North Florida Research and Education Center

155 Research Road
Quincy, FL 32351-5677
Phone: (850) 875-7116
Fax: (850) 875-7188
Email: hoch@ufl.edu

Publications

George Hochmuth

Center Director, Extension Specialist, Vegetables
Professor of Horticultural Sciences

Maynard, D.N., and G.J. Hochmuth. 1997. Knotts' Handbook for Vegetable Growers, 4th ed. Wiley Interscience, J. Wiley and Sons, NY.

Hochmuth, G.J., E. Kee, T.K. Hartz, F.J. Dainello, and J. E. Motes, 2001.  Cultural Mangement. IN: D.N. Maynard (ed). Watermelons:Characteristics, Production and Marketing. ASHS Horticultural Crop Production Series. ASHS Press. Alexandria, Va

Gunders, K., S.A. Sargent, S.G. Jacob, G.J. Hochmuth, and D.J. Cantiliffe. 2002. Restructuring State Major Programs to Address Performance-based Budgeting and Issues Programming.  Florida Agric. Exp. Sta. Journal Series No. R-08472. HortTechnology July-September 2002 12(3):492-495

Hochmuth, G. J. and D.N. Maynard. 2002.  Generating Private-Sector Funding for Extension Programs.  Florida Agric. Exp. Sta. Journal Series No. R-08089.  HortTechnology July-September 2002 12(3):495-498

Hochmuth, G., P. Weingartner, C. Hutchinson, A. Tilton, and D. Jesseman. 2002. Potato Yield and Tuber Quality Did Not Respond to Phosphorus Fertilization of Soils Testing High in Phosphorus Content.  Florida Agric. Exp. Sta. Journal Series No. R-08117. HortTechnolgy July-September 2002 12(2):420-423

Locascio, S.J. and G. J. Hochmuth. 2002. Watermelon Production as Influenced by Lime, Gypsum, and Potassium.  Florida Agric. Exp. Sta. Journal Series No. R-08091. HortScience, Vol. 37(2):322-324.

Arenas, M., C.S. Vavrina, J.A. Cornell, E.A. Hanlon, and G.J. Hochmuth. 2002. Coir as an Alternative to Peat in Media for Tomato Transplant Production.  HortScience, Vol. 37(2):309-312

Hochmuth, G.J. 2000. Management of Nutrients in Vegetable Production Systems in Florida.  Florida Agric. Exp. Sta. Journal Series No. N-01877. Soil Crop Sci. Soc. Florida Proc. 59:11-13

Hochmuth, G.J., E.A. Hanlon, and G. Kidder. 2000.  Appropriate Uses of Soil Fertility Testing and the UF-IFAS Standardized Fertilization Recommendation System: A Position Paper from the UF-IFAS Plant Nutrient Oversight Committee.  Florida Agric. Exp. Sta. Journal Series No. N-01948. Proc. Fla. State. Hort. Soc. 113:2000 pp138-140

Smith, C., G. Hochmuth, and G. Jones. 2000.  Cucumber Responses to Soil Mg and to Mg Fertilization Were Unpredictable.  Florida Agric. Exp. Sta. Journal Series No. N-01947. Proc. Fla. State Hort. Soc. 113:2000. pp261-265

Carrijo, O.A., and G. Hochmuth. 2000.  Tomato Responses to Preplant-incorporated or Fertigated Phosphorus on Soils Varying in Mehlich-1 Extractable Phosphorus.  Florida Agric. Exp. Sta. Journal Series No. R-06393.  HortScience, Vol. 35(1):67-72.

Hochmuth, G., O. Carrijo, and K. Shuler. 1999.  Tomato Yield and Fruit Size Did Not Respond to P Fertilization of a Sandy Soil Testing very High in Mehlich-1 P.  Florida Agric. Exp. Sta. Journal Series No. 6421.  HortScience, Vol. 34(4):653-656.

