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Agricultural Extension ServiceThe University of Tennessee

PB 1609

CommercialCommercialCommercialCommercialCommercialGreenhouseGreenhouseGreenhouseGreenhouseGreenhouse

Tomato ProductionTomato ProductionTomato ProductionTomato ProductionTomato Production

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Table of Contents

Introduction............................................................... 4Tomato Production Systems .................................... 5Greenhouse Site Selection ....................................... 6Greenhouse Structures............................................. 6Cultivars or Varieties............................................... 7Growing Time ........................................................... 7Growing Plants ......................................................... 8Plant Spacings .......................................................... 9Estimated Costs and Returns ................................. 9Fumigation of Soil Systems .................................. 13Greenhouse Sanitation........................................... 14Rotation of Houses Used for Soil Production ...... 14Fertilization of Soil Systems ................................. 14Fertilization of Soilless Systems ........................... 15Identifying Nutritional Problems ......................... 21Trellising or Providing Supports .......................... 22Pruning ................................................................... 22Weed Control........................................................... 23Irrigation ................................................................. 23Light Requirements ............................................... 24Carbon Dioxide Enrichment .................................. 25Ventilation and Humidity...................................... 25Pollination ............................................................... 25Diseases ................................................................... 25Fruit Physiological Disorders ................................ 27Insects ...................................................................... 28Harvesting............................................................... 28Sorting and Packing ............................................... 28Storage..................................................................... 28Other References of Interest ................................. 30

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Commercial GreenhouseCommercial GreenhouseCommercial GreenhouseCommercial GreenhouseCommercial GreenhouseTomato ProductionTomato ProductionTomato ProductionTomato ProductionTomato Production

IntroductionGreenhouse tomato production offers inter-

ested growers an opportunity to produce a mar-ketable product at times when supplies are low.It increases the length of time tomatoes areavailable and improves buyer interest in thearea. However, greenhouse tomatoes must be soldfor a higher price per pound than field tomatoesto justify the higher production costs. Thismeans the system offers profitable opportunitiesin the spring before field tomatoes are harvested,and in the fall when field tomatoes have beendepleted. Greenhouse tomatoes are usually grownfor local sales in Tennessee.

In the spring, plants set more fruit per plantand the heating cost is less, making spring pro-duction more profitable than fall production. Also,in the spring, light intensity and duration in-crease as outside temperatures increase, makingit less costly to heat and provide ventilation andhumidity control. All of these result in increasedyields. In the fall, increased heating costs, greaterpollination labor and lower fruit set occur at atime when the average price is not as high as inthe spring, resulting in lower profits. However,research being done at The University of Tennes-see indicates that fall tomatoes can be profitablyproduced if plants are transplanted by August 15.

Disease and insect problems can be majordifficulties in greenhouses. To reduce such prob-lems, growers must develop good sanitation,prevention and ventilation programs. Just becausecrops are grown in enclosed structures does noteliminate such problems.

In addition, interested growers should keepin mind that:

1. Greenhouse tomatoes have cultural require-ments unlike other crops, such as field toma-toes, tobacco and other crops common toTennessee. Even growers of field tomatoes may

have difficulty growing greenhouse tomatoeswithout a significant amount of learning time.The management practices are different fromthose of field tomatoes and will require someproduction experience.

2. Greenhouse tomatoes are not an easy crop togrow profitably. Growing time, temperatures,pollination, irrigation, fertilization, disease andinsects, as well as weeds in a soil system,require different management techniques thanoutdoor crops. Fertilization of hydroponicsystems requires both good management prac-tices and a knowledge of how to mix and applynutrient solutions in accordance with cropgrowing conditions. Because of the differencescompared to field tomatoes, it is more difficultto grow them in greenhouses.

3. The labor necessary to grow greenhouse toma-toes is much greater on a per-unit basis thanthat of any field or vegetable crop. The produc-tion practices involved require a significantamount of time. The estimated average laborrequirement for a 30-foot by 100-foot green-house is about 25 person hours per week. Withgrower experience, this time may be reduced.More time is needed during transplanting andharvest, but less time per plant will be re-quired from transplanting to harvest. Makeadequate labor provisions before the labor isactually required.

4. Greenhouse tomatoes require attention on aconsistent basis. They cannot be planted andthen forgotten for a few days or weeks, assometimes occurs with other crops. Becausethere are so many problems that can arisequickly, they require daily observation andattention during the growing season, and thehouse will require a sanitation program be-tween crops.

Alvin D. Rutledge, ProfessorExtension Plant and Soil Science

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5. The greenhouse environment is not problem-free. The problems with greenhouse tomatoesare almost analogous to raising animals inconfinement. The higher humidity, temperatureand lush green foliage create conditions thatenable certain diseases and insects to thrive. Inaddition, pollination is affected because of lesspollen shed. Under these conditions, houseventilation management and pest control pro-grams are essential requirements of production.

Tomato ProductionSystems

Two systems exist for greenhouse tomatoproduction. They are referred to as either soil orsoilless culture. Soil culture means that tomatoesare grown under a greenhouse cover in a plot ofsoil using similar techniques to those used in thefield. Soilless culture (also called hydroponics)refers to growing tomatoes where the necessaryfertilizers are delivered to the root system inbalanced levels in water solution. With soillesssystems, plant roots are growing in water, sand,wood bark or an artificial soil mix availablethrough various greenhouse suppliers.

Of the two systems, the soil system hasproven to be the most widely used in Tennessee.Counties using this system have usually increasedtheir number of greenhouses, while most soillesssystems have not remained in operation for morethan two or three crops due to the high initialcost.

Soil: When the soil system is used, theoverall house construction cost is about one-fourthto one-third that of certain soilless systems. Soilsystems enable the movement of a house to a newlocation after two or three years’ production if soildisease problems result. The land can then be usedto grow a different crop.

With the soil system, a greenhouse structureis constructed over the designated plot of land.There is no land excavation involved as in soillesssystems. The house is constructed to fit the slopeof the land. Fertilization and staking are almostidentical to that of field tomatoes. The house isconstructed to enable maximum ventilation. Thisusually includes double-wide doors at each endwith fans positioned high enough in each end toreduce the potential for cold air to be ventilateddirectly onto the growing plants. Such houses mayalso have side roll-up capability or windows to

increase the ventilation. Double-wide doors alsoenable the movement of both land preparation andcultivation equipment into the house.

If a fall crop is to be grown in a soil system,it is best to start and grow plants under naturalweather conditions for about 1 to 11/2 monthsbefore the greenhouse must be closed continuously.This will enable plants to get off to a good startand will increase the potential for good set on thefirst fruit clusters. However, irrigation will benecessary to grow the plants due to the hot, dryweather that is likely at the time of transplantingin August. Drip irrigation is the preferred type touse in greenhouse systems.

Soilless: Nutrient delivery systems andnutrient holding tanks for certain types of soillesssystems are being sold with permanent installa-tions that cannot be conveniently moved. Thesesystems require nutrient troughs, plumbing,pumping systems and stock tanks. When theybecome contaminated with bacteria or fungi, avery rigid and costly sanitation program must beimplemented between each crop. Once contamina-tion becomes prevalent, it is very costly to movesuch a facility. The presence of higher levels ofwater in certain systems increases greenhousehumidity, making humidity control more difficultthan in soil houses. In addition, such systemsfrequently use expensive and complex computersystems. However, it is possible to develop soillessnutrient tanks that are portable and less costlythan permanent systems. Some systems include the“grow-bag” and “composted-cotton” artificial mediathat add water and nutrients through drip tubing.Such systems are normally less expensive thanother soilless systems and they can be used incombination with growers who grow plants usingthe “float system.”

Nutrient solutions must be mixed, main-tained and delivered through a trough or pipedelivery to the root system on a regular basis.The nutrient pH and nutrient balance are quiteimportant, since there are 13 nutrients requiredfor production. Each has a different concentrationrequirement in the nutrient solution that must bemaintained. Obtaining both proper balance andapplication frequency based on plant utilization isnot a task for an individual who has no experi-ence with such systems.

To illustrate the different concepts of produc-tion, a schematic diagram of the interior of thetwo systems is provided in Figure 1.

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Trickle irrigation system

Nutrient solution pumped through troughs

Plants

Nutrient trough

Nutrient storage tank

Figure 1. Illustration of basic greenhouse systems (soil house on left. Soilless system on right.)

