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A.L. Shober, K.A. Moore, C. Wiese, S.M. Scheiber, E.F. Gilman, and M. Paz

Agriculture hardiness zones 8b, 9a, and 10b. Table 3. Mean growth index and root to canopy spread ratio ( n = 6) for selected Florida native and non-native shrub species established in the landscape under low-volume irrigation [3 L (0.8 gal) per plant] over

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Etaferahu Takele, Jewell L. Meyer, Mary L. Arpaia, David E. Stottlemyer, and Guy W. Witney

The effect of integrated applications of various irrigation and fertilization rates on productivity (yield and size) and returns of the `Hass' avocado (Persea americana Mill.) have been analyzed from 1987 to 1991 in western Riverside County. Eighteen treatment combinations comprised of three irrigation levels [80%, 100%, and 120% crop water use (ETc)], three N fertilizer levels (0.16, 0.7, and 1.4 kg/tree per year), and Zn (0 and 0.2 kg/tree per year) were included in the analysis. Using a partial budgeting procedure, returns after costs were calculated for each treatment combination. Costs of treatments, harvesting, hauling, and marketing were subtracted from the value of the crop. The value of the crop was calculated as the sum of crop returns in each size category. Three years of data on the relationship between irrigation and N showed 1) irrigating at 80% ETc would be ineffective even at very high water prices; 2) for groves where 100% ETc is sufficient, its application with either low or medium N would be beneficial; and 3) at higher irrigation (120% ETc), N application should be at or beyond the medium level.

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Mark Rieger

Spring frost events reduce fruit production in the southeastern United States more than any other factor, with some losses occurring in 5 out of 7 years. Orchard heaters, wind machines, and overhead irrigation are sound methods of reducing losses, but their relatively high cost is a major deterrent for fruit growers (Castaldi, 1990). A potentially leas-costly and more water- efficient approach to frost protection is overtree microsprinkling. Microsprinkler irrigation was applied either beneath or onto canopies of 4-year-old `Loring' peach [Prunus persica (L.)] trees at a rate of 38 liters/h per tree to evaluate the relative efficacy of low-volume undertree and overtree microsprinkling for frost protection. Overtree microsprinkling maintained flower bud temperatures 2C during a calm, radiative frost on 20-21 Mar. 1990 (minimum air temperature -4.4C), whereas undertree sprinkling provided 0.5C of air temperature elevation at a comparable height in trees (2 m). Twelve days later, fruit set was lower for nonirrigated and undertree-irrigated trees (none to one fruit/m of shoot length) than for trees irrigated with overtree microsprinklers (eight to nine fruit/m of shoot length). Economic analysis showed that capital costs of overtree microsprinkler systems increased annual costs of peach production by 8% to 13%, which required increased yield (or price per unit yield) of 17% to 20% before profits exceeded those of nonirrigated orchards, assuming all else equal. The estimated 1% increase in annual production costs of overtree microsprinkling compared to undertree microsprinkling appears to be justified by the increased efficacy of the overtree system.

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AK. Alva and T.A. Obreza

Deep aquifer water, which contains high levels of bicarbonate and Ca, is used predominantly for citrus irrigation. Changes in soil pH and Mehlich 1 extractable Ca concentrations were examined inside and outside the microsprinkler-wetted zone in 3- to 5-year-old citrus groves on three soils. Soil pH at 0 to 15 cm inside the wetted zone was 0.4, 0.9, and 1.3 pH units higher than that outside the wetted zone in Immokalee, Myakka, and Holopaw sands, respectively. This pH increase was due to the addition of bicarbonate in the irrigation water. Extractable Ca concentrations were also about two-fold higher inside compared to those outside the wetted zone at depths of O to 15 and 15 to 30 cm. With young trees, a majority of the roots are within the microsprinkler-wetted zone; therefore, soil samples should be taken inside the wetted zone for measuring soil pH and status of plant nutrients.

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Dariusz Swietlik

The public is increasingly concerned with the danger of ground water pollution with fertilizer nitrogen and other chemicals. This is because slow water movement in underground aquifers assures the long lasting existence of contaminants. Citrus orchards commonly are heavily fertilized with nitrogen and other mineral nutrients. Fertigation through a low volume irrigation system is a promising new method of efficient use of fertilizer materials because it places mineral nutrients only in the wetted zones where roots are most active. Preliminary studies in Texas indicate that applying nitrogen fertilizers through a low volume irrigation system is a potentially powerful tool in minimizing N fertilizer leaching. When coupled with partial sodding in close tree proximity further reductions in NO3 leaching may be achieved presumably through uptake into the cover plants and/or indirectly by enhancing biological fixation in the soil. Other potential benefits of frequent N fertigations in citrus orchards will also be discussed based on the experimental data collected in various parts of the world.