Hochmuth, G.J., J.K. Brcht, and M.J. Bassett. 1999. Nitrogen Fertilization to Maximize Carrot Yield and Quality on a Sandy Soil.  Florida Agric. Exp. Sta. Journal Series No. R-06388.  HortScience, Vol. 34(4):641-645.

Hochmuth, R., L.L. Leon, T. Crocker, D. Dinkins, and G. Hochmuth. 1998.  Evaluation of Two Soilless Growing Media and Three Fertilizer Programs in Outdoor Bag Culture for Strawberry in North Florida.  Florida Agric. Exp. Sta. Journal Series No. N-01681. Proc. Fla. State Hort. Soc. 111:1998. pp341-344.

Hochmuth, R., L.L. Leon, and G.J. Hochmuth. 1998.  Evaluation of Several Cultivars of Cluster Tomatoes for Florida Hydroponic Greenhouse Growers.  Florida Agric. Exp. Sta. Journal Series No. N-01682. Proc. Fla. State Hort. Soc. 111:1998.  pp70-72

Waldo, E.A., G.J. Hochmuth, and D.J. Cantliffe.  1998.  Growing 'Galia' Muskmelons Using Walk-in Tunnels and a Soilless Culture System in Florida and the Economic Feasibility of Using These Systems.  Florida Agric. Exp. Sta. Journal Series No. N-01709. Proc. Fla. State Hort. Soc. 111:1998.  pp62-69.

Vavrina, C.S., G.J. Hochmuth, J.A. Cornell, and S.M. Olson. 1998. Nitrogen Fertilization of Florida-grown Tomato Transplants: Seasonal Variation in Greenhouse and Field Performance.  HortScience 33(2):251-254.

Willcutts, John F., Allen R. Overman, George J. Hochmuth, Daniel J. Cantliffe, and Puffy Soundy. 1998. A Comparison of Three Mathematical Models of Response to Applied Nitrogen: A Case Study Using Lettuce. HortScience 33(5):833-836.

Locascio, S.J., G.J. Hochmuth, S.M. Olson, R.C. Hochmuth, A.A. Csizinszky, and K.D. Shuler. 1997. Potassium Source and Rate for Polyethylene-mulched Tomatoes. HortScience 32(7):1204-1207.

Locascio, Salvadore J., George J. Hochmuth, Fred M. Rhoads, Steve M. Olson, Alan G. Smajstrla, and Ed A. Hanlon. 1997. Nitrogen and Potassium Application Scheduling Effects on Drip-irrigated Tomato Yield and Leaf Tissue Analysis. HortScience 32(2):230-235.

Hochmuth, George J., Earl E. Albregts, Craig C. Chandler, John Cornell and Jay Harrison. 1996. Nitrogen Fertigation Requirements of Drip-irrigated Strawberries. J. Amer. Soc. Hort. Sci. 121(4):660-665.

Albregts, Earl E., George J. Hochmuth, Craig K. Chandler, John Cornell, and Jay Harrison. 1996. Potassium Fertigation Requirements of Drip-irrigated Strawberry. J. Amer. Soc. Hort. Sci. 121(1):164-168.

Olson, Stephen M., George J. Hochmuth, and Robert C. Hochmuth. 1994. Effect of Transplanting on Earliness and Total Yield of Watermelon. HortTechnology Vol. 4(2):141-143.

Hochmuth, G.J. 1994. Efficiency Ranges for Nitrate-Nitrogen and Potassium for Vegetable Petiole Sap Quick Tests. HortTechnology, 4(3):218-222.

Hochmuth, George. 1994. Current Status of Drip Irrigation for Vegetables in the Southeastern and Mid-Atlantic United States. HortTechnology 4(4):390-393.

Hochmuth, Bob, and George Hochmuth. 1994. Responses of Pepper and Watermelon to Paper and Polyethylene Mulches in Two Spring Seasons in North Florida. Proc. Fla. State Hort. Soc. 107:102-105.

Hochmuth, George, Ken Shuler, Ed Hanlon, and Nancy Roe. 1994. Pepper Response to Fertilization with Soluble and Controlled-Release Potassium Fertilizers. Proc. Fla. Sate Hort. Soc. 107:132-139.

