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- Author or Editor: Jonathan H. Crane x
Lateral branches arising from the primary bud complex on limbs of containerized `Gefner' atemoya (Annona squamosa L. × A. cherimola Mill.) plants were removed to determine the influence of branch regrowth on the crotch angle. Pruning the lateral branches to a stub (cl cm) was more effective in inducing regrowth and increasing branch angle of the regrowth than stripping lateral branches by hand. Following lateral branch removal, regrowth did not develop from every node along a stem axis. In a second study, the angle of branch regrowth from tagged nodes following pruning of lateral branches was determined. The mean crotch angle of the primary lateral branches was 58°. Regrowth from the second and third supernumerary buds within each node produced branches with an average crotch angle of 72° and 88°, respectively. The largest increase in attachment angle following pruning was obtained at nodes with narrow primary lateral branches and at nodes located closest to the base of a major axis. The increase in branch crotch angle was not correlated with the size of the preceding lateral branch at a node. These results indicate that pruning off lateral branches with narrow crotch angles may be performed during training atemoya plants to produce scaffold limbs from supernumerary buds within the same nodes with desirably wide crotch angles.
Abstract
The response of 2- to 3-year-old ‘Tifblue’ rabbiteye blueberry (Vaccinium ashei Reade) plants to periodic flooding of different durations and seasons was studied under field conditions in 1985 and 1986. Soil redox potentials (Eh) decreased to between 0 and −300 mV within 2 days of flooding and recovered to preflood levels (200 to 300 mV) within 8 to 10 days after flooding release. Plants survived 2-day (four periods) and 7-day (two periods) spring flooding treatments, whereas losses of 17% to 100% occurred after two 2- to 15-day summer flooding episodes. Most (83%) plants survived 106 to 117 days of spring flooding, while 33% and 0% survived 78 and 90 days of summer flooding, respectively. Generally, leaf area, percent fruit set, and yields decreased after two 7-day spring flooding periods, whereas the number of flower buds formed decreased by 38% to 70% with as little as two 2-day summer flooding periods. Stomatal conductance and transpiration decreased after the onset and increased after the release of the two 2- and 7-day summer flooding treatments, but remained low for the 15-day (two periods) and 78-day treatments. The effects of periodic flooding on plant survival, stomatal conductance, and the number of flower buds formed were similar to those found for continuously flooded plants in a previous study.
Abstract
The response of 3-year-old ‘Woodard’ rabbiteye blueberry (Vaccinium ashei Reade) plants to 0, 5,15, 25, and 35 days of flooding during spring and summer of 1984 and 1985 was studied under field conditions. Soil oxygen diffusion rate (ODR) and redox potential (Eh) of flooded plots were significantly lower than those of unflooded plots within 2 days of flooding. After plots were released from flooding, soil Eh recovered to control levels within 10 days but ODR did not. Almost 100% of the plants survived flooding treatments in 1984, whereas plant survival decreased to 83% after 25 days of spring and 67% after 5 days of summer flooding in 1985. Stem elongation and leaf expansion were inhibited after about 15 days of spring and 7 days of summer flooding. The number of flower buds formed during the fall was reduced by about 30% and 70% after as little as 5 days of summer flooding in 1984 and 1985, respectively. Fruit set decreased by 13% and 29% after 25 days of spring flooding in 1984 and 1985, respectively. Yields were not consistently affected by spring flooding, but decreased significantly after 35 days in 1984 and 25 days in 1985.
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.
