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between housing developments and production fields using deep fresh water wells. High-impact sprinkler irrigation (4 to 5 gal/min per head) is used during strawberry production for two primary reasons: transplant establishment and freeze protection. For

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Burger, 1997 ), comparatively little research has evaluated the ability of containerized plants to capture sprinkler irrigation water. Irrigation capture is important because containers occupy only a fraction of the production area even when closely

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Abstract

Trickle and sprinkler irrigation systems were effective in attaining an average fruit yield of 1660 g/m of row of red raspberry (Rubus idaeus L.) in eastern South Dakota. Water requirements averaged 68 cm with an average irrigation requirement of 33 cm.

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Six field studies were conducted from 1980-88 to evaluate the response of cabbage (Brassica oleracea L., Capitata group) to sprinkler irrigation and sprinkler-applied N fertilizer on a coarse-textured soil. The plots were irrigated using a modified self-moving lateral sprinkler irrigation system that applied five levels of water and five levels of N (liquid NH4NO3) in specified combinations of central composite rotatable design. Cabbage yields were significantly increased by water and N applications in all experiments. The N rates predicted for maximum yield exceeded typical cabbage N fertilizer recommendations. However, the above-average plant populations used in these studies resulted in above-average yields and plant N accumulation. Deficit and excess irrigation produced negative results. Generally, cabbage production was optimized and N losses to the environment were minimized when crops were irrigated for evapotranspiration (ET) replacement. However, even when irrigated for ET replacement, these data demonstrate the potential for N leaching at high N rates, presumably as a result of rainfall.

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Nitrogen fertilizer rates and timings were reexamined for potatoes (Solanum tuberosum L.) under sprinkler irrigation with scheduling by soil water potential. Four potato cultivars were grown on a silt loam soil in eastern Oregon in 1992, 1993, and 1994. Potatoes were submitted to six treatments: four N fertilizer rates (0, 135, 200, and 270 kg·ha-1) and two split application treatments (67 kg·ha-1 applied three times, and 40 kg·ha-1 applied five times). The crop was irrigated when the soil water potential at 0.2-m depth reached -60 J·kg-1. No more than the accumulated evapotranspiration was replaced at each irrigation. Over 3 years, the cultivars had similar responses to N rates and N timing. In 1992, following alfalfa, tuber yield was not responsive to N fertilization. In 1993 and 1994, following wheat, tuber yield was maximized by N at 211 and 175 kg·ha-1. Split applications of the N fertilizer did not increase tuber yield in any year. In 1993 and 1994, the highest tuber specific gravity was obtained with no N fertilization. Nitrogen rates above the optimum resulted in darker frying tubers in 1992 and 1993. The N rates maximizing tuber yield in this study were lower than the rates recommended in the university fertilizer guides.

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The influence of supplemental sprinkler irrigation on fruit color of `Oregon Spur Delicious' (Trumdor) apples (Malu×domestica Borkh.) was evaluated in the area of Lleida (NE Spain) over a 3-year period. Cooling irrigation was applied for 2 hours daily for 25-30 days preceding the harvest. Three treatments were evaluated: 1) control without overtree sprinkler irrigation; 2) sprinkler irrigation applied at midday; and 3) sprinkler irrigation applied at sunset. Fruit color was significantly affected by the cooling irrigation and also by the weather of the particular year. Increased red color and higher anthocyanin content resulted from sprinkler irrigation, especially when applied at sunset. At harvest, anthocyanin content was correlated with a*/b* and hue angle, suggesting that the colorimeter measurements could provide a nondestructive estimate of anthocyanin content.

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Economic analyses compared the returns of weed control methods for drip and sprinkler irrigated celery (Apium graveolens L. `Sonora'). The nine treatments included an untreated control, cultivation as needed for weed control, a pre-emergent herbicide (trifluralin), and six post-emergent herbicides. The effect of each treatment on weed control, yield, crop value, cost of control, costs for additional hand-weeding, net return, and dollar investment (marginal rate of return) was determined. The treatments that reduced weed populations under drip and sprinkler irrigation also increased yield, net returns, and rate of returns. Effective weed control reduced the additional costs of hand-hoeing the weeds not killed by herbicides, resulting in greater net return. The net returns of weed control were even greater when celery was drip irrigated than when sprinklers were used. In 1998, the sprinkler irrigated field returned $1148 to $3921/ha, compared with -$5984 for the untreated control. Net returns for drip irrigation were much higher, ranging from $3904 to $9187/ha compared with -$8320 for the untreated control. Net returns were also higher in 1999, ranging from $2466 to $5389 when weeds were controlled compared with a net loss of $5710 for the untreated control in the sprinkler irrigated field. The returns on the drip-irrigated field were much higher, from $6481 to $8920 when weeds were controlled, compared with -$8046 for the untreated control. The associated returns for every dollar invested (marginal rate of return) in the non-dominated treatment (more return and lower cost) ranged from 52% to 156% for sprinkler irrigation, and 59% to 144% for drip irrigation in 1998. In 1999, the rate of return for each dollar invested ranged from 104% to 324% for sprinkler and 2.4% to 321% for drip irrigated fields.

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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.

Open Access

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

Low vol overtree sprinkler irrigation was used on ‘Starkrimson Red Delicious’ apples during 2 successive growing seasons to determine the potential for moderating environmental extremes and reducing moisture stress through evaporative cooling. Irrigation, applied when air temp exceeded 87°F, substantially cooled plant tissues. In addition a residual cooling effect from evaporation of irrigation water following application was evident. The fruit exhibited the greatest amount of cooling (avg of 12.1° and 8.1°F in 1969 and 1970, respectively) because evaporation cooling negated radiation heating which normally caused fruit temp to be well above air temp. Cooling effects were proportional to length of operation of the irrigation system.

Open Access