Hochmuth, Robert C., George J. Hochmuth, and Michael E. Donley. 1993. Responses of Cabbage Yields, Head Quality, and Leaf Nutrient Status, and of Second-Crop Squash, to Poultry Manure Fertilization. Soil Crop Sci. Soc. Florida Proc. 52:126-130.

Hochmuth, G., E. Hanlon, B. Hochmuth, G. Kidder, and D. Hensel. 1993. Field Fertility Research with P and K for Vegetables - Interpretations and Recommendations. Soil Crop Sci. Soc. Florida Proc. 52:95-101.

Hochmuth, G., W. Stall, and R. Hopper. 1993. Certain Pesticides Can Lead to Premature Degradation of Polyethylene Mulch in the Field. Plasticulture. pp.35-40.

Hochmuth, G.J., S.J. Locascio, T.E. Crocker, C.D. Stanley, G.A, Clark, and L.R. Parsons. 1993. Impact of Microirrigation on Florida Horticulture. HortTechnology. 3(2):223-229.

Hochmuth, G., E. Hanlon, G. Kidder, D. Hensel, W. Tilton, J. Dilbeck, D. Schrader. 1993. Fertilization Demonstrations for the Tri-County Potato Production Area of Northeast Florida. Proc. Fla. State Hort. Soc. 106:190-198.

Hochmuth, George J., Ed A. Hanlon, and John Cornell. 1993. Watermelon Phosphorus Requirements in Soils with Low Mehlich-I-extractable Phosphorus. HortScience 28(6):630-632.

Hochmuth, George J., Salvadore J. Locascio, Stephen R. Kostewicz, and Frank G. Martin. 1993. Irrigation Method and Rowcover Use for Strawberry Freeze Protection. J. Amer. Soc. Hort. Sci. 118(5):575-579.

Hochmuth, G.J., R.C. Hochmuth, M.E. Donley, E.A. Hanlon. 1993. Eggplant Yield in Response to Potassium Fertilization on Sandy Soil. HortScience 28(10):1002-1005.

Hochmuth, George J. 1992. Concepts and Practices for Improving Nitrogen Management for Vegetables.   HortTechnology 2(1):121-125.

Hochmuth, G.J. 1992. Fertilizer Management for Drip-irrigated Vegetables in Florida.  HortTechnology 2(1):27-32.

Hanlon, E.A., and G.J. Hochmuth. 1992. Recent Changes in Phosphorus and Potassium Fertilizer Recommendations for Tomato, Pepper, Muskmelon, Watermelon, and Snapbean in Florida. Commun. Soil Sci. Plant Anal. 23:(17-20) pp. 2651-2665.

Hanlon, E.A., G.J. Hochmuth, and O.A. Diaz. 1991. Mehlich-I Soil-test Calibration for Watermelon: Cu, Zn, and Mn. Commun. Soil Sci. Plant Anal. 22: (19&20) pp.2077-2087.

Hochmuth, R.C., and G.J. Hochmuth. 1991. Nitrogen Requirement for Mulched Slicing Cucumbers. Soil and Crop Sci. Soc. Fla. Proc. 50:130-133.

Clark, G.A., C.D. Stanley, D.N. Maynard, G.J. Hochmuth, E.A. Hanlon, D.Z. Haman. 1991. Water and Fertilizer Management of Microirrigated Fresh Market Tomatoes. Transactions of the ASAE. Vol. 34, No. 2, pp. 429-435.

Hochmuth, G.J., E.A. Hanlon, P.R. Gilreath, and K.D. Shuler. 1990. Effects of K Rates on Yield of Tomato at Three Commercial Production Sites. Soil and Crop Sci. Soc. Fla. Proc. 50:169-172.

Hochmuth, Robert C., Steve. M. Olson, George J. Hochmuth. 1990. Short Day Onion Cultivars for North Florida. Proc. Fla. Sate Hort. Soc. 103:96-98.

