree microsprinkler, and overhead sprinkler with application levels of 150 and 450 mm of water per year were compared. Leaf water potential, stomatal conductance, and soil water status were measured under field conditions on a deep, well-drained sandy soil in central Florida. In the early part of a dry spring period, there were no differences in midday or early morning leaf water potential, but, by the end of this period, significant differences in leaf water potential were found among all three irrigation treatments. Highest leaf water potential and stomatal conductance values were maintained in the overhead sprinkler blocks. No midday stomatal closure was observed under the conditions of this study. Relationships among diurnal leaf water potentials, vapor pressure deficits, and stomatal conductance showed hysteresis; this affected the correlations among these factors. Greater water stress occurred in trees irrigated with drip than in trees irrigated with overhead sprinkler systems, but responses to microsprinklers were generally intermediate between the overhead sprinkler and the drip treatments. In an area with high rainfall and sandy soils, increased irrigation coverage can reduce leaf water stress.

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Abstract

It has been observed that overhead irrigation does not cause cracking of sweet cherries (Prunus avium l.) to the same extent as a rain of equal duration. A series of simulated rain-overhead irrigation comparisons was made to test the hypothesis that the difference observed could be due to the dissolved salt content of irrigation waters. Although the quality of the irrigation waters selected were quite high (conductivity of 0.175 millimhos/cm or less), the cracking index of cherries wetted with irrigation water was consistently less than with deionized water. The results reemphasize the marked effect of even small amounts of dissolved salts, particularly the divalent cations, on reducing cracking of sweet cherry fruits.

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