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J.J. Ferguson

The experience and resources of extension specialists can be utilized in resident instruction within a horticultural managers' seminar for advanced undergraduate students, drawing on application of horticultural principles in work situations and other complex issues facing agricultural managers. Guest speakers present an overview of their background, work responsibilities, management philosophy and management practices. Students interact with speakers in this informal seminar and complete written evaluations of speakers and topics for discussion in later classes. This horticultural managers' seminar exposes students to the medley of problems and opportunities facing agricultural managers, utilizes the resources of extension faculty in resident instruction and reinforces ties between commodity departments and their respective industries.

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J.J. Ferguson

The experience and resources of extension specialists can be used in academic teaching programs within a horticultural managers' seminar for advanced undergraduate students, drawing on production, marketing, sales, and distribution managers to discuss application of horticultural principles in work situations and other complex issues facing agricultural managers. Guest speakers present an overview of their background, work responsibilities, management philosophy, and management practices. Students interact with speakers in this informal seminar and complete written evaluations of speakers and topics for discussion in later classes. This horticultural managers' seminar exposes students to the medley of problems and opportunities facing agricultural managers, uses the resources of extension faculty in academic teaching programs, and reinforces ties between commodity departments and their respective industries.

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J.J. Ferguson and F.S. Davies

Young `Hamlin' orange trees [Citrus sinensis (L.) Osbeck] were fertilized six times/year with water-soluble N fertilizer at recommended rates (0.20, 0.34, and 0.38 kg N/tree per year) and with controlled-release fertilizer one time/year [Osmocote, IDBU, and a 44.5% urea-N fertilizer coated with a sulfonated ethylene-propylene-diene polymer (Sherritt, Inc.)] at 0.04, 0.06, and 0.08 kg N/tree per year for years 1, 2, and 3, respectively. There were no differences in trunk diameter, tree height, or tree rating among treatments in any year, although there was a slight reduction in tree rating for some trees with biuret symptoms in the Sherritt treatment in year 2. Leaf nitrogen content was acceptable for all treatments in all 3 years, except for the Osmocote treatment in year 2, which had low to deficient levels. Levels of other nutrients were all within acceptable ranges, except for low potassium levels for the Osmocote in year 2. There were no significant differences in yields of young trees in year 3, the first bearing year. Given its 44.5% N analysis, the total amount of Sherritt controlled-release fertilizer applied to young citrus trees was 4% that of the standard, water-soluble fertilizer and from 39% to 45% that of the two other controlled-release fertilizers in years 1, 2, and 3.

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J. J. Ferguson and C.L. Taylor

Management problems and information needs of Florida's approximately 12,000 citrus growers on 791,290 acres were identified by a statewide citrus management survey. During the summer of 1992, citrus county agents' mailing lists were compiled to create a master list of 2,964 addresses, from which a sample of 833 growers was selected by a stratified proportional sampling procedure. Three hundred ninety-eight useable questionnaires were returned from commercial citrus grove owners and managers in 23 citrus producing counties, representing 307,022 acres, 39% of the current acreage. Survey data on general management, young tree care, pest management, water management and cold protection was further analyzed by whether respondents' groves were bedded or unbedded. Information from this citrus survey and previous ones has been used to develop and evaluate comprehensive statewide citrus extension programs.

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J.J. Ferguson and G.D. Israel

During Summer 1996, a disproportionate systematic sampling procedure was used to obtain an initial sample of 955 citrus growers from the mailing lists of extension agents in 27 counties. Of these, 451 usable responses were returned (67% response rate), providing an expected error of ± 4.3% with a 95% confidence interval. Surveyed growers obtained weather information during the 1995–96 winter from multiple sources, including the National Weather Service (NWS) (48%), commercial radio/TV (48%), Extension offices (18%), private meteorologists (9%), and other sources (10%). After the NWS discontinued agricultural freeze forecasts in Apr. 1996, growers indicated they would rely on commercial radio/TV (72%); private meteorologists (20%), and their County Extension Office (32%) for weather reports. When deciding which cold protection method to use, respondents adopted Extension (35%) and consultants' recommendations (30%), assessed the costs and benefits of cold protection (32%), and assessed risks based on grove history (38%). Cold protection methods used by percent respondents included: flooding groves (22%); grove heaters (2%); wind machines (2%); permanent overhead irrigation systems (2%); ground microsprinklers (76%); in-tree microsprinklers (18%); tree wraps (13%); and tree wraps or covers with microsprinklers (6%). Seventy-three percent of growers reported that their cold protection methods were very effective for a freeze with minimum temperatures of –2°C for at least 4 hr, with 12% and 3% reporting cold protection measures being very effective at –7 and –9°C, respectively.