Hochmuth, G.J., D.J. Cantliffe, C. Meline. 1990. Mulching and Planting Methods Affect Performance of Sweet Corn in Florida. Proc. Fla. State Hort. Soc. 103:91-93.

Rhoads, F.M., E.A. Hanlon, Jr., S.M. Olson, and G.J. Hochmuth. 1990. Response of Snap Beans to N-Rates and Soil-Test P and K. Soil and Crop Sci. Soc. Fla. Proc. 49:10-13.

Extension Publications (Research Publications)

Hochmuth, George. 1996. Commercial Vegetable Fertilization Guide. Fla. Coop. Ext. Serv. Cir 225D.

Hochmuth, George, Ed Hanlon, George Snyder, Russell Nagata, and Tom Schueneman. 1996. Fertilization of Sweet Corn, Celery, Romaine, Escarole, Endive, and Radish on Organic Soils in Florida. Fla. Coop. Ext. Serv. Bul 313.

Hochmuth, George. Fertilization of Pepper in Florida. 1996. Fla. Coop. Ext. Serv. Cir 1168.

Hochmuth, George J., and Edward A. Hanlon. 1995. IFAS Standardized Fertilization Recommendations for Vegetable Crops. Fla. Coop. Ext. Serv. Cir 1152.

Hochmuth, George. Plant Petiole Sap-Testing. 1994. Fla. Coop. Ext. Serv. Cir 1144.

Hochmuth, George, Don Maynard, Charles Vavrina, and Ed Hanlon. 1991. Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida. Fla. Coop. Ext. Serv. SSVEC 42.

Hochmuth, George J., and Gary A. Clark. 1991. Fertilizer Application and Management for Micro (or Drip) Irrigated Vegetables in Florida.  Fla. Coop. Ext. Serv. SSVEC 45.

Hochmuth, G.J. (ed.). 1991. Greenhouse Vegetable Production Guide. SP48 Vol. III, 98 pp.

Hochmuth, George. 1990. Nutrient Solution Formulation for Hydroponic (Rockwool and NFT) Tomatoes in Florida. Fla. Coop. Ext. Serv. SSVEC 44.

Hochmuth, George. 1990. Design Suggestions and Greenhouse Management for Rockwool Vegetable Greenhouses in Florida. Fla. Coop. Ext. Serv. SSVEC 41.

Hochmuth, George, (ed.). 1990. Nitrogen Management in Vegetable Production for Groundwater and Health Protection. Fla. Coop. Ext. Serv. SSVEC 940.

Hochmuth, G.J., D.N. Maynard, and S.P. Kovach. 1988. Selection of an Irrigation System for Vegetable Crop Production in Florida. Fla. Coop. Ext. Serv. Cir 784.

Hochmuth, George. 1988. Polyethylene Mulching for Early Vegetable Production in North Florida. Fla. Coop. Ext. Serv. Cir 805.

Hochmuth, George, Steve Kostewicz, and William Stall. 1987. Row Covers for Commercial Vegetable Culture in Florida. Fla. Coop. Ext. Serv. Cir 728.

Abstracts:

Restructuring State Major Programs to Address Performance-based Budgeting and Issues Programming - To remain competitive for federal and state funding, state cooperative extension services must proactively incorporate issues programming and performance-based budgeting.  State major program (SMP) design teams, which provide linkages between clientele groups and the research base, must conduct needs assessments to adjust to this new atmosphere of accountability.  A case study illustrates how one Florida SMP (FL107, vegetable production, harvest, handling, and integrated pest management in Florida) restructured its design team to become more flexible and proactive to target a wider range of outcomes.  While still in the implementation phase, this model has already resulted in improved communication within the organization, better addressing extension needs at county level while facilitating reporting at the state level.

