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  • Author or Editor: Eric Simonne x
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Several okra (Abelmoschus esculentus) cultivars are now available as alternatives to the standards `Clemson Spineless' (open pollinated) and `Annie Oakley II' (hybrid). Based on the results of four trials involving 20 cultivars, `Mita', `Spike', `Green Best' and `North & South' should be added to the list of recommended cultivars for Alabama and Florida. The experimental `SOK 601' should also be included on that list, but on a for trial basis since it was evaluated only at one location. Other cultivars may perform well at specific locations. Differences among cultivars were also found for ease of harvest. `North & South' and `Baby Bubba' were the easiest and most difficult cultivars to harvest, respectively. The economic feasability of selecting a hybrid cultivar over an open-pollinated one and using plasticulture instead of bare ground was also examined in this study. Using hybrid seeds resulted in an average yield increase per harvest of 92 lb/acre (103 kg·ha-1), which exceeded the estimated 75 lb/acre yield (84 kg·ha-1) increase necessary to offset the additional cost of hybrid seeds. For reasons ranging from improved weed control, increased nutrient and water use efficiency, and double cropping, an increasing interest exists to produce okra with plasticulture, instead of bare ground as done traditionally. The average yield increase per harvest due to plasticulture over bare ground production was 196 lb/acre (220 kg·ha-1). Based on this number, it would take three harvests to produce the 540 lb/acre (605 kg·ha-1) yield increase necessary to offset the additional costs due to plasticulture.

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A TurboPascal computer program was developed to calculate daily water budgets and schedule irrigations. Daily water use (di) is calculated as pan evaporation (Ep) times a crop factor (CFi), where i is crop age. The water balance uses a dynamic rooting depth, the soil water holding capacity (SWC) and rainfall data (Ri). di is added to the cumulative water use (Di-1) and Ri is subtracted from Di. An irrigation in the amount of Di is recommended when Di approximates allowable water use. The program cart be adapted to most crop and soil types, and can be used for on-time irrigation scheduling or for simulating water application using past or projected weather data. This program should increase the acceptance of modem scheduling irrigation techniques by farmers and consultants. Additionally, this program may have application in an overall water management programs for farms, watersheds or other areas where water management is required.

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The effect of irrigation scheduling method (variable crop factor, 1; constant crop factor, 2; empirical, 3), soil water tension (25, 50, 75kPa SWT), tillage (disc arrow, DA, moldboard plow, MP) and planting dates (PD) on total irrigation (TI), number of irrigations (NI), useful (UR) and lost rainfall (LR) was studied using a Pascal program that simulated water budgets of 720 crops of snap bean over 10 years. NI and TI were significantly (p<0.01) lower with met.1. Met.3 had the lowest LR and highest UR, but did not allow the complete calculation of the water balance. TI was significantly higher at 25kPa. MP tillage requested fewer NI and less TI, had lower LR and higher UR. Early PD requested fewer NI and TI, and had higher LR. Hence, when water supply was not limiting and weather data were available, a combination of Met.1, MP at any PD provided a continuous supply of water to the crop while controlling water deficit.

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The Federal Clear Water Act and Florida legislation have mandated the clean-up of impaired water bodies. The BMP manual for vegetable crops lists the cultural practices that could maintain productivity while minimizing environmental impact. BMPs focus on increased fertilizer and irrigation efficiency, but growers must be involved in the demonstration and adoption process if this voluntary program is to be successful. Three commercial vegetable fields from farms recognized as leaders in fertilizer and irrigation management were selected to demonstrate how irrigation and fertilizer management are linked together and how management may prevent water movement below the root zone of melons grown with plasticulture. In Spring 2004, dye (Brilliant blue FCF) was injected into the irrigation water three times during the growing season and soil profiles were dug to determine the depth of dye movement. Similar results were found at all three locations as the dye moved below at an average rate of 1.9 to 3.6 cm per day. Water movement was greater early in the season as irrigation was applied for transplant establishment. These results suggest that some leaching is likely to occur on light-textured soils, even when sophisticated irrigation and fertilization practices are followed. Based on these observations, cooperators spontaneously proposed to use two drip tapes, reduce preplant fertilizer, use a 100% injected N/K program, and/or add organic matter to the soil as attempts to slow water movement below the root zone of their crops. This project shows that growers are more likely to try and adopt sustainable practices when they actively participate in the educational process than when production changes are mandated through legislation.

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Most potato (Solanum tuberosum L.) is produced as a non-irrigated crop in the southeastern United States. This practice makes potato yields dependent on rainfall pattern and amount. An irrigation scheduling method based on a water balance and class A pan evaporation data (Ep) was evaluated in Spring 1996 on a fine sandy loam soil with `LaSoda' potatoes. Planting date was 9 Apr. and standard production practices were followed. The model was (12.7 DAH + 191) * 0.5 ASW = D(DAH-1) + [Ep (0.12 + 0.023 DAH - 0.00019 DAH*DAH) - R(DAH) - I(DAH)], where DAH is days after hilling (DAH = 0 on 14 May), ASW is available soil water (0.13 mm/mm), D is soil water deficit (mm), R is rainfall (mm) and I is irrigation (mm). Root depth expanded at a rate of 13 mm/day to a maximum depth of 305 mm. Root depth at hilling was 191 mm. Controlled levels of water application ranging between 0% and 161% of the model rate were created with drip tapes. The model scheduled irrigations on 35, 39, 43 and 49 DAH. On 85 DAH, potatoes were harvested and graded. Irrigation influenced total yield, marketable yield, and combined US #1 grades (P < 0.01; R 2 > 0.85). Mean marketable yields were 19, 28, and 21 t/ha for the 0%, 100%, and 160% irrigation rates, respectively. These results suggest that supplementing rainfall with irrigation and controlling the amount of water applied by adjusting irrigation to actual weather conditions could increase potato yields. Excessive water, as well as limiting water, reduced potato yields.

