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Timothy K. Broschat and Kimberly A. Moore

Salvia (Salvia splendens) `Red Vista' or `Purple Vista,' french marigold (Tagetes patula) `Little Hero Orange,' bell pepper (Capsicum annuum) `Better Bell,' impatiens (Impatiens wallerana) `Accent White,' and wax begonia (Begonia ×semperflorens-cultorum) `Cocktail Vodka' were grown in 0.95-L (1-qt) containers using a 5 pine bark: 4 sedge peat: 1 sand substrate (Expts. 1 and 2) or Pro Mix BX (Expt. 2 only). They were fertilized weekly with 50 mL (1.7 fl oz) of a solution containing 100, 200, or 300 mg·L-1 (ppm) of nitrogen derived from 15N-6.5P-12.5K (1N-1P2O5-1K2O ratio) or 21N-3P-11.7K (3N-1P2O5-2K2O ratio) uncoated prills used in the manufacture of controlled-release fertilizers. Plants grown with Pro Mix BX were generally larger and produced more flowers or fruit than those grown with the pine bark mix. With few exceptions, plant color, root and shoot dry weights, and number of flowers or fruit were highly correlated with fertilization rate, but not with prill type. There appears to be little reason for using the more expensive 1-1-1 ratio prills, since they generally did not improve plant quality and may increase phosphorous runoff from bedding plant nurseries.

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J. Pablo Morales-Payan

Dominican oregano is a traditional seasoning leaf in Caribbean cuisine. However, little information is available regarding its mineral nutrition when grown as a commercial crop. Field studies were conducted to determine the short-term response of recently transplanted Dominican oregano to N, P, and K in a clay soil. Dominican oregano plants 15 to 20 cm tall were used. A randomized complete-block design with 13 treatments and three replications was utilized. Treatments were 0 fertilization (control) and 20, 40, 60, and 80 kg/ha of N, P2O5, or K2O applied 20 days after transplanting. Experimental units consisted of 12 plants at with a distancing of 1.0 × 1.0 m. Above-ground biomass accumulation was determined 3 months after treatment. Analysis of variance and regression analysis was performed on the resulting data. Biomass accumulation in Dominican oregano was significantly influenced by N, P, and K fertilization rates. Crop yield increased linearly as nutrient rates increased. Nitrogen fertilization had a stronger influence on Dominican oregano biomass accumulation than P and K fertilization. Results indicate that fertilizing Dominican oregano increases its biomass yield. However, due to its seasoning nature, the effect of mineral fertilization on the essential oils of this crop must be analyzed.

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N. Tremblay and C. Bélec

The necessity of achieving appropriate nitrogen fertilization of vegetable crops relates to both economical and environmental sustainability. Split nitrogen applications have been shown to improve N-use efficiency, in line with the aforementioned objective and should therefore be encouraged. Given the variation in the amount of N naturally provided to, or uptaken by, the crop, strategies are required to tailor supplementary fertilization to actual crop needs, keeping in mind the absolute requirement for optimal yield in quality and quantity. It is suggested that the fertilization rates applied at sowing or later in the season can be figured in two manners. The first relies on modelling; the second on measurements. The modelling (N budget) approach, mostly linked to initiatives on the European continent, would be most applicable to the determination of the first fertilizer dressing. When a plant stand is established, however, canopy-based measurements made either directly or remotely could be developed to make use of the capability of the plants to integrate the properties of the soil environment and to decide upon further top-dressed applications. For this purpose, a fully fertilized “reference plot” has to be introduced in the field in order to overcome the variability induced by season, site and cultivar. With the emergence of “precision farming” and “remote sensing technologies” it is now possible to adjust fertilizer inputs not only at the field level but also within fields based on actual, localized requirements.

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Sandra B. Wilson and Peter J. Stoffella

Peat is used extensively in the nursery industry as a primary component in commercial “soilless” potting media. The increased use of peat as an organic amendment with superior water-holding capacity is challenged by economic and environmental pressures. Developing inexpensive and nutrient-rich organic media alternatives can potentially reduce fertilization rates, irrigation rates, and ultimately, nursery costs. In addition, controversy over the effects of peat mining has inspired a national search for peat substitutes. With our burgeoning population, it is logical to screen waste products as potential alternatives to peat. Growth of Pachystachys lutea Nees. (Golden Shrimp Plant) transplants was evaluated in media containing 0%, 25%, 50%, 75%, or 100% compost derived from biosolids and yard trimmings. Compost was amended with a commercial peat- or coir-based media. As compost composition in the peat or coir-based media increased from 0% to 100%, carbon/nitrogen (C/N) ratios decreased, and media stability, N mobilization, pH, and electrical conductivity (EC) increased. Bulk density, particle density, air-filled porosity, container capacity, and total porosity increased as more compost was added to either peat- or coir-based media. Plants grown in media with high volumes of compost (75 or 100%) had reduced leaf area and reduced shoot and root DW than the controls (no compost). Regardless of percentage of compost composition in either peat or coir-based media, all plants were considered marketable after 8 weeks.