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J.M. Tarara and J.C. Ferguson

Management strategies like “deficit irrigation” in wine grapes require accurate, reliable information on vine water use, making direct measurements of vine transpiration highly desirable. The heat-balance sap flow method has the advantages of being non-invasive and requiring no other calibration beyond a zero-flow set. Potential violations of the method's assumptions were dealt with and the heat balance method successfully applied to mature grape vines under conditions of extremely high sap flow. Greenhouse studies suggested that vines transpire at night, up to 9.5% of the total 24-h water loss, thus violating the zero-flow assumption for setting the gauge constant. Using a predetermined gauge constant caused smaller errors than using daily, pre-dawn constants set in situ. The steady-state assumption was violated only in early and late hours of the day, and the inclusion of a term to account for the change in heat stored by the stem only marginally improved daily estimates of water use. The assumption of radially uniform temperature across the heated stem segment is violated at very high flows (e.g., >700 g·h–1), but can be corrected for by using wider heaters and adjusting the placement of thermocouples. For a mature, potted vine in the greenhouse, the maximum absolute error in cumulative daytime water use between a sap gauge and a precision load cell was about –10%, with the gauge almost exclusively underestimating water loss. A custom-built, 20-gauge system was run continuously in the field for 90 days. Vine-to-vine variability in water use was not accounted for by normalizing sap flow by leaf area, suggesting that it is critical to include in any field study the largest number of gauges that are technically feasible.

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J.J. Ferguson and G.D. Israel

Although a major freeze has not affected the Florida citrus industry since 1989, growers continue to rank cold protection as an important information need. A moderate freeze during 1996 further emphasized the need to document current cold protection and related management practices. A statewide survey conducted in 1996 indicated that the National Weather Service and commercial radio or television were the primary sources of weather information in 1996, but when asked where they would obtain agricultural weather forecasts after 1996, growers indicated they would rely more on commercial radio or television, private meteorologists and the extension service. Grower awareness of the effectiveness of cold protection methods decreased with temperature and with grower production experience. Microsprinklers were the most commonly used method for both cold protection and irrigation. Fifty percent of growers surveyed used computers for grove management, primarily for financial record keeping, with younger growers more likely to use computers than older growers. The percentage of growers with small groves is decreasing while the percentage of growers with large groves is increasing.

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James J. Ferguson, Elizabeth Lamb and Mickie Swisher

With funding to increase support for organic farming research at land grant universities, organic growers have collaborated with faculty and administrators to develop an undergraduate, interdisciplinary minor at the University of Florida. Required introductory courses focus on general concepts of organic and sustainable farming, alternative cropping systems, production programs, handling, and marketing issues. An advanced horticulture course requires intensive examination of certification procedures, farm plans, soil fertility, and crop management, all of which are integrated into a required field project. Extension faculty have also fostered development of this new curriculum by coordinating regional workshops and field days in collaboration with organic growers and by developing educational materials on organic certification and related issues.

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L. Ferguson, J. Maranto and R. Beede

The effects of four mechanical pruning treatments [hedging, topping, hedging/topping, and hand-pruning (control)] on nut yield, nut quality, alternate bearing, and growth of 14-year-old female `Kerman' pistachio trees on Pistacia atlantica L. rootstocks were assessed. A single pruning was done before an “off,” or low-crop, year followed by retopping of those treatments incorporating topping the first year. Over 7 years, yields of hedged/topped and topped trees were equal to those of control trees, while hedged trees produced significantly less. The incidence of nonsplit shells and blank nuts were not affected by pruning. Nuts weighed more all years for hedged/topped and topped trees than for the others. Alternate-bearing indices within 7 years were lower for pruning treatments incorporating topping. Topping mitigated the fluctuating annual vegetative growth pattern and resulted in 27% of the shoots retaining buds through three successive alternate-bearing cycles after the year of treatment. Hedged/topped and topped trees had significantly less alternation in annual girth growth than control or hedged trees. These results demonstrated that two successive seasons of mechanical topping, started before the off year, produced changes in shoot growth, trunk growth, and bud retention that mitigated alternate bearing through three biennial cycles, without decreasing yield. Thus, severe annual hand-pruning could be used to prevent or minimize alternate bearing of pistachios.

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L. Guazzelli, F.S. Davies and J.J. Ferguson

Two experiments were conducted with containerized `Hamlin' orange trees (Citrus sinensis [L.] Osb.) on `Swingle' citrumelo (C. paradisi Macf. × Poncirus trifoliata [L.] Raf.) rootstock to study the effects of N rate on growth of plants in the nursery. Treatments consisted of the following N rates: 12, 50, 100 and 200 mg·liter-1 applied once a week through drip irrigation. In Expt. 1, fertilization at the 200 mg·liter-1 rate resulted in greater scion growth, trunk diameter and total leaf dry weight as compared to the other rates. In Expt. 2, application of 100 and 200 mg·liter-1 rates resulted in greater scion growth and trunk diameter as compared to lower rates, but no differences were seen between the two highest rates. Trees receiving the 12 and 50 mg·liter-1 rates were stunted and leaves were chlorotic. Therefore, the optimum N rate for trees on `Swingle' citrumelo rootstock is between 100 and 200 mg·liter-1, although the 200 mg·liter-1 rate may not be economically justified. Moreover, the N rate for nursery plants growing on `Swingle' citrumelo rootstock in commercial medium may be higher than for other rootstocks, where rates less than 50 mg·liter-1 produce optimum growth.