Carambola (Averrhoa carambola L.) is native to the humid tropics of southeastern Asia, where it bears fruit year-round. In south Florida, winter conditions (strong winds and night temperatures below 15 °C) repress growth and flowering of the main commercial cultivar, Arkin, and fruit is produced from July to February. Off-season fruit would reach premium prices. We have previously demonstrated that selective pruning stimulates flowering of carambola at any time of the year. However, flowers produced during cool, windy weather have consistently failed to set fruit. This study was conducted in 1994–1995 to determine whether protected cultivation would help obtain off-season fruit. Four-year-old `Arkin' trees growing in 80-L containers were placed in a glasshouse or outdoors and pruned in November or December to force flowering during December–January. Glasshouse night temperatures during the winter were above 20 °C. All trees flowered in response to pruning. Outdoor trees produced less than one fruit per tree in late March to late April. Glasshouse trees produced 2.3 to 6.1 fruit per tree, 2 to 3 weeks earlier than trees outdoors. In the glasshouse, more than 98% of fruit were seedless, whereas all fruit produced outdoors were seeded. Production of seedless fruit indoors was achieved in the absence of insect pollinators, and yields were low compared to those of outdoor trees during the summer (at least 25 fruit per tree). We speculate that, under protected cultivation, the use of synthetic bioregulators during anthesis and insect pollinators may help increase production of off-season seedless and seeded fruit, respectively.
Abstract
The relationship of root (RLp) and stem hydraulic conductivity (SLp), root electrolyte leakage (EL), and stomatal conductance (gs) to flooding was investigated using 2-year-old ‘Tifblue’ and ‘Woodard’ rabbiteye blueberry (Vaccinium ashei Reade) plants. Soil redox potentials (Eh) decreased to about — 225 mV within 4 to 10 days of flooding, whereas Eh of unflooded soils were always > 400 mV. Root hydraulic conductivity decreased by 44% to 60%, compared to that of unflooded plants after 4 to 6 days of flooding in two of three experiments, decreasing by 29% to 81% by the end of 2 to 3 weeks. Root electrolyte leakage increased and SLp decreased after 6 to 10 days of flooding. Stomatal conductance decreased by 49% to 93% compared with that of unflooded plants after 4 to 6 days of flooding. Decreases in RLp and gs for flooded plants occurred concomitantly and are two of the earliest physiological responses of rabbiteye blueberry plants to flooding.
Abstract
Flooding damage causes millions of dollars in losses to horticultural crops every year. Plantings established on sites with poor drainage and/or an impervious soil layer may flood periodically after heavy rainfall or excessive irrigation. Planting sites with lowlying areas or where site preparation is inadequate for drainage of excess water add to the problem. Poor soil aeration associated with flooding may induce numerous soil and plant changes that adversely affect plant survival, growth, development, and yield. Organic and inorganic soil toxins may accumulate in flooded soils, adversely affecting plant metabolism and physiology.
This article assesses the profitability of a hypothetical 5-acre tahiti lime (Citrus latifolia) orchard in southern Florida in the presence of citrus canker (Xanthomonas axonopodis pv. citri) and citrus greening [Candidatus Liberibacter asiaticus (LAS)]. To account for the uncertainty associated with the presence of these diseases, a stochastic budgeting technique was employed in the analysis, incorporating stochastic prices and yields based on discussions with industry experts and researchers. The analysis focused on three possible types of management strategies currently practiced by citrus (Citrus sp.) growers in Florida: 1) production without any specific control activities for citrus canker and citrus greening, 2) canker and greening management without removal or replacement of infected/suspicious trees, and 3) canker and greening management with removal and replacement of infected trees. The analysis was carried out for a 20-year time horizon and average net return per acre and rate of return on investment were considered. The results suggest that despite the presence of disease, it would be profitable to produce tahiti limes in southern Florida. This is because the tahiti lime offers some resistance to both citrus greening and canker and will produce even if minimal attention is paid to controlling the diseases. Of the three management strategies investigated, strategy 2 offers the best prospect in terms of high net returns and highest probability of achieving or surpassing the desired rates of return on investment of 12% per annum. The key finding from the study is that the production of tahiti limes in southern Florida can be profitable if steps are taken to manage the diseases, but contrary to popular view, it might be better to wait until the trees become fully unproductive before disposing of them.