Greenhouse SiteSelection

Select a site that is in full sun and slightlyelevated so there will be good air movement andventilation. If soil culture is planned, the soilshould be well-drained, medium-textured and fertile.Avoid sites with a history of disease or weed prob-lems. If the site is infested with a perennial weed,it may need to be treated with Roundup® prior toconstructing the house. Treat while the weeds areactively growing. Locate the site near a clean watersupply that is adequate for the size of house desired.

For soil culture, the floor can be either level orsloped if trickle irrigation is planned. Certainsoilless systems require level floors to install thegrowing troughs suitable for nutrient deliveryacross the roots. The “grow-bag” system is feasibleon sloping land with trickle irrigation.

Greenhouse StructuresQuonset-type greenhouses using galvanized

pipe as the main structural materials with double-

layer polyethylene (plastic) covers are the mostcommon type of greenhouse structures, regardless ofthe production system being used. Double-layer polyis separated by a small fan delivering air betweenthe two layers. This reduces the heat cost by 30 to40 percent compared to a one-layer system. Thesegreenhouses are the most economical to constructand to move if necessary.

For soil culture, the supporting structures anddouble-wide end doors should be constructed toallow the use of small tractor equipment withinthe house. The double doors can provide ventila-tion capability, as well as allowing equipmentaccess for cultivation or soil preparation. Housesidewalls can be constructed to enable side roll-downs or draw-down windows to increase airmovement during appropriate weather conditions.Continuous soil culture may require fumigation tokeep disease problems to a minimum. Treatmentsare more effective if the fumigant is injected andcovered with plastic. This type of construction alsomakes land preparation and plant residue removalmuch easier.

Design heating capabilities into a greenhousestructure to provide plant protection during the

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cooler growing months. Also, install cooling fansand small doors for days when the large doorsshould not be completely opened.

Due to the plant supports required, certainsoilless culture structures will require strongersupport and bracing structures than a soil house.In many situations, soilless-culture tomatoes aresupported by drop strings from overhead pipes toindividual plants below. One row of tomatoescontaining 80 plants in a 100-foot house has thepotential to develop up to 1500 pounds of weightthat requires support. Thus, if all rows are sup-ported from drop strings from the overhead sup-ports, the potential weight load from plants andfruit will approximate five tons. Supports for soilproduction are provided by stakes, the same as forfield tomatoes.

Cultivars or V arietiesThe first step to growing good greenhouse

tomatoes is to select a cultivar or variety thatproduces the size, shape and color of fruit desiredfor the market. The cultivar or variety you chooseshould also set a high number of fruit per plant.Because of high production costs, the number offruit per plant is very important when consideringthe potential for a profitable operation. Even thoughseed costs are quite high for hybrid seed, seeds arestill the least expensive cost involved in growinggreenhouse tomatoes. Thus, a grower should notlook for the lowest cost seed when choosing acultivar because it is impossible to produce a good-quality product from low-quality seed or plants.There are many cultivars of tomatoes on the mar-ket, but only a few have been developed specificallyfor growing in greenhouses. However, growers arelearning that certain other varieties will produce asuitable product.

Cultivars for Soilless Culture: Tomatocultivars for production in greenhouses have beendeveloped primarily in Holland. Thus, several of theseed companies that supply them are in Hollandand other European countries. Some, however, havedistribution points in the United States. They areDe Ruiter Seeds, Inc. (614-459-1498), BruinsmaSeeds (owned and distributed by Asgrow (601-845-7125) and Nunhems (Canners Seed Corporation inthe U.S., 208-754 8666). Cultivars that are pres-ently being grown are ‘Caruso’ and ‘Trust’ from DeRuiter and ‘Dombito’ and ‘Dombello’ from Asgrow-Bruinsma, as well as Rupp Seeds in the U.S.

(419-337 1841). ‘Trust’ is showing very good perfor-mance in the fall at The University of Tennessee inKnoxville.

Cultivars for Soil Culture: Establishedgreenhouse tomato growers are presently growingthe determinate varieties, “Celebrity,” “MountainPride” and “Mountain Fresh.” A ‘determinate’ typeis one that normally sets a high number of fruit ona plant that stops growing at a height of 4 to 5 feet.However, a few growers are still growing the‘indeterminate‘ (one that does not terminate growthat a low height) types such as “Better Boy” and“Fantastic.” These cultivars are available fromseveral U. S. seed companies.

Growing TimeThere are two periods for economically growing

greenhouse tomatoes in Tennessee. One is in thespring and the other is in the fall.

Spring: For spring production, time the crop totransplant in the greenhouse in late February orearly March. This means that seeding must be donethe last week of December or in early January.Both personal observation and grower experienceindicate that this is a relatively good time to growspring tomatoes. Plants are transplanted at a timewhen the heat requirement is decreasing, daylength and light intensity are increasing andoutdoor temperatures are increasing. This makes itmore conducive for daily ventilation. Ventilationhelps in drying the tomato foliage and reducingdisease problems, as well as improving pollen sheddue to a lower humidity in the greenhouse, com-pared to poor ventilation and high humidity. Expe-rience has shown that keeping the foliage as dry aspossible with sufficient air movement to enhancepollen shedding has more than doubled per-plantyields. Due to these factors, spring production ispracticed more widely than fall production.

Fall: Present research work being conducted atThe University of Tennessee in Knoxville andcooperative trials with local growers indicate that itis possible to profitably grow fall tomatoes if plantsare transplanted to the greenhouse by August 15.Planting at this time enables plants to set a highnumber of fruit while the temperatures and lightintensity are still high, ventilation is still quitefeasible and heating requirements are low. Highnumbers of fruit per plant set under these condi-tions can usually be matured at a profit.

Questions may arise concerning production inDecember, January, February and March. If tomatoes

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can be grown profitably at this time, there isusually no problem in selling them on a local retailmarket. However, there are more serious problemsin obtaining a profitable yield during these monthsthan during the spring or fall. Low outdoor tem-peratures make it highly improbable to providegood ventilation to control humidity. Under suchconditions, leaf mold usually becomes a majorproblem. Flowering and fruit set are reduced, whichresults in low yields per plant. Low light intensityreduces fertilizer uptake, resulting in reduced fruitsize and visual fertilizer deficiency symptoms on thefoliage. Heat costs increase due to lower tempera-tures, resulting in higher production costs. Ingeneral, producing during the winter has notproven to be profitable due to high fuel costs andlow yields.

Growing PlantsA major recommendation is to start plants and

grow them under disease-free conditions. It is muchbetter to grow your own plants rather than riskimporting certain diseases or insects that transmitdiseases. Plants can either be grown in a green-house with protective systems for a spring crop, orthe “float plant” system can be used to effectivelystart plants for a fall crop. For further informationon growing plants, refer to Extension PB 819,“Vegetable Transplant Production,” available atyour county Extension office. When plants aretransplanted to the greenhouse, they should not beinfested with diseases. Starting with plants that aredisease-free increases the potential for controllingdiseases during the growing season.

Use sterilized growing media and growingcontainers. Start plants from seed rather than usingsuckers from an already-existing crop. Suckers mayalready be heavily infested with diseases such asearly blight if good control programs have not beenpracticed.

Start seed in seed flats and transplant toindividual containers or to plant cells (when usingthe float system) when the first true leaves arevisible. Keep the growing media moist but notsaturated. Depending upon the fertilizer suppliedwith the growing media, it may be necessary toprovide low levels of fertilizer during the growingstage. When the float system is used to grow fallplants outdoors, about six ounces of water-soluble20-20-20 fertilizer per 100 gallons of water shouldprovide plants about 8 inches tall within five or sixweeks. Plants grown in the “float system” for fallproduction will need to be hardened for a few daysbefore they are transplanted to the greenhouse.Plants can be easily hardened by removing themfrom the float bed about one week prior to theexpected transplant date. They can be held inpartial shade for a day or two, then moved to fullsun with appropriate watering as necessary.

The conditions under which plants are grownwill influence the number of flowers formed and thenumber of fruit set per cluster. For spring plants,research has indicated that the number of fruit onthe first cluster is increased if the nighttime tem-perature can be held between 50 and 55 degreesfrom first true leaf development until the firstflower cluster is fully developed. To obtain maxi-mum yields, try to set an average of five to sevenfruit per cluster.

Temperature conditions suitable for good plantgrowth are outlined in Table 1.

