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Bielinski M. Santos, Teresa P. Salame-Donoso and Alicia J. Whidden

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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Jeff B. Million and Thomas H. Yeager

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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C.A. Sanchez, R.L. Roth and B.R. Gardner

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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I. Iglesias, J. Graell, G. Echeverría and M. Vendrell

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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Erik B.G. Feibert, Clinton C. Shock and Lamont D. Saunders

Onion yield and grade were compared under sprinkler, subsurface drip, and furrow irrigation in 1992, 1993, and 1994. Furrow-irrigated onions were planted on two double rows on 1.12-m-wide beds at 352,000 seeds/ha. Sprinkler- and drip-irrigated onions were planted in nine single rows on a 2.24-m-wide bed at 432,100 seeds/acre. Drip plots had three drip lines buried 0.10 m deep in each 2.24-m bed. Soil water potential at 0.2-m depth was measured by tensiometers and granular matrix sensors (Watermark Model 200SS, Irrometer Co., Riverside, Calif.). Furrow irrigations were started when the soil water potential at the 0.2-m depth reached –25 kPa. Drip-irrigated onions had soil water potential at the 0.2-m depth kept wetter than –25 kPa by daily replacement of crop evapotranspiration (Etc). Sprinkler irrigations were started when the accumulated Etc reached 25 mm. Sprinkler irrigation resulted in significantly higher onion yield than furrow irrigation in 1993 and 1994. Sprinkler irrigation resulted in higher marketable onion yield than furrow irrigation in 1993. Drip irrigation resulted in significantly higher onion yield than furrow irrigation every year. Drip irrigation resulted in higher marketable onion yield than furrow irrigation in 1992 and 1994. Marketable onion yield was reduced in 1993 due to rot during storage.

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Edmund J. Ogbuchiekwe and Milton E. McGiffen Jr.

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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Richard C. Beeson Jr. and Thomas H. Yeager

Marketable size plants of sweet viburnum (Viburnum odoratissimum Ker-Gawl.), waxleaf ligustrum (Ligustrum japonicum Thunb.), and azalea (Rhododendron spp. L. `Southern Charm') grown in 11.4-L containers were irrigated with overhead impact sprinklers at container spacings ranging from 0 to 51 cm apart. Water reaching the substrate surface was quantified and the percentage of that applied calculated as percent capture (% capture). Percent capture is defined as the percentage of water falling above the plant within a projected vertical cylinder of a container that reaches the substrate surface. For all species, % capture increased linearly with the decline in adjacent canopy interaction, which results from canopies extending beyond the diameter of a container. Increases in total leaf area or leaf area outside the cylinder of a container, in conjunction with increasing distance between containers, were significantly (P < 0.05) correlated with increases in % capture for ligustrum and viburnum. Increases in % capture partially compensated for decreases in percentage of production area occupied by viburnum containers as distances between containers increased, but not for the other two species. Under commercial conditions, optimal irrigation efficiency would be achieved when plants are grown at the minimum spacing required for commercial quality. This spacing should not extend beyond the point where canopies become isolated.

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Maria Claudia Dussi, David Sugar, Anita Nina Azarenko and Timothy L. Righetti

Over-tree sprinkler irrigation cooling treatments were applied to `Sensation Red Bartlett' pear trees during the final 30 days of fruit maturity in 1992 and 1993 when orchard air temperatures were >29 °C. Fruit from cooled trees were more red and less yellow than fruit from noncooled trees, resulting in lower hue values by the middle of the harvestable maturity period in both years of study. In 1992, cooled fruit had a greater portion of the fruit surface covered with red blush than fruit that were not cooled. Fruit firmness decreased more rapidly in fruit from cooled trees than in fruit from noncooled trees, indicating advanced maturity. Accordingly, cooled fruit should be harvested earlier than noncooled fruit to maintain postharvest quality. Differences between cooled and noncooled fruit with respect to hue, surface blush, and rate of firmness loss were more pronounced in a warm season requiring frequent cooling than in a cooler season.

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Nabila S. Karam and Alexander X. Niemiera

The influence of intermittent and continuous irrigation on the growth, substrate nutrient accumulation and leaching from container-grown marigolds was determined. During a three week period. Tagetes erecta L. `Apollo' in a pine bark substrate received 12 irrigations. Each irrigation allotment was applied intermittently (multiple applications) or continuously (single application). Irrigation occurred when bark reached a targeted water content; irrigation water contained a complete nutrient solution. Leachates were cumulatively collected for each container and analyzed for N; plant dry weight. size, and nutrient composition were determined. Compared to continuously irrigated plants, intermittently irrigated plants had 43% greater root dry weight, 0.7% greater N concentration, and 43% more N leached from the substrate. Shoot mass. size. K, and P concentrations, substrate (pour-through extraction) and leachate N concentration were unaffected by irrigation method. Results demonstrated that. compared to conventional irrigation practices, intermittent irrigation was an effective method to reduce fertilizer effluent and increase N absorption for container-grown plants.

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David R. Bryla and Robert G. Linderman

and Cohn) J. Schröt. was most severe when trees were irrigated by microsprays and similar when trees were irrigated by sprinklers and drip. Clearly, pathogenic responses to irrigation application may vary depending on the crop, site conditions, and the