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Monica Ozores-Hampton, Eric Simonne, Eugene McAvoy, Phil Stansly, Sanjay Shukla, Pam Roberts, Fritz Roka, and Tom Obreza

About 10,000 ha of staked tomato are grown each year in the winter–spring season in southwest Florida. Tomatoes are produced with transplants, raised beds, polyethylene mulch, drip or seepage irrigation, and intensive fertilization. With the development of nutrient best management practices (BMPs) for vegetable crops and increased competition among water users, N recommendations must ensure economical yields, but still minimize the environmental impact of tomato production. The current University of Florida–IFAS (UF–IFAS) N fertilization rate of 224 kg·ha-1 (with supplemental fertilizer applications under specified conditions) may require adjustment based on soil type and irrigation system. Because growers should be involved in the development and implementation of BMPs, this project established partnerships with southwest Florida tomato growers. Studies evaluated the effects of N application rates on yield, plant growth, petiole N sap, pests, and diseases. Nine on-farm trials were conducted during the dry winter 2004–05 season. Treatments consisted of N fertilizer rates ranging from 224 to 448 kg·ha-1, with each trial including at least the UF–IFAS rate and the traditional rate. Although total yields were comparable among N rates, there were differences in size category. Nitrogen rates had little effect on tomato biomass 30 and 60 days after transplanting. Changes in petiole sap NO3-N and K concentrations were different between seepage and drip irrigation, but usually above the sufficiency threshold. It is important to consider the type of irrigation when managing tomato and determining optimum N fertilizer rates.

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Yan Chen, Donald Merhaut, and J. Ole Becker

Nitrogen (N) fertilization is critical for successful production of cut flowers in a hydroponic system. In this study, two sunflower cultivars: single-stand `Mezzulah' and multi-stand `Golden Cheer' were grown under two N fertilization rates: 50 mg·L-1 and 100 mg·L-1 in a recirculating hydroponic system. At the same time, `Mezzulah' sunflowers were biologically stressed by exposing each plant to 2000 second-stage juveniles of the plant parasitic nematode Meloidogyne incognita, race 1. The experiment was conducted in May and repeated in Sept. 2004, and plant growth and flower quality between control and nematode-infested plants were compared at the two N rates. The two cultivars responded differently to fertilization treatments. With increasing N rate, the dry weight of `Mezzulah' increased, while that of `Golden Cheer' decreased. Flower size and harvest time were significantly different between the two cultivars. However, N had no effect on flower quality and harvest time. Flower quality rating suggests that quality cut stems can be obtained with 50 mg·L-1 N nutrient solution. Nematode egg count suggests that plants in the nematode treatment were successfully infested with Meloidogyne incognita, however, no significant root galling was observed, and plant growth and flower quality were not affected by nematode infestation.

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Doyle A. Smittle, W. Lamar Dickens, and James R. Stansell

An irrigation scheduling model for snap bean (Phaseolus vulgaris L.) was developed and validated. The irrigation scheduling model is represented by the equation: 12.7(i - 4) × 0.5ASW = Di-1 + [E(0.31 + 0.01i) - P - I]i, where crop age is i; effective root depth is 12.7(i - 4) with a maximum of 400 mm; usable water (cm3·cm-3 of soil) is 0.5 ASW, deficit on the previous day is Di-1; evapotranspiration is pan evaporation (E) times 0.31 + 0.01i; rainfall (mm) is P, and irrigation (mm) is I. The model was validated using a line source irrigation system with irrigation depths ranging from 3% to 145% of tbe model rate in 1985 and from 4% to 180% of the model rate in 1986. Nitrogen fertilization rates ranged from 50% to 150% of the recommended rate both years. Marketable pod yields increased as irrigation rate increased in 1985. Irrigation at 4%, 44%, 65%, 80%, 150%, and 180% of the model rate produced yields that were 4%, 39%, 71%, 85%, 92%, and 55% as great as yields with the model rate in 1986. Marketable pod yields increased as N rate increased when irrigation was applied at 80%, 100%, or 150% of the model rate in 1986, but pod yields varied less with N rate when irrigation was applied at 4%, 44%, 65%, or 180% of the model.