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)Fseerged(erutarepmeT

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.noitanimregdeeS.1 07-56 07-56

anigeb,dlofnusevaeldeesretfa,porcgnirpsroF.2.syad41-01rofeunitnocdna"tnemtaertdloc"

55-35 06-55

detnalpsarterastnalplitnu"tnemtaertdloc"morF.3.esuohneergotni

56-06 07-56

.gnitiurfdnagnirewolfgniruD.4 56-06 68-56

Table 1. Temperature Requirements for Growing Greenhouse Tomatoes

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Seeding DatesThe approximate seeding dates for two crops are:Spring crop: Late December through early JanuaryFall crop: Late June through early July

Transplanting DatesTransplanting into the greenhouse should

occur about seven to eight weeks from the seedingdate, or about February 25 to March 5 for a springcrop, and August 10 to 20 for a fall crop. Avoidsetting plants on a ridge. This makes roots verysusceptible to damage by cultivation.

Plant SpacingsSoil Systems: For the soil system, plants can

be spaced 15 to 20 inches apart in the row and 42to 54 inches between rows. This will accommodategood movement about the plants for suckering,supporting, spraying and harvesting. Plants grownin a soil system are usually trained, staked and tiedusing the “Florida Weave” system common to fieldproduction. For further information about thissystem, refer to Extension PB 737, “StakedTomato Production in Tennessee,” available atyour county Extension office.

Soilless Systems: For the soilless system, 42-inch wide troughs can be used to grow two rows,with plants spaced 10 inches inward from each sideof the trough and on a 18x24 inch spacing, asillustrated in Figure 2. Growers who use the “grow-bag” system normally lay the bags end-to-end, spacetwo or three plants per bag, and separate themabout 31/2 feet between rows.

Tomatoes grown in soilless systems areusually trained to a one-stem system due to thecloseness of plants. However, growers can avoidheavy pruning by wider spacings, if desired.

Plants RequiredThe plants required in a 30-foot by a 100-foot

greenhouse at spacings for the two systems areshown in Table 2.

Table 2. Plant spacings and plant requirements forgreenhouse tomatoes.

Soil Systems

Soilless Systems

Estimated Costsand Retur ns

Spring Crop Grown in Soil: The followingbudget is merely a guide to estimating costs andreturns for soil-produced tomatoes grown in thespring in a 33-foot by 144-foot greenhouse. (Itshould be used as a guide only because there is noguarantee that the figures provided will fit all

20˝

24˝

10˝

Figure 2. Schematic of a trough used forsoilless production of tomatoes

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worneewteB)sehcni( )sehcni( )sehcni( )sehcni( )sehcni(

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latoTstnalp stnalp stnalp stnalp stnalp

51 24 8 046

51 84 7 065

51 45 6 084

81 24 8 535

81 84 7 664

81 45 6 004

02 24 8 084

02 84 7 024

02 45 6 063

hguorThtdiw htdiw htdiw htdiw htdiw

tnalPgnicaps gnicaps gnicaps gnicaps gnicaps

repstnalPhguort hguort hguort hguort hguort

latoTstnalp stnalp stnalp stnalp stnalp

esuohrep esuohrep esuohrep esuohrep esuohrep

"24 "51x"02 441 027

"24 "42x"02 09 054

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situations. Growers must use their own figures inplace of those included in this budget example whenthat information is known.)

House Cost: Double-layer polyethylene covered;$13,500 prorated 5 years = $2,700 per year.

a. If house is prorated 3 years, annual cost is$4,500/year.

b. Every third or fourth year, replacement of plasticmust be included into the cost.

Table 3: Yields of 13 pounds per plant and 900 plants per house (This budget assumes top greenhousemanagement and production practices.)

Revenue:

Expenses:

Prorated house cost= 5 years $2,700.00Prorated construction cost($0.65/ft2 if done by self) 561.60a

Plants; $.06 to grow x 900 plants 54.00Total heat cost Jan - April 1,900.00Electricity 50.00Stakes and string 69.50Bumblebees for pollination 190.00b

Fertilizer and lime 11.00Fungicides 20.00Insecticides 20.00Irrigation supplies 70.00c

Irrigation water (if purchased) 200.00Baskets 195.00Labord 891.00Transportation 150.00Interest ($13,700 @ 7.25%) 978.75e

Total expenses $8,060.85f

a. Construction costs are pro-rated five years for a total of $2,808.b. A new hive should be purchased with each crop.c. Irrigation supplies such as pumps, fittings and carrier lines are pro-rated for three years. However, unless

a loan is taken to provide for this expense, the total cost is up front and is not pro-rated. Thus, this couldbe a one-time cost with the addition of replacement materials during the second and subsequent years.

d. Labor is calculated at $5.25 per hour for a total of 170 hours.e. Interest is included for a full year because it is assumed that a loan made over a 5-year period will prob-

ably require annual payments. However, as the principal is paid, the annual interest will decrease, causingthe per-plant profit potential to increase.

f. This does not include a brokerage fee or insurance.

Returns $2,837.15

tsevraHnosaes nosaes nosaes nosaes nosaes

fonoitubirtsiD)%(selasporc )%(selasporc )%(selasporc )%(selasporc )%(selasporc

sdnuoplatoTdlos dlos dlos dlos dlos

repecirPdnuop dnuop dnuop dnuop dnuop

latoTeunever eunever eunever eunever eunever

ylraE 04 0864 02.1$ 616,5$

diM 04 086,4 09. 211,4

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latoT 001 007,11 .vA39.0 898,01$

.dlossdnuoplatotybeuneverlatotehtgnidividybdenimreteD.a

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Table 4: Net Return from Greenhouse Tomatoes at Varying Per-plant Production Costs and with High Yields

tsoclatoTtnalprep tnalprep tnalprep tnalprep tnalprep a

:fosdleiytnalp-reptadnabl/39.0$foecirp.vanatatnalp/nruteR

.sbl11 .sbl21 .sbl31 .sbl41 .sbl51

59.01$ )27.0($ b 12.0$ 41.1$ 70.2$ 00.3

07.9 35.0 64.1 93.2 23.3 52.4

59.8 82.1 12.2 41.3 70.4 00.5

64.8 77.1 07.2 36.3 65.4 94.5

01.8 34.2 60.3 99.3 29.4 58.5

a. Each of the figures in this column represents the per-plant production cost when the house cost is pro-rated 3, 4, 5, 6 and 7 years, respectively.b. Numbers in parenthesis are negative. This means that either the production cost must be lowered or the yield must be higher to have a potential profit.

There have been situations when yields are much lower than those shown in Table 4.

However, total production costs do not change greatly when low yields occur. Let’s consider the netreturns under lower per-plant yields.

Table 5: Net Return from Greenhouse Tomatoes at Varying Per-plant Production Costs and with Low Yields

tsoclatoTtnalprep tnalprep tnalprep tnalprep tnalprep a

:fosdleiytnalpreptadnabl/39.0$foecirp.vanatatnalp/nruteR b

.sbl4 .sbl5 .sbl6 .sbl7 .sbl8

59.01$ )32.7$( )03.6$( )73.5$( )44.4$( )15.3$(

07.9 )89.5( )50.5( )21.4( )91.3( )62.2(

59.8 )32.5( )03.4( )73.3( )44.2( )15.1(

64.8 )47.4( )18.3( )95.2( )59.1( )20.1(

01.8 )83.4( )54.3( )25.2( )95.1( )66.0(

a. Same as “a” in Table 4.b. This table is included to allow a comparison of the potential profit when production costs do not

change, but yields are low. Numbers in parenthesis represent a negative profit. It is obvious from thesefigures that low yields are not a paying proposition at the per-plant production costs provided. Produc-tion under such conditions should be avoided. Low yields can result from improper planting time,improper ventilation, low light intensity, high nitrogen, improper nutrient balance, low pollination,incomplete combustion of heating materials and many other factors. Thus, any grower contemplatingproduction under such systems must thoroughly weigh production practices that will consistentlymaintain high yields.

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Comments: The above returns and expensesrepresent the economics of systems where growerstransplant tomatoes into the greenhouse in lateFebruary or early March. There is no cost for houseexcavation because production occurs in housesadapted to the existing slope. Under such condi-tions, growers have normally completed harvest bythe time field tomatoes from the area appear on themarket. As a result, greenhouse growers normallyreceive a higher price than those with field toma-toes. However, the higher production costs indicatethat greenhouse growers need to obtain good pricesto be profitable.