Generating Private-Sector Funding for Extension Programs - Delivery of modern extension programs involves considerable expenses that are becoming scarce from traditional sources.  Successful extension educational programs will need to find additional revenue sources to fund educational materials, speaker costs, conferences, and other needs.  It is important to become as financially efficient as possible and sometimes this means consolidating some programs and eliminating others.  Charging fees to attendees is one means of covering costs of delivering programs.  The University of Florida is partnering with the agriculture industry and trade journal publishers to provide resources and publishing for educational programs and materials.

Potato Yield and Tuber Quality Did Not Respond to Phosphorus Fertilization of Soils Testing High in Phosphorus Content - Phosphorus (P) fertilization studies were conducted on four commercial farms and at the University of Florida Institute of Food and Agricultural Sciences Hastings Research and Education Center in Hastings.  All sites were in the potato (Solannum tuberosum production area of northeast Florida.  Preplant Mehlich-1 soil test P was very low at one commercial site and very high at the other four sites.  The yield of marketable size A tubers, the desired tuber category, did not respond to P fertilization from 0 to 66 lbs/acre (74.0 kb·ha^-1) of P at any site.  The average yield across all sites was 324 cwt/acre [16.2 ton/acre (36.3 t·ha^-1)].  Leaf-P concentration at midseason did not respond to P fertilization.  Leaf-P concentration average 0.38%, which was sufficient for potato.  Potato tuber specific gravity averaged 1.075 and responded slightly to P fertilization only at one site.

Watermelon Production as Influenced by Lime, Gypsum, and Potassium - Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] were grown with three rates each of lime, gypsum, and K during two season to evaluate their effects on fruit production and mineral concentration.  The first experimental site was a recently cleared Sparr fine sand with an initial water pH of 5.0 and Mehlich-1 extractable K of 8 mg·kg^-1 (very low) and 20 mg·kg^-1 Ca (very low).  The second site was a virgin Pomona fine sand with a water pH of 2.8, 29 mg·kg^-1 K (low), and 612 mg·kg^-1 Ca (high).  'Crimson Sweet' fruit yields were reduced 10% with an increase in lime rate from 0 to 4.48 t·ha^-1 in the first season.  In the second season, lime rate had no effect on yield.  In both season, fruit yields were reduced 14% with an increase in Ca from gypsum from 0 to 1.12 t·ha^-1.  On the soil testing very low in K, yield increased with an increase in K rate from 90 to 225 kg·ha^-1 with no lime or gypsum. On the soil testing low in K, greatest yields were obtained with 90 kg·ha^-1 K with no lime and gypsum.  Application of lime and gypsum increased Ca and deceased K in seedlings but not consistently in older leaf and fruit tissues.  An increase in K application increased leaf K in the first season but not in the second.  Fruit firmness and soluble solids content were not consistently affected by treatment during the two seasons.  Thus, on soils low in toxic elements (Mn and Al) such as used in this study, watermelon will grow well and tolerate a wide range of soil pH values without additional Ca from lime or gypsum.

Coir as an Alternative to Peat in Media for Tomato Transplant Production - Sixteen media prepared from peat, coir, vermiculite, or perlite were used to determine the optimum growing media from tomato (Lycopersicum esculentum Mill.) transplants.  Medium composition did not affect tomato seed emergence, although seedling emergence was higher in winter (90%) than summer (85%).  Greatest transplant rood dry weight, stem diameter, and leaf area were achieved in 50% to 75% peat + 25% to 50% vermiculite in summer.  In winter, greatest transplant rood dry weight, stem diameter, and leaf area were achieved in eight media: 100% peat, 75% peat + 25% vermiculite, 75% peat + 25% perlite, 50% peat + 50% vermiculite, 50% peat + 50% perlite, 25% peat + 50% coir + 25% vermiculite, 50% peat + 25% coir + 25% vermiculite, and 25% peat + 25% coir + 25% vermiculite + 25% perlite.  Transplants grown with >50% coir exhibited reduced plant growth compared to peat-grown transplants, a response that may be associated with high N immobilization by microorganism and high C:N ratio.  Despite transplant growth differences during the summer, fruit yields generally were unaffected by transplant media.