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Aquaponics combines the hydroponic production of plants and the aquaculture production of fish into a sustainable agriculture system that uses natural biological cycles to supply nitrogen and minimizes the use of nonrenewable resources, thus providing economic benefits that can increase over time. Several production systems and media exist for producing hydroponic crops (bench bed, nutrient film technique, floating raft, rockwool, perlite, and pine bark). Critical management requirements (water quality maintenance and biofilter nitrification) for aquaculture need to be integrated with the hydroponics to successfully manage intensive aquaponic systems. These systems will be discussed with emphasis on improving sustainability through management and integration of the living components [plants and nitrifying bacteria (Nitrosomonas spp. and Nitrobacter spp.)] and the biofilter system. Sustainable opportunities include biological nitrogen production rates of 80 to 90 g·m−3 per day nitrate nitrogen from trickling biofilters and plant uptake of aquaculture wastewater. This uptake results in improved water and nutrient use efficiency and conservation. Challenges to sustainability center around balancing the aquaponic system environment for the optimum growth of three organisms, maximizing production outputs and minimizing effluent discharges to the environment.

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Most of the winter vegetable production in the southeastern United States is located in Florida. High-value vegetable crops are grown under intensive fertilization and irrigation management practices using drip, overhead, or seepage irrigation systems. Rainfall events may raise the water table in fields irrigated by seepage irrigation resulting in leaching of nutrients when the level is lowered to remove excess water. The objective of this study was to assess the effect of El Niño–Southern Oscillation (ENSO) phases on rainfall distribution and leaching rain occurrences during the fall, winter, and spring tomato (Solanum lycopersicum) growing seasons using long-term weather records available for main producing areas. Differences in fall growing season mean precipitation during El Niño, La Niña, and neutral years were found to be nonsignificant. Winter and spring mean precipitations during El Niño, La Niña, and neutral years were found to be significantly different. Winter and spring average rainfall amounts during La Niña and neutral years were lower than during El Niño years. During El Niño years, at least one leaching rainfall event of 1.0 inch or more in 1 day occurred at all locations and all planting seasons and two of these events occurred in more than 9 of 10 years except during the winter and spring planting seasons at the Tamiami Trail station located in Miami–Dade County. During the fall growing season of El Niño years, three to four 1.0 inch or more in 1-day leaching rainfalls may be expected at least 4 of 5 years at all locations. In the case of larger leaching rainfall events (3.0 inches or more recorded in 3 days or 4.0 inches or more recorded in 7 days), the probability of having at least one event was mostly less than 0.80. Based on these results, nitrogen fertilizer supplemental applications of 30 to 120 lb/acre could be applied during the fall growing season of all ENSO phases and during all planting seasons of El Niño years. Using current fertilizer prices, one supplemental fertilizer application of 30 lb/acre nitrogen and 16.6 lb/acre potassium costs $55/acre. Assuming a median wholesale price of $12 per 25-lb box, this additional cost may be offset by a modest yield increase of 4.6 boxes/acre (compared with a typical 2500 25-lb box/acre marketable yield). These results suggest that ENSO phases could be used to predict supplemental fertilizer needs for tomato, but adjustments to local weather conditions may be needed.

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Measurements of daily, 3-day, and 6-day cumulative pan evaporation using a #2 wash tub or a modified steel drum and a ruler provided an accurate, easy, and inexpensive way to schedule irrigation. Pan factors for these containers, which were covered with a 5-cm-mesh wire under humid climatic conditions, were 1.0 and 1.1, respectively.

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An irrigation scheduling model for turnip (Brassica rapa L.) was validated using a line-source irrigation system in a 2-year field trial. The model used a water balance, a variable root length, and a crop factor function of plant age (i). Evapotranspiration was computed daily as class A pan evaporation times a crop factor [CF(i) = 0.365 + 0.0154i-0.00011i2]. Irrigation according to the model maintained soil water tension at <25 kPa at a 30-cm depth. When rainfall amounts were less than water use, leaf yields responded quadratically to irrigation rates, from 0% to 160% of the model rate, and the highest leaf yield with the lowest water applications corresponded to the model rate. Therefore, this model could replace the “feel or see” methods commonly used for scheduling irrigation of leafy vegetables grown in the southeastern United States.

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Vegetable variety trials are of interest to the entire vegetable industry from breeders, seed companies, growers, consultants, researchers, to Extension personnel. The Auburn Univ. vegetable variety trial results have been made more accessible and user-friendly by becoming available online at http://www.ag.auburn.edu/dept/hf/faculty/esimonne. Users can point and click through a completely searchable database by selecting one of the following categories: 1) explanation of rating system and database, 2) list of vegetable crops, 3) description of variety types of crops, 4) contacting seed companies and web sites, 5) vegetable variety trial team members. For additional information about vegetable variety production, a link to horticulture extension publications has been included. The database gives each vegetable crop tested by Auburn Univ. a rating and allows a search for varieties. For each crop, the five options available to search the database are “rating,” “variety name,” “variety type,” “seed company,” and “type.” The Web page is primarily intended to be a quick, practical reference guide to growers and horticulture professionals in Alabama. Variety performances presented are based on small-scale research plots and test results may vary by location. It is always recommended to perform an on-farm trial of several varieties before making a large planting of a single variety.

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