Fall tomatoes: From the present researchdata at The University of Tennessee in Knoxville, itappears that tomatoes grown in containers withartificial growing media may turn a profit if theyare transplanted by August 15 and are completelysold out by late November or early December. Thereason is that certain production costs can bereduced in the fall compared to planting later thanAugust 15. However, the statements that followshould be considered when evaluating the potentialfor fall tomatoes. Present research indicates thatthe greenhouse-developed variety “Trust” is produc-ing yields in the 10 pound per-plant range duringthe fall rather than 12 to 15 pounds now commonlyproduced in the spring. This is almost doubleprevious fall yields from research efforts in Knox-ville. With lower production costs for an August 15planting compared to later fall planting, one canevaluate the returns per plant at a lower yield inTable 4, even though 10 pound per-plant yields arenot provided in either Table 3 or 4.

Some tobacco growers who grow plants in floatbeds and who have an interest in greenhousetomato production for times when their house is notbeing used should grow fall tomatoes in artificialmedia or “grow bags.” Balanced fertilization canthen be provided through a trickle irrigation sys-tem. Where excavation of the property has occurredfor the construction of float beds, it is not suitableto produce tomatoes in the excavated soil. To do sowould require the replacement of top soil.

If tobacco producers growing float plants usetheir houses for tomato production, it is not likelythat there will be a transfer of compatible diseasesif there is a good sanitation program between thetobacco and tomato crops. Sanitation, however, is akey to reducing the potential for disease transfer.Sanitation should include changing the plasticliners used in the float beds and sterilizing exist-ing concrete walkways, as well as existing walls

and containers, by rinsing with a 10 percentchlorine solution.

In addition, the following cost-and-return itemsare likely to be different for fall tomatoes than forspring tomatoes.

1. Heat costs are likely to be about one-third lower ifplants are transplanted no later than August 15.

2. Yields may be one-fourth to one-third lower thanspring tomatoes due to lower light intensity,lower temperatures, less ventilation and pollina-tion capability.

3. Fertilizer costs will probably increase in certainsoilless systems, compared to soil culture, becauseof the necessity to provide water-soluble fertilizerand the labor involved in application. In addition,fall’s low light intensity is likely to require adifferent frequency or rate of fertilizer applicationthan spring-produced tomatoes.

4. Prices are not likely to approach the $1.20 perpound level common for spring tomatoes until allfield tomatoes have cleared the market. However,some observations indicate that November/December tomatoes may receive slightly higherprices than the $1.20 per pound spring prices dueto a low supply.

5. Ventilation requirements for August 15-trans-planted tomatoes are high. Temperatures will bevery high under the plastic cover during thistime of year.

6. Because of higher temperatures, water require-ments during August and early September willbe very high for plant survivability, but willdecrease as temperatures cool down. In thespring, the reverse is true as water requirementsincrease with temperature, foliage and fruit load.

7. As the growing season moves further into thefall, temperature problems will be less, and lightintensity, humidity and ventilation problems willincrease, resulting in decreased fruit set.

8. If a greenhouse has been excavated for float bedtobacco plant production, an excavation chargeshould be included in the above budget. Thiswill provide an estimate of the profit potential ifthe excavation charge is to be pro-rated acrossboth crops.

Markets: Unestablished growers will have todevelop markets. Generally, buyers who have dealtwith dependable growers over the years are reluc-tant to deal with someone who has not been in thebusiness and has not yet developed a reputation asa dependable supplier. In the fall, it is likely that alocal area could easily support tomato sales from

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one or more houses in that area. To evaluate whole-sale profit potential, growers should have somewholesale price figures for the time of year theywill be selling. Prices under those conditions arelikely to be different from the $0.93 per poundaverage used to estimate returns in this budget.

The initial cost of a complete hydroponic houseis two to four times that of a soil house, while theyields per plant are generally no greater with anequal growing time. Thus, the potential return oninvestment is usually less with a hydroponic housethan with a soil culture house.

Fumigation ofSoil Systems

Soil culture will eventually require the soilto be fumigated if continuous production occurs inthe same location. Control will be needed for increas-ing problems with nematodes, verticillium, fusariumor various bacterial diseases. Unfortunately, fumiga-tion will not eliminate all of the problems associatedwith greenhouse tomato production, but it will helpto hold certain problems at a manageable level.However, manufacture and sale of the most com-monly used fumigant, methyl bromide, is scheduledto be stopped by 2002. At the present time, there isno suitable substitute. However, work is under wayto develop suitable replacements.

Remember to construct the house to allowsmall tractor equipment to enter and prepare thesoil and to inject any planned fumigation materials.Best control occurs when the fumigant is injectedand then covered with plastic. Due to warmer soiltemperatures, fumigation is more effective if donein the fall. Fall fumigation also does not delayspring transplanting in February or March.

Plant residue must be either completely re-moved or turned under at least six weeks ahead ofthe planned date of fumigation. The residue must becompletely decayed before fumigation or it will blockthe injectors, giving poor fumigation results. The soilshould be prepared to a minimum depth of about 6inches, preferably with a rototiller. This prepares thesoil for satisfactory fumigation. It pulverizes largeclods and assists in further breakdown of plantresidue to enable effective and uniform injection.

The soil temperature must not be below 60F orthe fumigant will freeze on the injectors and blockapplication. The best soil temperature for fumiga-tion is 70F or above.

Fumigation is expensive and, if done, requiressmaller equipment than that commonly used in thefield. Suitable injector equipment should be designedand constructed by the grower, since presentlyavailable equipment is too large for use in mostgreenhouses. The fumigation equipment shouldcontain a fumigant tank, carrier tank, control valvesand hoses from the tanks to the injector. The systemis mounted on a three-point, hitch-connected framewhich injects the fumigant through injector knives,installs a plastic cover over the fumigant-treatedstrip and seals it, all in one operation. The injectorwidth should be wide enough to make five or sixpasses through a 30 ft.wide house. The fumigationtechnique could be done in strips in the greenhousein the same manner as is common in the field. Astrip as wide as the injector is treated, then a stripof the same width is skipped. The tractor could bebacked the entire length to begin the next treatedstrip. Use methyl bromide formulations, “Vorlex” orother suitable fumigant according to manufacturer’sdirections. This is repeated until the entire area iscovered. The untreated strips are treated about threeor four days later, after the plastic from the firsttreated strips is removed. This technique is illus-trated in Figure 3.

Caution: Methyl bromide, if used, is a verytoxic material. Thus, during the fumigation process,the house should be kept under maximum ventila-tion to remove any escaping gas. In addition,applicators should wear protective clothing andfacial protection at all times.

Figure 3: Illustration of fumigation procedure wheretomatoes are grown in the soil.

Untreated

Untreated

Untreated

Treated

Treated

Treated

House is 30 ft. wide—6 strips each 5 ft. wide

14

Greenhouse SanitationGood sanitation programs are paramount to

keeping disease and insect problems at a minimum.These pests can greatly reduce marketable yields ifthey are not kept under control. One way to reduceproblems is to provide a good sanitation program. Agood sanitation program, for both soil and soillesssystems, includes:1. Sterilizing all plant-growing containers and trays

between each crop. Rinse each with a 10 percentchlorine solution followed by a water rinse, andthen aerate for three to four days before using.

2. Do not transfer disease-infested plants to thegreenhouse.

3. For soil culture, the soil should be fumigatedbetween crops and houses should be rotated everythree or four years. In soilless culture, growingtroughs, trays and nutrient solution stock tanksshould be cleaned between crops.

4. Remove and destroy all plant residue as soon asthe crop is finished. Wash the walls with asterilizing solution.

5. Do not work in an infested area and then moveto an uninfected area without cleaning hands,equipment and clothing.

6. Before entering a house, dip the soles of shoes ona pad saturated with a disinfectant.

7. Keep weeds and grasses adjacent to the green-house under control to reduce the habitat forpests.

8. Irrigate plants by applying water to their baserather than by using sprinkler irrigation. Sprin-kling wets the foliage, encourages fungal andbacterial development and may contribute to areduction in pollen shed.

9. Keep windows and vents covered with screens toprevent insect movement and wind-blown weedseeds from entering the house.