Management of Nutrients in Vegetable Production Systems in Florida - Vegetables are produced on nearly 300,000 acres (120,000 ha) in Florida and fertilization is important for profitable production of high-quality vegetables in this state.  Optimum management of nutrients for vegetable production is important for several reasons.  First of all, fertilization represents a significant input cost for vegetable producers, for some crops amounting to 8 to 10% of total costs of production.  Secondly, nutrients, such as N or K can be mobile in the sandy soils of Florida and this is a particular problem under heavy rainfall or excessive irrigation.  Finally, nutrient management is important because nutrients lost to the environment can negatively impact the quality of ground or surface waters.  Vegetable growers have several technologies within their reach to maximize nutrient management, including calibrated soil testing, polyethylene mulch, fertigation, controlled-release fertilizers, and plant tissue testing, among others.  In addition to these technologies pertaining directly to nutrient management, growers have new information on optimum irrigation management at the farm level.  Water management on the farm is critical to successful nutrient management.

Appropriate Uses of Soil Fertility Testing and the UF-IFAS Standardized Fertilization Recommendation System: A Position Paper from the UF-IFAS Plant Nutrient Oversight Committee - The UF-IFAS Standardized Fertilization Recommendation System (SFRS) is the resource of fertilization recommendations for commercial crops and homeowner situations.  It was developed to advise individuals on liming and fertilization practices.  Working Groups appointed by the Chair (UF-IFAS Dean for Extension) of the UF-IFAS Plant Nutrient Over-sight Committee review fertilization research and prepare papers summarizing the research and indicating areas of need for more research.  Modifications in the IF-IFAS fertilization recommendations are recommended to the Committee.  The UF-IFAS SFRS has not been proposed or calibrated for use to determine fertilizer management for environmental regulatory purposes.  This paper summarizes the history of the UF-IFAS SFRS, describes the process in use for developing and instituting fertilization recommendations, and documents the UF-IFAS position on the appropriate use of soil testing.

Cucumber Responses to Soil MG and to Mg Fertilization Were Unpredictable - The Mehlich-1 Mg soil test calibration and Mg fertilizer requirements were evaluated for cucumber grown on sandy soil.  The experiment was conducted on a soil initially testing low in Mg (<20 mg·kg^-1 Mg).  Soil samples were taken from the beds of each plot prior to Mg treatment application each season.  Magnesium fertilizer for all treatments was incorporated into the soil before mulching.  In spring 1997, treatments were  0, 17, 34, 67, and 134 kg·ha^-1 Mg.  For fall 1997, each spring treatment plot was split into four plots, each receiving either 0, 17, 34, 67, and 134 kg·ha^-1 Mg.  For spring 1998, each of the fall 1997 plots was split into six plots, each receiving either 0, 11, 22, 34, 45, or 90 kg·ha^-1 Mg.  Plants were grown on raised beds that were fumigated with methyl bromide and mulched with polyethylene.  'Lightning' cucumber seeds were planted, and the crop was irrigated by drip irrigation using water that was softened with a household water softener to remove Mg.  Harvested fruits were graded as marketable or cull, according to USDA standards.  For spring 1997, Mg fertilizer treatments did not affect marketable yield, although yield was significantly affected by the initial Mg soil test index.  In fall 1997, yield was improved by the first increment of Mg fertilizer, but the initial soil test index did not affect yield.  In spring 1998, yield was not affected by Mg fertilizer treatments, but was affected by initial soil test index.  Leaf Mg concentration at first bloom was not affected by Mg fertilizer treatment and was adequate.  Leaf Mg concentration at harvest increased linearly with Mg fertilization in two out of three season.  Fertilization with recommended rate of Mg resulted in leaf Mg concentrations in the adequate range.  The inconsistent and unpredictable responses to Mg reflected the mobility of this element in sandy soils or that the native soil concentration of Mg was already near the critical level in the crop season.  Under any soil test Mg situation in this study, the recommended amount of Mg was adequate fro greatest yield.

