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  • Author or Editor: Jeffrey G. Williamson x
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A wide variety of temperate, subtropical, and tropical fruit crops are grown commercially in Florida. Farm size ranges from large commercial operations exceeding 100 acres to small 1- or 2-acre “estate” farms. Irrigation and fertilization practices vary widely with crop, soil type, and management philosophy. However, many growers are adopting practices such as microirrigation, fertigation, and other technologies, which, if properly used, should reduce water and fertilizer inputs and minimize leaching and runoff of fertilizers and pesticides. Although fertilizer and irrigation recommendations exist for major crops such as avocado (Persea americana), mango (Mangifera indica), and blueberry (Vaccinium spp.), there is little research-based information specific to Florida for many minor crops, including muscadine (Vitis rodundifolia), blackberry (Rubus spp.), sapodilla (Manilkara zapota), guava (Psidium guajava), papaya (Carica papaya), and others. Even where recommendations exist, refinement of irrigation and fertilization practices is needed because of changes in technology.

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Successful blueberry (Vaccinium sp.) cultivation typically requires soils with low pH, high organic matter, readily available iron, and nitrogen (N) in the ammonium form. Growth of blueberry on typical mineral soils (higher pH, low organic matter) is reduced. Although soil pH effects on nutrient availability and uptake are known, it is unclear if the requirement for low soil pH in blueberry production is due to effects on nutrient availability/uptake or is a more direct effect of rhizosphere pH on root function. In addition, it is unclear if the requirement for high organic matter (soil amendments) is related directly to nutrient availability/uptake. Several studies have examined the use of rootstocks to increase soil adaptation of blueberry and some of these rootstocks have been found to increase plant vigor and yield. In particular, we have investigated whether sparkleberry (Vaccinium arboreum)—a wild blueberry species that is adapted to high pH and low organic matter soils—could be used as a rootstock for commercial production of blueberry on mineral soils. Our work indicates that both nitrate (NO3 ) and iron (Fe) uptake and assimilation are greater in sparkleberry compared with southern highbush blueberry [SHB (Vaccinium corymbosum interspecific hybrid)]. This is correlated with increased activity of nitrate reductase (NR) and iron chelate reductase, the rate limiting enzymes for NO3 and Fe acquisition, respectively. Field studies comparing growth and yield of own-rooted vs. grafted ‘Meadowlark’ and ‘Farthing’ SHB in amended vs. nonamended soils are ongoing. In general, own-rooted plants on amended soils exhibit greater growth than own-rooted on nonamended soils, while grafted plants in either soil system exhibit intermediate growth. Yields generally followed this pattern. Our preliminary results suggest that tolerance of SHB to mineral soils is greater when plants are grafted onto sparkleberry than when grown on their own roots. However, growth and yield of grafted plants grown under mineral soil conditions may not equal or exceed that of own-rooted plants grown under optimum soil conditions, at least in the first years after field planting. Longer term studies are necessary to fully evaluate the potential of using sparkleberry and other blueberry species as rootstocks for SHB and northern highbush blueberry (V. corymbosum).

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Nonweighing drainage lysimeters were used to measure seasonal water use of mature ‘Emerald’ southern highbush blueberry (SHB; Vaccinium corymbosum interspecific hybrid) plants grown in pine bark beds and in pine bark amended soil in north central Florida. In the absence of rain, irrigation was applied daily with microsprinklers at ≈120% to 175% of reference evapotranspiration as either single or split applications. Leachate was collected and its volume determined from each lysimeter at 6- to 10-day intervals throughout the study. Water use, expressed as L/plant, was calculated as the difference between the amount of irrigation/rain added to lysimeters and the amount of leachate collected from lysimeters during each measurement period. Average daily water use was calculated for monthly intervals beginning in Apr. 2010 and ending in Sept. 2012. Water use increased rapidly during spring through the final stages of fruit ripening and harvest (May) with peak water use occurring during mid to late summer (July, August, and September). Plants grown in pine bark beds used more water than plants in pine bark amended soil during Apr., May, and Dec. 2010, Feb. 2011, and Mar. 2012, but there were no differences during the periods of highest water use. No differences in water use were observed between single or split-application irrigation treatments. Monthly averages for daily water use during the 30-month period ranged from ≈1.75 L/plant in January to ≈8.0 L/plant in mid to late summer. Mean monthly crop coefficient values during the 30-month period ranged from 0.44 in February to 0.86 in September. Canopy volume, yield, and mean berry weight were unaffected by soil or irrigation treatments.

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Three southern highbush blueberry cultivars (Vaccinium corymbosum hybrids) were mechanically harvested (MH) or hand-harvested (HH) and commercially packed before storage for 14 days at 1 °C in two successive years. MH fruit were softer, had lower ratings for overall appearance, and lost up to 20% more fresh weight than HH fruit after 14 days storage. MH ‘Meadowlark’ had fewer soft fruit (<35%) during storage than either ‘Sweetcrisp’ or ‘Farthing’; however, the latter two cultivars had lower incidences of shrivel and weight loss. Fruit in the 2010 season were more susceptible to bruising than those from the 2009 season; however, soluble solids content (SSC), total titratable acidity (TTA), and ascorbic acid concentration remained constant during storage and between seasons. ‘Meadowlark’ had the highest sugar to acid ratio (25.0). Successful implementation of MH of southern highbush blueberries for fresh market will only be commercially feasible if harvest impacts are further reduced.

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There is increasing interest in red raspberry (Rubus idaeus) production worldwide due to increased demand for both fresh and processed fruit. Although the United States is the third largest raspberry producer in the world, domestic demand exceeds supply, and the shortage in fresh market raspberries is filled by imported fruit from Canada during July and August, and from Mexico and Chile during November through May. The raspberry harvest season is well defined and the perishability of the fruit limits postharvest storage. Winter production of raspberry in tropical and subtropical climates could extend the harvest season and allow off-season fruit production during periods of high market prices. The objective of the current study was to examine growth and yield of red raspberry cultivars grown in an annual winter production system in Florida and Puerto Rico. Long cane cultivars were purchased from a nursery in the Pacific northwestern U.S. in 2002 (`Heritage' and `Tulameen'), 2003 (`Tulameen' and `Willamette'), and 2004 (`Tulameen' and `Cascade Delight') and planted in raised beds in polyethylene tunnels in December (Florida) or under an open-sided polyethylene structure in January-March (Puerto Rico). In Florida, harvest occurred from ∼mid-March through the end of May, while in Puerto Rico, harvest occurred from the end of March through early June (except in 2002, when canes were planted in March). Yields per cane varied with cultivar, but ranged from ∼80 to 600 g/cane for `Tulameen', 170 to 290 g/cane for `Heritage', 135 to 350 g/cane for `Willamette', and ∼470 g/cane for `Cascade Delight'. Economic analysis suggests that, at this point, returns on this system would be marginal. However, increasing cane number per unit area and increasing pollination efficiency may increase yields, while planting earlier would increase the return per unit. The key to success may hinge on developing a system where multi-year production is feasible in a warm winter climate.

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