Rotation of Houses Usedfor Soil Production

With soil culture, it is possible for continuouscropping of tomatoes to result in high populations ofnematodes, verticillium, fusarium, botrytis, greymold or even an increase in insects such as pin-worms or white flies. Fumigation, sanitation, theuse of resistant cultivars, etc. will reduce theseproblems, but it is also possible, and expensive, tomove a double-layer polyethylene greenhouse everythree or four years to further keep these problemsunder control. If double-layer polyethylene is used,

it should be replaced about every three or fouryears. This is an excellent time to rotate house sitesif problems become uncontrollable.

If a soilless system is used that requires theconstruction of nutrient-holding tanks and nutrientdelivery systems with considerable plumbing,rotation of houses is not very practical due to thecost of construction.

Fertilizationof Soil Systems

When spring tomatoes are grown in green-houses with soil, growers can use about the samefertilizer programs that are used in the field. Besure to take soil samples prior to planting. Goodcalcium levels, above 500 pounds per acre, shouldbe available to reduce blossom-end-rot. The pHshould be 6.1 or above.

Lime and fertilizer used in soil systems can beapplied and worked into the soil before planting,just as they are applied to field tomatoes. Table 6provides the lime and fertilizer recommendations forsoil-grown greenhouse tomatoes.

Table 6. Recommended Fertilizer Ratesfor Soil Systems

.tf.qs0001/.sbl(rezilitreF

negortiN

lioStset tset tset tset tsetslevel slevel slevel slevel slevel P2O5 K 2O

gnitnalpta5.1 a L 6 6

gnisserdedis5.4 b

M 3 3

H 2 2

HV 0 0

a/ 1.5# of N can be supplied by 4 lbs. of ammonium nitrate.b/ Split this amount into three equal applications

and apply the first sidedressing when the firstfruits are about 1 inch in diameter. Repeat twiceat four-week intervals.

Lime applications will be based on both thewater pH and buffer pH. Thus, a standard limeapplication is not included because of variations inboth water pH and buffer pH.

If trickle irrigation equipped with a fertilizerinjector is used, it is possible to apply a water

15

soluble fertilizer such as 20-20-20 or other suitablewater-soluble fertilizers through the system. How-ever, it may be difficult to meet the total fertilizerrequirements with 20-20-20, especially when phos-phate (P205) and potash (K20) both vary in soilresidual levels. If application is made based on theP205 requirements at either the medium or highlevel, then nitrogen levels are likely to be too low.If applications are made based on the nitrogenrequirements, then P205 or K20 will be applied inexcessive quantities.

In soil systems, one half of the recommendednitrogen and potassium and all of the recommendedphosphate are applied prior to planting. A phos-phate material commonly used includes 0-46-0applied as in the field. The remaining one half ofthe nitrogen and potash can be distributed throughthe trickle system directly to the root zone on adaily or weekly basis. The fertilizer material mostcommonly used to meet these needs in the field iswater-soluble potassium nitrate (16-0-44). Theapplication rate is normally based on the nitrogenrequirements with no emphasis given to potash.

Determining Trickle Rates of Nitrogen forSoil Systems: To figure the rate of 16-0-44 requiredto meet the remaining one half of the nitrogenrecommendations, multiply the nitrogen rate peracre times the percent of an acre that the housecovers, and divide by the percentage of nitrogen inKNO3 (potassium nitrate). For example, a 30-by-100foot house is 3000 sq. ft., which is 7 percent of anacre. Thus, if a total of 120 pounds of nitrogen isrecommended per acre and 60 pounds were appliedat planting, then 60 more pounds are to be distrib-uted over the remaining growing season of about 12weeks. Thus, 60 x 0.07=4.2 lbs. nitrogen divided by0.16 (16% N in 16-0-44) = 26.25 pounds of KNO3 tobe applied over the 12-week period. If it is to beapplied weekly, then 26.25/12 = 2.18 lbs. x 16 ozs.per pound = 35 ozs. to be injected through thetrickle system per week per house. By the sametoken, it would require a total of 28 ounces of 20-20-20 to provide equivalent levels of nitrogen.

Almost all of the minor elements required forgrowth will be supplied by the soil when soilsystems are used, if the pH is maintained in thefavorable range and the soil is not sand.

Fertilization ofSoilless Systems

When soilless systems are used, a plumbingsystem must be provided that allows frequentdeliveries of water-soluble nutrients to the rootzone. The frequency of delivery will depend uponthe growing media. Sand will require more frequentdelivery than an artificial mix of peat moss, perliteor vermiculite, due to the nutrient retention differ-ences. Soilless systems require that appropriateconcentrations of each of 13 nutrients be supplied tothe plants. The required concentration varies witheach nutrient. In most cases, the best way toaccomplish this is to purchase pre-mixed, water-soluble nutrients and mix them into the appropriatewater volume suggested by the manufacturer.

This stock solution is pumped daily on anintermittent basis. It is constantly monitored andadjusted to maintain the proper concentration ofeach nutrient and solution pH. The daily frequencyof nutrient delivery will depend upon the weather,with more cloudy days receiving a lower number ofdaily feedings and sunny days receiving a highernumber. Recycling nutrients may cause a majorproblem by creating the potential to pick up certaindisease organisms and distribute them throughoutthe greenhouse.

pH of the Nutrient Solution: The pH of aplant nutrient solution should be in the 5.6 to 5.8range to keep nutrients from becoming unavailable.Too high pH (greater than 6.5) increases the poten-tial for micronutrient deficiencies. Too low a pH(less than 5.3) may result in calcium or magnesiumdeficiency or manganese toxicity. Thus, the nutrientsolution pH should be checked every time a solutionis prepared. A pocket pH meter is not an extremelyexpensive tool. As long as it is kept properlycleaned and maintained, it is a good quick checkand should be a tool for every greenhouse grower.

If the pH of the solution is too high due toalkaline water, add an acid in small quantities tolower the pH into the 5.6 to 5.8 range. Allow thesolution pH to equilibrate after the addition of acid,then recheck the pH. Acid-supplying materialsinclude sulfuric acid (H2S04), nitric acid (HNO3) andphosphoric acid (H3PO4). Sulfuric acid is the leastexpensive of the above materials and can be pur-chased from an auto supply store as battery acid.Even though they are expensive, there is an advan-tage to using either nitric or phosphoric acid due tothe nutrients they can supply.

16

Caution: When handling acids, remember thatthey are hazardous and can result in considerabledamage when mishandled. It is best to use themdirectly from the original container so there is norisk in pouring them.

To determine how much acid to add to a tankor bulk container of nutrient solution, use onegallon of the solution and add one milliliter of acidat a time until the pH is in the desired range. Thenmultiply the amount in milliliters times the num-ber of gallons in the tank. This is the quantity ofacid needed per tank. Remember, one pint is equalto 473 milliliters or 1,000 milliliters is equal to1.057 quarts. Keep in mind that the pH scale islogarithmic, not linear. This means that if 10 dropsare required to lower the pH from 8.0 to 7.5, 20drops will not be required to lower the pH from 7.5to 7.0. Take considerable care to measure eachquantity of acid carefully and allow the pH to fullyequilibrate before making another addition.

General FertilityThere are two basic methods of meeting the

nutrient requirements of a soilless system.One is to purchase pre-mixed fertilizer formu-

lated by commercial companies. The other is topurchase the appropriate ingredients and mix yourown. As you will see as you read this information,it is usually much easier and less complicated topurchase a pre-mixed material. There are several onthe market that are available through variousgreenhouse suppliers. Pre-mixed soluble fertilizersusually contain a proper balance of both the macro-and micro-nutrients. Follow the manufacturer’sdirections for proper application.

A fertility program in a soilless system is oneof the more confusing and difficult aspects of pro-duction for greenhouse tomato growers. However, itis very important to success. The keys to a success-ful nutritional program include:1. Using fertilizer designed for greenhouse tomatoes.2. Knowing the amount of each fertilizer needed in

a stock solution.3. Knowing how to correctly make the fertilizer

application.4. Observing plants for signs of a deficiency or

excessive levels of a nutrient.5. Monitoring plant nutrient status by periodically

taking samples for tissue analysis. The tissuesamples must be sent to a private laboratory foranalysis.

6. Understanding the influence of light intensity onnutrient uptake and plant use and adjusting thefrequency of applications accordingly.

Fertility Measurement: Several units areused to express the fertility level of nutrientsolutions (fertilizer dissolved in water). This maybe confusing, since the use of different unitsmakes it difficult to understand different read-ings. This section helps to explain the differencesin these units.