Tomato Responses to Preplant-incorporated or Fertigated Phosphorus on Soils Varying in Mehlich-1 Extractable Phosphorus - Experiments were conducted to evaluate the yield response of tomato (Lycopersicon esculentum Mill.) to P, either preplant-incorporated or injected through the drip irrigation system, on soils with low, high, or very high soil P content.  Fertilization through drip irrigation system (fertigation) was more efficient than preplant incorporation of P fro soil that tested low in P (9 mg·kg^-1 Mehlich-1 P).  On soil testing low in P, marketable yield response to preplant soil P application rates (0 to 100  kg·ha^-1 ) was maximum at 61 kg·ha^-1 P according to the linear-plateau model, but 37 kg·ha^-1 P according to the quadratic-plateau model.  The lower value is about one-half the P recommended by Univ. of Florida for low P soils.  On soil testing high in P (48 mg·kg^-1 Mehlich-1 P) the linear-plateau model predicted a maximum yield of 72.8 t·ha^-1 with 25 kg·ha^-1 P.  The Univ. of Florida recommended no P for that soil.  On soil testing very high in P (85 mg·kg^-1 Mehlich-1 P), there was no yield improvement with P fertilization.

Tomato Yield and Fruit Size Did Not Respond to P Fertilization of a Sandy Soil Testing very High in Mehlich-1 P - Tomato (Lycopersicon esculentum Mill.) was grown in southeastern Florida on sandy soil that tested very high in Mehlich-1 P to evaluate the yield response to P fertilization.  One location was used in 1995-96, another in 1996-97.  Prefertilization soil samples contained 290 (location 1) and 63 (location 2) mg·kg^-1 Mehlich-1 P.  Both soil test results were interpreted as very high in P, and P fertilizer was not recommended for the crop.  Fertilizer treatments at both sites were 0, 25, 50, 100, 150, and 200 kg·ha^-1 P.  Neither total marketable yield nor yield in any fruit size category was affected by P fertilization in either season.  Amounts of cull (undersized or misshapened) fruits increased quadratically with P fertilization in the second season.  Whole-leaf P concentrations increased linearly or quadratically with P application, depending on sample periods, and were always above sufficiency values.  Although many tomato growers apply P fertilizer irrespective of soil test recommendations, our results showed that added P was not needed on soils testing very high in P.  Furthermore, withholding P applications to soils with high P concentrations will minimize potential P pollution of surface water and groundwater.

Nitrogen Fertilization to Maximize Carrot Yield and Quality on a Sandy Soil - Nitrogen is required for successful carrot production on sandy soils of the southeaster United States, yet carrot growers often apply N in amounts exceeding university recommendations.  Excessive fertilization is practiced to compensate for losses of N from leaching and because some growers believe that high rates of fertilization improve vegetable quality.  Carrots (Daucus carota L.) were grown in three plantings during Winter 1994-95 in Gainesville, Fla., to test the effects of N fertilization on yield and quality.  Yield increased with N fertilization but the effect of N rate depended on planting date; 150 kg·ha^-1 N maximized yield for November and December plantings but 180 kg·ha^-1 N was sufficient for the January planting.  Concentration of total alcohol-soluble sugar was maximized at 45 mg·g^-1 fresh root with 140 kg·ha^-1 N for 'Choctaw' carrots, whereas sugar concentration of 'Scarlet Nantes' roots was not affected by N fertilization.  Carrot root carotenoid concentration was maximized at 55 mg·kg^-1 fresh root tissue with 160 kg·ha^-1 N.  Generally, those N fertilization rates that maximized carrot root yield also maximized carrot quality as determined by sugar and carotenoid concentrations.