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James W. Paterson

The effectiveness of varying rates and timing of applied primary plant nutrients as a completely soluble N-P-K fertilizer through a drip/trickle low volume irrigation system was studied during 1991 on eggplant (Solanum melongena cv. Harris Special Hibush). Before the drip irrigation tubing and black plastic mulch were laid on a coastal plain sandy loam soil, plots were treated with 0, 22, 45, and 67 kg ha-1 of nitrogen (N), phosphate (P2O5) and potash (K20). The higher rates of preplant fertilization did have a significant beneficial effect on total seasonal yields of quality eggplants. The preplant treatments also had an influence on mid and late season production. As the frequency of drip/trickle applied primary plant nutrients increased up to 6 seasonal applications, the total quality fruit production substantially increased. Frequency of applications also had an influence on seasonal yields. Applying increased rates of the primary plant nutrients at a low seasonal frequency of 3 applications had little influence on increasing total quality yields of eggplants. Individual quality fruit was significantly heavier from plants which received 5 to 6 applications of the soluble N-P-K fertilizer than from plants which received no fertilizer through the drip/trickle irrigation system for the season.

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Jeffrey G. Williamson and E. Paul Miller

Bearing `Misty' and `Star' southern highbush blueberries were grown on pine bark beds and fertilized at three rates using granular and liquid fertilizers with a 3–1–2 (1N–0.83K–0.88P) ratio. Granular fertilizer was applied 8 times per year at 4-week intervals beginning in April and continuing through October. Liquid fertilizer was applied with low volume irrigation 16 times per year at 2-week intervals during the same period. During the growing season, irrigation was applied at 2- to 3-day intervals in the absence of rain. A 2 cultivar × 2 fertilizer type × 3 fertilizer rate factorial arrangement of treatments was replicated 8 times in a randomized complete-block design. All fruits were harvested from single-plant plots at 3- to 4-day intervals. Canopy volume was not affected by fertilizer type, but fruit yield was slightly greater for granular than for liquid fertilizer treatments. In 2003, fruit yield of 2.5-year-old `Misty' and `Star' plants increased with increasing fertilizer rates up to the highest rate tested (50 g N/plant/year). Similarly, in 2004, fruit yields increased with increasing fertilizer rates up to the highest rate (81 g N/plant/year). Root distribution was limited to the 12-cm-deep layer of pine bark with very few roots penetrating into the underlying soil. The positive growth responses of blueberry plants to high fertilizer rates in pine bark beds suggests that soluble fertilizer was leached through the pine bark layer into the soil below the root zone. More frequent, lighter applications of soluble fertilizers, use of slow-release or controlled-release fertilizers, and careful irrigation management may improve fertilizer use efficiency of blueberry plantings on pine bark beds.

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Brent A. Holtz

Pistachio (Pistacia vera) was successfully introduced into California and initially touted as a tree nut crop with no disease or insect pests. Unfortunately, these expectations were dashed as a number of diseases and pests followed commercial plantings, making plant protection practices integral to production. Verticillium wilt (Verticillium dahliae) devastated early plantings but is now controlled with the use of resistant rootstocks. Botryosphaeria blight (Botryosphaeria dothidea) and alternaria late blight (Alternaria alternata) are recently arrived foliar fungal diseases that blight fruit clusters and defoliate trees, respectively, and multiple fungicide applications are needed for control. The conversion to low volume irrigation systems, specifically to drip or buried drip, has reduced disease. Pruning out botryosphaeria blight infections has reduced overwintering inoculum and disease, while current research aims at accurately predicting infection events to increase fungicide efficacy. A number of hemipteran insect pests have been associated with epicarp lesion: spring treatments have been replaced with dormant carbaryl and oil applications which are less toxic to beneficial insects while controlling phytocoris (Phytocoris californicus and P. relativus) and soft scale pests. Early season insect damage can be tolerated because trees compensate by maturing a higher percentage of remaining fruit kernels. Some mirid (Calocoris spp.) pests can be effectively reduced by eliminating alternate hosts in an effective weed control program. If lygus (Lygus hesperus) populations are present, weeds should not be disturbed from bloom until shell hardening to prevent movement by insects into the trees where feeding can result in epicarp lesion. Stink bugs (Pentatomidae) and leaffooted bugs (Leptoglossus clypealis and L. occidentalis) can penetrate the hardened shell and cause internal nut necrosis along with epicarp lesion. Trap crops are used to monitor pest populations in order to develop treatment thresholds. Degree-day based timing of treatments increase insecticide efficacy for the control of navel orangeworm (Amyelois transitella) and obliquebanded leafroller (Choristonuera rosaceana), but navel orangeworm populations are more effectively managed by destroying unharvested over wintering fruit. Bacillus thuriengiensis sprays, liquid-lime-sulfur, and biological control show promise in controlling obliquebanded leafroller.

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nature is stronger in rural surroundings. In particular, urban boys did not necessarily consider themselves to be part of nature and did not see that vegetation had any meaning for them. Establishment of Florida Shrubs via Low-volume Irrigation Previous

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Jeffrey G. Williamson and Jonathan H. Crane

include monitoring weather conditions to avoid nutrient applications immediately preceding a rainfall event and using calibrated low-volume irrigation chemical injection ( Migliaccio et al., 2006 ). Widespread adoption of leaf sampling and phenological