Electrical conductivity (EC) is used to measurethe ability of a solution to conduct electricity. Themore electricity it will conduct, the higher the ECreading. The general unit used is mho (pronouncedMO), with the plural being mhos (pronouncedMOZE). Notice that mho spelled backwards is ohm(pronounced OM). Ohm is the unit of electricalresistance, while mho is the unit of conductivity.

Two units of mhos are commonly used:micromhos (umhos) and millimhos (mmhos). Amicromho is one-millionth of a mho; a millimho isone-thousandth of a mho. Another way of looking atit is that a millimho is 1,000 times bigger than amicromho. Either scale can be used. Convert frommicromhos to millimhos by sliding the decimalpoint 3 places to the left, and vice versa. Typicalreadings of micromhos are 0.30 to 2.50, whiletypical readings of millimhos are 300 to 2,500.Millimhos are more commonly used than micromhoson today’s EC meters. An illustration to make theconversion is provided below.

To convert millimhos to micromhos, multiplyby 1000. For example, a millimho reading of 1,000would be 1,000,000 micromhos (1,000 x 1,000 =1,000,000). To convert umhos to mmhos, divide by1,000. Thus, a micromho reading of 1000 is 1millimho (1,000 divided by 1,000 = 1).

Some portable EC meters measure the range ofelectrical conductivity from 0 to 30. These units aremicrosemens (us). They are simply 10 times thereading in millimhos. So to convert from us tommho, slide the decimal point one point to the left.For example, if the meter reads 15, it is 1.5 mmhos.All three of the above units are easily interchangedif necessary.

The most commonly used and easily under-stood method of expressing the nutrient status of anutrient solution is to use parts per million (ppm).Parts per million is the unit used to measure theconcentration of a specific nutrient in a solution.These units are usually within the range of 50 to300 ppm for nitrogen. General guidelines for the

17

ppm of nitrogen to use at different stages of growthare given in Table 7.

Another way of measuring the amount offertilizer in a solution is to measure the totaldissolved solids (TDS) as shown in column 3 ofTable 7. The unit commonly used for TDS is ppm. Ifyou know the ppm of each dissolved nutrient, addthem together to determine the total dissolvedsolids. This is a measure of all salts in a solution,not just nitrogen. However, TDS is not a reliablemeasurement of all nutrient levels. Some of thesalts could have been in the water before anyfertilizer was added. For example, if you had areading of 1,500 TDS, you do not know if thereading is due to nitrogen or some other nutrients.It could also have been due to sodium, or somethingelse, in the water. Thus, this is not a reliablemethod of measuring fertility of a nutrient solution.

It is important to know the dissolved solids orEC of the water source used to make the solution(do not assume it to be 0). Subtract the watersource EC or TDS measurement from that of thenutrient solution to find the true value of thenutrient solution.

Methods of Mixing andApplying Fertilizers

Two principal methods exist for mixing fertiliz-ers used in nutrient solutions: the bulk tank systemand the injector or proportioner system. Bothmethods are acceptable and can be adjusted to

maintain a good nutrient level that maximizes bothyields and quality of tomatoes.

Bulk Tanks: A bulk tank may be constructedof plastic, concrete, steel, PVC, etc. at the appropri-ate size for the greenhouse. Bulk tanks are usuallyused for self-mixed nutrients. A nutrient solution ofthe correct concentration for plants is mixed in thetank and pumped directly to the plants. A 100-gallon tank may be suitable for a single greenhouse,while a 1,000- or 2,000 gallon tank may be betteradapted to several greenhouses. The larger thetank, the less frequently fertilizer will have to bemixed. However, if it is too large, the fertilizer maysit too long between mixes, which may result in achange in the fertilizer concentration. If you areconsidering a bulk tank system, be sure to followthe fertilizer manufacturer’s directions for bestresults.

Mixing fertilizer is a matter of adding acertain quantity of a specific nutrient (pounds orounces) to a specific number of gallons of water. Anexample that illustrates this procedure is shown in“Mixing Your Own Nutrients,” which follows in thispublication. The fertilizer must be completelydissolved in water. Any material that settles outonto the bottom of the tank is not available forplant usage. If this happens, be sure to check thepH and bring it into the appropriate range or stirthe mix with a paddle. Do this each time a new mixis made.

Determining Bulk Tank Size: To determinethe size of bulk tank you need, you must know theflow rate per minute per 100 feet of irrigation

Table 7. Nutrient Concentrations Required for Greenhouse Tomatoes at Different Growth Stages

foegatShtworg htworg htworg htworg htworg

negortiN)mpp( )mpp( )mpp( )mpp( )mpp(

devlossidlatoT)mpp()SDT(sdilos )mpp()SDT(sdilos )mpp()SDT(sdilos )mpp()SDT(sdilos )mpp()SDT(sdilos

ytivitcudnocortcelE)CE( )CE( )CE( )CE( )CE(

)sohmm( )sohmm( )sohmm( )sohmm( )sohmm(

eurtts1otnoitanimreGdednapxeylluffael

05 055-054 6.0

dr3otfaeleurtts1dednapxeylluffaeleurt

57-05 006-055 7.0-6.0

gnitnalpsnartotfaeldr3 001-57008-006

9.0-7.0

otgnitnalpsnarTtesretsulcdn2

051-001 0531-0088.1-9.0

gnippototretsulcdn2002-051 0061-0531

2.2-8.1

18

tubing, the total number of feet in your green-house, the total minutes of run time and thenumber of applications per day. Then you willmultiply this by seven days per week. For ex-ample, if the flow rate is 0.33 gallons per minuteper 100 feet of tubing or tape at 8 psi, the totallength of irrigation tubing per house is 800 feet,the timer is set to run 15 minutes per run, appli-cation is made four times daily and is done foreach day of the week, then the gallons requiredare 0.33 x 8 x 15 x 4 x 7 = 1,108 gallons per week,or 158 gallons per day. This will provide an esti-mation of the size tank desired and the number oftimes per week that mixing must be done.

Injectors: A fertilizer injector is used to mixor proportion a concentrated nutrient solution, suchas a premixed fertilizer, into an existing flow ofwater moving to the root system. A concentratednutrient solution is usually withdrawn into thecarrier line from a container much smaller than thebulk container. An injector is usually placed aheadof the filtration unit in the line. There are severalinjectors on the market. Generally, the more youspend for an injector, the more accurate it will be inmixing the solution. The more accurate models aredose-specific, meaning that the concentrate injecteddepends on a given volume of water passingthrough the line. An injector that operates based onvolume is more accurate than one based on time.Injectors usually have a knob that can be adjustedto increase or decrease the dose of fertilizer concen-trate injected into the water.

The fertilizer solution flows from the concen-trate container (bucket or other container) to theinjector, where it is then diluted or mixed into theirrigation system. A water meter monitors the flowof water, and then sends a signal when enoughwater has passed through. The concentrate is heldin small volumes (10 to 50 gallons). A minimum oftwo heads and two concentrate tanks are necessary;one tank (B) is for calcium nitrate and the other(tank A) is for all other nutrients. Two tanks arenecessary because calcium will chemically combinewith phosphate when the two nutrients are in highconcentration, especially when the pH is high. Thetwo nutrients can react and form a very insolublecompound called calcium hydrogen phosphate,which can plug the injector and irrigation lines.Once diluted, there is no problem unless the waterpH is higher than 5.8. If this is the case, then youmay need to add a third head to inject acid. Acidinjection, however, must be done very carefully andslowly to avoid dropping the pH levels too low forgood solubility.

An injector system enables better control offertilizer applications than bulk tank systems,because the dose can be quickly adjusted. Asimprovements are made to the system, it is alsopossible to add an injector for each nutrient. Thiswill enable individual nutrient adjustment basedon normal tissue analysis. Computer systems maybe available to control this operation, but theycould be expensive.