Evaluation of Two Soilless Growing Media and Three Fertilizer Programs in Outdoor Bag Culture for Strawberry in North Florida - Strawberry (Fragaria x ananassa Duch.) is a high-value crop in Florida produced on 6,000 acres annually.   An outdoor soilless bag culture system was evaluated during the 1997-98 season with two soilless media and three fertilizer programs using the strawberry cultivar 'Camarosa' at the Suwannee Valley Research and Education Center near Live Oak, FL.  The two soilless media evaluated were perlite and a peat mix.  Both media produced similar early, monthly, and total yield.  Total fruit yields were nearly one pound per plant.  The three fertilizer programs evaluated included two controlled-release fertilizer treatments and one hydroponic nutrient fertigation treatment.  No significant difference in total yield due to fertilizer programs was detected, with yields averaging between 0.90 and 0.94 lbs per plant.  Excellent strawberry yield and quality was found with these soilless bag culture systems, using either perlite or the peat mix as the media and any one of the fertilizer programs.

Evaluation of Several Cultivars of Cluster Tomatoes for Florida Hydroponic Greenhouse Growers - Several cultivars of greenhouse cluster tomatoes were evaluated in two season, 1996-97 and 1997-98.  The evaluations were conducted in small greenhouses at eh Suwannee Valley Research and Education Center near Live Oak, FL using the perlite bag culture system of production.  The production of several cluster tomato cultivars was similar to the standard beefsteak tomato cultivar, 'Trust', in both seasons.  Total marketable yield in both seasons was near 20 lbs per plant for the greater yielding cluster cultivars.  Average fruit weight varied in cultivars from 0.07 lbs for 'Aranca' to 0.30 lbs for 'E20.30090'.  Number of fruits per cluster also varied between cultivars from less than four to greater than seven.  Important postharvest fruit quality parameters such as russeting, luster, calyx appearance, and taste were also evaluated.

Growing 'Galia' Muskmelons Using Walk-in Tunnels and a Soilless Culture System in Florida and the Economic Feasibility of Using These Systems - 'Galia' muskmelons (Cucumis melo var. reticulatus L.) were grown under walk-in tunnels (quonset-style structures covered with a single layer of polyethylene film and heated and cooled passively without powered heating or cooling equipment) and low-tunnels (row-covers) during the winter/spring of 1997, the fall/winter of 1997, and the winter/spring of 1998 in Gainesville, Florida.  One-half of the walk-in tunnels contained thermal tubes (polyethylene tubes 30.5 cm in diameter that hold water which acts as a solar collector during the day and releases the energy as heat during the night).  In one-half of all rows under walk-in tunnels and low-tunnels, plants were cultivated in soilless culture using perlite as the medium.  Plants in the other one-half of each row were cultivated using soil-based culture with raised beds, polyethylene mulch, and drip irrigation.  This paper presents practical lessons learned regarding subjects such as temperature dynamics, humidity dynamics, and irrigation management while using walk0in tunnels and soilless culture to grow muskmelons in northern Florida during the winter.  We also estimated the economic feasibility of using these structure to commercially produce 'Galia' muskmelons.  The estimated break-even price for producing melons under 0.2 ha of walk-in tunnels in the spring with a yield of 60 MT_ha^-1 was $1.07 per kilogram with soil-based culture and $1.40 per kilogram with perlite-based soilless culture.   Fall/winter production of muskmelons was not economically feasible.

Nitrogen Fertilization of Florida-grown Tomato Transplants: Seasonal Variation in Greenhouse and Field Performance - Fall-grown tomato (Lycopersicon esculentum Mill.) transplants were larger than spring-grown transplants when fertilized in the greenhouse with NH3NO3 at 0, 15, 30, 45, 60, or 75 mg·L-1 N in a standard ¼ strength Hoagland’s solution. All transplant growth characteristics measured (stem length, leaf area and number, root and shoot dry mass) increased linearly with increasing N in both seasons. However, in the fall, when greenhouse temperatures and light levels were higher, stem length, leaf area, root:shoot ratio, and the ratio of shoot dry weight: leaf area responded quadratically. In the spring, total fruit yield and production of extra-large fruit increased with increasing transplant N fertilization, but the opposite trend occurred in the fall. These differing seasonal responses suggest fundamental differences in tomato transplant growth that must be addressed by modifications in N fertilization between spring and fall.