Progress 12/01/87 to 09/30/30
Outputs
This project is terminated due to the closure of the University of Florida, IFAS, Hastings REC.
Impacts
None to report
Publications
- No publications reported this period
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Progress 10/01/99 to 09/30/00
Outputs
Several preliminary studies have been started to evaluate potato production best management practices including (a) modeling the nutrient uptake, dry matter accumulation, and bulking of Atlantic potatoes under short day growth conditions. The bulking of this variety is less under short than long day production regimes; (b) evaluation of controlled release fertilizers in potato production. Controlled release fertilizers were more efficient at supplying nitrogen to a potato crop producing similar production values at lower nitrogen rates than conventional fertilizer sources; and (c) the utility of drip irrigation on fertilizer management and water use was demonstrated. Fertigation practices produced similar potato yields at 1/3 the water usage and 3/4 the nitrogen rate as compared to conventional seepage-irrigation production practices. The second area of non-projected research is the evaluation of herbicides for crop production. Herbicide trials were conducted in
potato and cabbage to identify more effective compounds that are less harmful to the crop and the environment.
Impacts
Lower application rates of nitrogen reduce threat of nitrogen run-off in north Florida watersheds.
Publications
- No publications reported this period
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Progress 10/01/97 to 09/30/98
Outputs
Inactive
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 10/01/96 to 09/30/97
Outputs
Efficacy of fungicides for control of potato late blight caused by Phytophthora infestans, US-8 was compared in seven field experiments. All fungicide applications were made after initial infection. Generally, standard protectant fungicides (Chlorothalonil, mancozeb, maneb, and metiram + fentin hydroxide) were equally effective as the new chemicals (i.e. fluazinam, cymoxanil + mancozeb, propamocarb HCL + chlorothalonil, and ditmethomorph + mancozeb) which were evaluated. None of the fungicides exhibited curative activity. Disease conditions were intense during the first month after emergence but were tempered by dry, hot weather after mid season. Samples of late blight from both tomato and potato were analyzed for presence of different strains of P. infestans. Five different allozyme phenotypes (US-1, US-8, US-17, US-7, and US-?) were detected during 1997 in samples from south Florida. In south Florida, US-17 predominated, particularly in tomatoes, whereas only US-8
was found in north Florida potatoes. Both A1 (US-1, US-17, and US-?) and A2 (US-7, US-8) mating types were found in Florida during 1997. There was no evidence, however, of sexual reproduction of the pathogen in field samples.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 10/01/95 to 09/30/96
Outputs
Yields of 35.2 and 35.3 mt/ha and total seasonal irrigation applications of 648 cm and 254 cm water were, respectively, associated with the seep and drip irrigation system in 1996. Additional work is in progress to evaluate soil hydraulic properties and run-off characteristics of the site to aid in modeling surface water run-off. Sixty fungicide treatments which included several products containing cymoxanil, propamocarb HCL, and dimethomorph in combination with other fungicides, were evaluated for control of new genotypes of the late blight pathogen (Phytophthora infestans) in Atlantic and Red LaSoda potatoes. Generally, all traditional preventative fungicides provided late blight control equal to that of the new products. Percentages disease control observed in selected treatments were: mancozeb 99-100%, metiram 79-99%, metiram 80-99%, metiram + fentin hydroxide 70-100%, chlorothalonil 79-99%, cymoxanil + mancozeb, propamocarb HCL + chlorothalonil, and dimethomorph
+ mancozeb mixtures, respectively, 88-99%, 90-100%, and 82-99%. Weather conditions were only moderately favorable for late blight development and % disease in the controls varied from 23 to 76%.
Impacts
(N/A)
Publications
- NO PUBLICATIONS REPORTED THIS PERIOD.
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Progress 10/01/94 to 09/30/95
Outputs
A field scale experiment was designed to evaluate conventional seepage irrigation system compared to subsurface drip tubing using potatoes as a test crop. The plots were 182 m long and 18 m wide plus buffers of equal width. Conventional seepage had open water furrows spaced 18 m apart with 16 rows of potatoes in between. The microirrigation tubing laterals were spaced 6 m apart and were chiseled into the soil 0.5 m below surface. Emitters were spaced in the tubing every 1.2 m and provided 3.78 l hr-1. Water was independently supplied to each plot by using float-actuated microswitches. Daily records were taken for water used, water table levels, number of pump cycles, along with weather records. The microtubing provided adequate water to the crop and used approximately 33% less water than the seepage method. Yields averaged 26.5 Mg ha-1 for conventional and 24.6 Mg ha-1 for microtubing. The difference was not significant. The seepage system normally cycled once or twice
per day. The average was 9.71 hrs per cycle. It cycled more in the earlier part of the season. A typical day in the later season was on at mid morning and off at 8 to 10 PM. The drip system averaged 2.01 hrs per cycle since the water table with this system recovered faster. Little or no runoff occurred with the drip system while the seepage system had nearly continuous runoff. The energy requirement to supply a unit of water was much higher on the drip system since higher pressure (270 Pa) was used. For the entire season, 222 kwh.
Impacts
(N/A)
Publications
- NO PUBLICATIONS REPORTED THIS PERIOD.
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Progress 10/01/93 to 09/30/94
Outputs
Significant changes in U.S. populations of the potato late blight pathogen, Phytophthora infestans (PI) have been reported since 1987. Reports of new genotypes, the A-2 mating type (MT), and resistance (MR) to the systemic fungicide metalaxyl have come from several regions of north America, including some which ship seed tubers to Florida. Late blight samples and PI isolates were collected from Florida potato fields and sent to S. B. Goodwin, Cornell Univ., K. L. Deahl and R. W. Goth, USDA Beltsville, and T. Young, Ciba Corp, Vero Beach, FL. Florida PI isolates during 1993 and 1994 included the new genotypes (Sensu Goodwin el.al.) US 6 (MT A-1; MR), US 7 (MT A-2; MR), and US 8 (MT A2; MR). Effective fungicides for controlling the MR US 8 genotype included: maneb, metiram, mancozeb, and chlorothalonil; and the combinations of metalaxyl + mancozeb alternated with mancozeb, metalaxyl + chlorothalonil alternated with chlorothalonil, Fostyl-Al + potassium carbonate + either
maneb or mancozeb, and maneb + fentin hydroxide.
Impacts
(N/A)
Publications
- NO PUBLICATIONS REPORTED THIS PERIOD.
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