Injector Calibration: It is important to knowthe injection ratio (ratio of the output to the input)so the amount of fertilizer to mix into the concen-trate tanks can be determined. Some injectorscome with tables that designate the ratio, i.e.,1:10, 1:15; 1:30, 1:100, 1:200, etc. If this informa-tion is not provided, then you must calibrate theinjector to find this number. Using a containerthat can provide an accurate measurement ofwater (graduated cylinder or beaker), measure theamount of water the injector sucks in one minute.Then, using several of the measuring containers,one at each of several emitters (if used) along theirrigation system, measure the amount of waterdelivered to the plants in one minute. Average thewater in all of the containers by dividing the totalvolume by the number of measuring containers.Multiply this average by the total number ofemitters in the greenhouse. Divide the totalamount emitted in the greenhouse by the totalamount the injector sucks in one minute. This isthe ratio. State it as 1:X, where X is the numberobtained after the above division. This means thatX parts of water are to be mixed with each part ofconcentrated nutrient solution.

Pre-Mix Fertilizers: Pre-mixed, water-solublematerials are available for use in soilless systems.They include products such as the general purpose20-20-20, 20-10-20, 15-11-29 and 5-11-26 “Hydro-Sol” with micronutrients. Follow the basic instruc-tions for using these materials, and you will findthat it is easier to use them rather than trying tomix your own in appropriate proportions. Thereasons for this become quite obvious when oneconsiders the complication in developing and main-taining a balanced mix. One example of a self-mixed process follows.

Mixing Your Own Nutrients: A self-mixedsolution is usually mixed in a bulk tank. Propermixing and maintaining a balanced nutrient solu-tion is complicated unless you are well versed infertilizer chemistry. One of the first steps in mixingyour own nutrient solution is knowing the concen-tration of each element in the solution. One of thebetter nutrient solutions that provides this informa-

19

lacimehCdnuopmoc

deilppuStneirtun

rofderiuqersmarGrepmpp1

).lag562(sretil000,1

)0-0-12(etaflusmuinommAnegortiN

rufluS67.422.3

)0-0-5.51(etartinmuiclaCnegortiN

muiclaC54.665.2

etartinmuissatoP)9.63-0-57.31(

negortiNmuissatoP

03.762.5

etartinmuidoS negortiN 54.6

)0-0-64(aerU negortiN 71.2

K,P,NelbulosretaW)51-54-9(

negortiNsurohpsohP

muissatoP

11.1122.266.6

etahpsohpmuissatoponoM)82-22-0(

muissatoPsurohpsohP

35.354.4

etaflusmuissatoP)81-3.34-0-0(

muissatoPruhpluS

13.25.5

edirolhcmuissatoP)8.94-0-0(

muissatoP 2

etahpsohpmuiclaconoM.aC31)0-8.02-0(

surohpsohPmuiclaC

87.496.7

etahpsohpmuinommaonoM)0-8.02-11(

surohpsohPnegortiN

87.490.9

)muspyg(etaflusmuiclaCmuiclaCrufluS

08.433.8

dicaciroB noroB 46.5

etaflusreppoCreppoC

rufluS19.318.7

etafluSsuorreFnorI

rufluS45.562.5

)%9(norIdetalehC norI 1.11

etaflusesenagnaMesenagnaM

rufluS50.498.6

etaflusmuisengaM)stlasmospE(

muisengaMrufluS

57.0196.7

)3OoM(edixoirtmunedbyloM munedbyloM 5.1

etadbylommuidoS munedbyloM 65.2

)edargtnegaer(etafluscniZcniZrufluS

87.262.5

Table 9. Calculation of Nutrient Solutions (Amount ofchemicals, in grams, used to make 1,000 liters (265 gal) ofnutrient solution.)

tion is the “Modified Steiner Solution.” Thevarious nutrients and their concentration inthis solution are shown in Table 8. One way touse a nutrient solution is to mix a solutioncontaining the concentration of each nutrientprovided, and then dilute the solution to pro-vide the concentration of nutrients necessary tofeed the plants.

Table 8. Modified Steiner Solution Illustratingthe PPM of Each Nutrient Required in theSolution

The next step in mixing a nutrient solutionis to know the ppm of each nutrient provided bya specific quantity of a material containing thenutrient. If you understand molecular formulas,you can figure this on your own. If you do not,then you could use the following table to deter-mine the quantity to mix with a given volumeof water. The calculation is based on the per-centage of nutrient contained in the compound.The concentration of each nutrient will beshown as the amount required to provide 1 ppmin 265 gallons of water (Table 9). This propor-tion is used because 265 gallons equals1,000,000 milliliters. Thus, if one gram or onemilliliter of the nutrient is mixed with thisquantity of water, then a concentration of 1 ppmexists for that specific nutrient.

If you mix the quantities of each of thefirst nutrient listed in each row in column 3 ofTable 9 into 265 gallons of water, you will have

htgnerts%001tanoitulosnimpP

171 )negortin(N

84 )surohpsohp(P

403 )muissatop(K

081 )muiclac(aC

84 )muisengam(gM

3 )nori(eF

2-1 )esenagnam(nM

1 )norob(B

4.0 )cniz(nZ

2.0 )reppoc(uC

1.0 )munebylom(oM

20

a solution that has the nutrient concentrations ofeach element provided in Table 10.

Table 10. Actual Concentration of Each Nutrient inSolution When the Quantities Given in Table 9 AreMixed

Nutrient PPMa

Nitrogen 6.52Calcium 4.20Potassium 7.87Phosphorus 7.98Sulfur 6.29Boron 1Copper 1Iron 2Manganese 1Magnesium 1Molybdenum 2Zinc 1

a.The ppm for each nutrient was determined by adding the

amount supplied by each of the compounds supplying

specific nutrients.

If you now compare the level of nutrientsnecessary from the Modified Steiner Solution(Table 8), you find that N, Ca, K, Fe and Mgrequirements are low, while Cu, Mo and Zn levelsare too high. Thus, further mixing is required toprovide the concentrations specified in the Modi-fied Steiner Solution.

Meeting calcium requirements: To meet theappropriate requirements, other mixing must bedone. We will start with calcium. We need to add175.80 ppm (180 ppm needed-4.20 ppm provided inthe solution = 175.80 ppm.) We will use calciumnitrate as the base material. It contains 19 percentcalcium. Thus, 5.26 grams of calcium nitrate willbe required to provide 1 ppm of calcium. Multiply-ing 175.80 x 5.26 = 924.7 grams (32 ounces) ofcalcium nitrate required.

Meeting nitrogen requirements: The cal-cium nitrate mixed above will also provide nitro-gen. For each 5.26 grams of calcium nitrate added,the concentration of N will increase by 0.82 ppm.Thus, 924.7/5.26=175.80 x 0.82=144.2 ppm Nsupplied. We need 171 ppm. Thus, 144.2 +6.52=150.72 total ppm N provided. We have 20.3ppm (171-151.82) to make up. To accomplish, wewill use only a nitrogen-supplying material suchas urea. Checking Table 9, we find that 2.17 gramsof urea will provide 1 ppm N. Thus, 2.17 x 20.3 =44 grams of urea are required to meet all of thenitrogen requirements.

Meeting phosphorus requirements: We have7.98 ppm of the total requirement of 48. To meet theshortage, we will need to provide another 40.02 ppmof P. Monopotassium phosphate provides 1.26 ppm ofP for each 3.53 grams added. Adding 31.8 grams(40.02/1.26) will provide the amount of P necessary.

Meeting potassium requirements: Each 3.53grams of monopotassium phosphate also supplies 1ppm of K. Thus, another 9.00 ppm of K frommonopotassium phosphate has been added for a totalof 16.87 ppm. To bring the K up to the desired levelwill require another 287.13 ppm. To meet this require-ment, there is a choice of potassium sulfate or potas-sium chloride or a combination of both. We will choosepotassium sulfate. Each 2.31 grams will provide 1ppm K. Thus, 287.13 x 2.31 = 663.27 grams or 1.5pounds. This material will also add another 121 ppmof sulfur, for a total sulfur concentration of 127.3 ppm.There is none provided in the Steiner Solution.

Meeting minor element requirements: Tomeet the copper, iron and molybdenum require-ments, add only 0.78 grams of copper sulfate, 16.6grams of ferrous sulfate and 0.5 gram of sodiummolybdate to provide the concentration specified inTable 8.