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San-Gwang Hwang, Hsiao-Chien Chao, and Huey-Ling Lin

Global surface temperatures are predicted to increase by 1 to 4 °C by the year 2100. To unravel the risks from rising temperature to Taiwan’s summer leafy vegetable production, the phenotypical and physiological responses of two leafy crops, pak choi (Brassica chinensis L. cv. Quanzhou) and edible amaranth (Amaranthus tricolor L. cv. White leaf), were compared under an elevated temperature. A temperature increase from 28 to 32 °C resulted in lower leaf calcium, magnesium, and manganese concentrations (dry weight basis) in pak choi without significant changes in shoot dry weight, suggesting potential negative effects of the elevated temperature on pak choi leaf nutrient status. However, increased temperature promoted both root and leaf growth in edible amaranth, which may be beneficial to its yield, making edible amaranth a potential summer leafy vegetable crop for Taiwan. Furthermore, a temperature change from 28 to 32 °C resulted in a higher leaf nitrate concentration in edible amaranth, because of the lower nitrate reductase activity (NRA). Thus, suitable nitrogen fertilization rates and programs under elevated temperature conditions should be reconsidered in the future. To sum up, a future rise in summer temperatures may impose negative impacts on pak choi leaf nutrient status but positive impacts on edible amaranth production.

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Joseph P. Albano, Donald J. Merhaut, Eugene K. Blythe, and Julie P. Newman

Nutrient release characteristics of four different controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were monitored during an 11-month period in a simulated outdoor nursery production facility. Although no plants were used in the experiment, fertilization rates, irrigation regimes, and cultural practices simulated those typically used to produce fast-growing, high-nutrient-requiring containerized woody ornamentals. Fertilizer prill release characteristics were monitored through analyses of leachates, which were collected weekly. Concentrations of Mg, Mn, Zn, Cu, and Mo were relatively high during the first 5 to 10 weeks of the experiment, then declined and usually stabilized during the remainder of the study. However, Mn and Zn displayed erratic increases in concentrations several times throughout the study. Calcium concentrations did not increase until the fifth week, rapidly peaked to about 300 mg·L–1, and then decreased and leveled off to ≈80 to 100 mg·L–1 during the remainder of the study. Several significant differences were observed between treatments. The Osmocote treatment had significantly greater Ca and Mg concentrations in the leachate than the other fertilizer types during the last 6 weeks of the study, whereas the Nutricote treatment often had significantly greater Fe concentrations than leachates from other treatments, especially during the last 26 to 35 weeks of the study, and significantly greater Zn concentrations than the other CRFs during the last 21 weeks of the study. Based upon U.S. Environmental Protection Agency guidelines, concentrations of Fe were often more than the allowable limit of 0.3 mg·L–1 with all fertilizer types, but especially with Nutricote. Concentrations of Mn and Cu also exceeded federal guidelines, particularly during the first several weeks of the study.

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Carmen Feller and Matthias Fink

The nitrogen requirement of broccoli (Brassica oleracea var. italica) ranges from 300 to 465 kg·ha–1. Recommendations for N fertilization are accordingly high. High fertilizer rates applied at planting result in a high soil mineral N content that remains high for weeks because the N requirement of the crop is low at early growth stages. Therefore, the risk of leaching is high for several weeks until the available N is finally taken up by the crop. Our study had two objectives: 1) to quantify yield responses to preplant fertilization, and 2) to test our hypothesis that the preplant fertilization rate could be reduced without yield losses by increasing the N content in the transplants and improving crop establishment. Field experiments were carried out on transplants with four levels of N content in dry matter (0.018 to 0.038 g·g–1 dry weight), which were tested in all combinations with four fertilization timings. All treatments received the same amount of N fertilizer (270 and 272 kg·ha–1 in 2001 and 2002, respectively), but with different rates of supply at the time of planting (0 to 90 kg·ha–1 N fertilizer plus 30 and 28 kg·ha–1 soil mineral N in 2001 and 2002, respectively). Total and marketable yields increased significantly with an increasing N supply at time of planting. In our experiments, in which topdressing was applied 25 days after planting, an N supply at planting of 80 to 118 kg·ha–1 was required to obtain maximum marketable yields. The N content in transplants had little effect on growth and yield, and there were no significant interactions between the N content in the transplant and fertilizer timing.