Using the nutrient solution: Now that wehave gone through the process of mixing a nutri-ent solution, how can it best be used to fertilizetomatoes? It was mentioned in Table 7 thatgreenhouse tomato fertilizer programs use nitro-gen as the guide for fertilization, even thoughother elements are provided in the ModifiedSteiner Solution. Table 7 indicates that tomatoesneed 50 to 75 ppm N from the first true leaf untilthe third leaf is fully expanded. The solution thatwe have just mixed provides 171 ppm N. Eachgallon of the solution must be further diluted toprovide the appropriate levels at this growthstage. To determine the gallons of nutrient mix towater, divide 171 by either 50 or 75, dependingon the level you intend to feed. Thus, 171 dividedby 75 equals 2.28 gallons. Dividing 171 by 50equals 3.42. This means that each gallon ofsolution will require that 2.28 to 3.42 gallons ofwater be mixed with it to place the nitrogen inthe required range. By making this dilution, allother nutrients in the mix will also be diluted inthe same proportion. As the plant grows into theother stages, the dilution rate will be adjustedaccordingly.

From these calculations, you can see that thepurchase of a pre-formulated material is much easier.

21

Identifying Nutr itionalProblems

High Nitrogen: Learn to monitor the plantsvisually to determine if there is a potentialnutrient problem. The most common nutrientproblem occurring with soilless greenhouse toma-toes is high nitrogen. Symptoms of high nitrogenare given below.

Excessive nitrogen can result in fairly seriousproblems in greenhouse tomatoes by shifting theplant into a vegetative plant. How do you know ifyou are over-applying nitrogen? There are severalsymptoms, which include:1. “Balling up” of leaves in the top of plants. This

term refers to the curling under of the smallleaves in the terminals.

2. The midrib of leaves tends not to grow in astraight line. It will grow in a curved manner,resulting in growth to one side of the leaf.

3. Small, vegetative growth will emerge from thetop of the leaf midrib.

4. Shoots of vegetative growth will grow at theends of flower clusters. These can be removed.

5. Fruit set will usually be decreased, with one ortwo fruit per cluster instead of four or five.Usually, these occur on three or four clusters andwill disappear when the nitrogen levels havedecreased. In terms of pounds, this could result in11/2 to 21/2 pounds of fruit loss per plant.

6. Leaf growth will increase in size and will bedark green.

Nitrogen deficiency: A deficiency results inrestricted growth of tops, roots and lateral shoots.Plants become spindly, with a general yellowing ofthe entire plant. Plants will turn to a light green,with increasing intensification of yellow. The olderleaves yellow first, then yellowing proceeds towardthe younger leaves. Older leaves also defoliate early.

Phosphorus deficiency: The leaf color isusually a bluish-green; the petioles and veins of theundersides of the leaves become purple. Young leafveins turn dark purple.

Potassium deficiency: Mature, lower leavesfirst show marginal yellowing, followed bydessication (burning) of the tissue along the margins.The symptoms progress both inward on the leaf andupward on the plant as the deficiency becomes moresevere. The fruit will often ripen unevenly or willshow blotchy green to yellow patches.

Calcium deficiency: The most common foliarsymptom is the scorching of new leaf tips and die-

back of the growing points, but the best known andmost identifiable symptom is blossom end-rot of thefruit. Boron deficiency also causes scorching of newleaf tips and die-back of growing points. However,calcium deficiency does not promote the growth oflateral shoots and short internodes as does borondeficiency, and boron deficiency does not causeblossom-end-rot.

Magnesium deficiency: Magnesium defi-ciency is most commonly characterized byinterveinal chlorosis (yellowing between the veins),which starts in the older leaves and proceedstoward the younger leaves as the deficiency be-comes more severe.

Sulfur deficiency: Sulfur deficiency re-sembles nitrogen deficiency in that older leavesbecome yellowish-green and stems become thin,hard and woody. Some plants may show a colorfulorange and red tint rather than yellowing. Thestems, though hard and woody, increase in lengthbut not in diameter.

Iron (Fe) deficiency: Iron deficiency usuallystarts as a yellowing of the immature leaves andgrowing points. As it progresses, this tissue mayturn almost white.

Manganese (Mn) deficiency: Manganesedeficiency starts with interveinal chlorotic mottlingof the immature leaves. In many plants, it isindistinguishable from iron deficiency. As thedeficiency becomes more noticeable, necrotic spotsusually appear in the interveinal tissue. Sometimesbloom buds on the flowering clusters show incom-plete growth and do not develop. During the shortdays of December and January, the plants oftenproduce no blooms at all.

Zinc (Zn) deficiency: Symptoms are verysimilar to iron and manganese deficiency, exceptthat small leaves result. When zinc deficiency issudden, such as when zinc is left out of the nutrientsolution, the chlorosis can appear similar to ironand manganese deficiency without the small leaf.

Boron deficiency: Symptoms include slightchloris to brown or black die-back of the growingpoints similar to calcium deficiency. The die-backtissue is usually very dry, brittle and easilycrumbled. The pith of affected stems may behollow, and the epidermis becomes roughened andcracked. Plants may also have short internodeswith prolific lateral shoot development on midribsof the leaves and the flower clusters. The mildestsymptom shown on mature fruit is very smallcracks to heavier concentric cracking in the skinon the shoulders.

22

Copper deficiency: With copper deficiency,leaves at the top of the plant wilt easily. This isusually followed by chlorotic and necrotic areas inthe leaves. Leaves on top of the plant show unusualpuckering with veinal chlorosis. Splitting of ripefruit, especially under warm temperatures, is anindication of low copper.

Molybdenum deficiency: The older leavesshow interveinal chlorotic blotches, andbecome cupped and thickened. This deficiencyis very seldom seen in greenhouse tomatoes.

In addition to the above deficiencysymptoms, a deficiency of one micronutrientcan result from an excess of another. Thus,the importance of maintaining a nutrientbalance cannot be overemphasized. Tempera-ture and pH can affect nutrient solubility andconcentration. Recycling nutrient solutions cancreate an imbalance in the stock nutrient solution.

Trellising orProviding Suppor ts

Tomato plants must be supported, regardless ofthe growing system. In soil systems, they can eitherbe staked individually or the “Florida Weave”system can be installed. The “Florida Weave” ismost commonly used and is illustrated in Figure 4.

Figure 4. Illustration of supporting tomatoes grownin soil using a “Florida Weave.”

With the “Florida Weave System,” two plantsare spaced between stakes and supported by nylonstring tightly connected to both sides of the stakesand running parallel to the soil surface, at aboutthe 12-inch height. Strings are then repeated aboutevery 8 inches until supporting is complete.

Soilless systems use a different support system.These systems drop strings from overhead pipe

supports tied to a rigid plastic ring at the base ofeach plant. The plants are then supported by thestring through repeated connections of plastic ringsabout every 8 or 10 inches up the plant. The systemis illustrated in Figure 5.

Maintaining support, regardless of the systemused, requires daily observation and labor.

PruningA sucker is new growth that occurs between

the axis of the leaf and stem. There will usuallybe one sucker at the axis of every leaf. If suckersare allowed to grow, they will also producesuckers. Suckers produce both foliage and fruit.If not removed, they will produce more foliagethan the root system can adequately support andprovide additional material to harbor disease andinsect organisms.

The enclosed environment and close plantspacing of greenhouse tomatoes make it necessaryto remove a high percentage of the sucker growth.The severity of pruning may be dependent on themethod of production and the variety or cultivarused. Growers using determinate varieties in soilsystems may not prune, while growers using inde-terminate varieties in hydroponic systems over along period may prune extensively. If suckering is

Growing trough

String

Pipe supports

Ring

Figure 5. Providing tomato plant support inhydroponic systems through the use of overheadsupports and drop-string.

nylon twine - 2 layers(one on each side of stake)at same location

8˝

8˝

12˝

23

done, begin the process when the first suckers areabout 2 inches long and continue thereafter as newsuckers reach that length. If the suckers becomemuch longer, they are difficult to remove withoutleaving a wound on the stem. Wounds becomepoints of entry for fungal organisms, which aremajor problems as greenhouse humidity increases.

Usually, a plant can be pruned to a two-stemsystem, although soilless systems are normallypruned to one stem. One-stem plants are desirablewhen close spacings are used, but are less necessarywith wider spacings. To develop the two stems,allow the main stem to grow, then allow the firstsucker underneath the first flower cluster to grow.Keep all others removed. This will form a two-stemsystem and will increase the chances of higheryields. The idea is presented in Figure 6.

Figure 6. Illustration of suckering or pruningtomatoes.

Weed ControlWeed control in a soil system is very much

like cultivation in the field, because there are noherbicides labeled for greenhouse use. However,fumigation will reduce the requirement for weedcontrol. Cultivation can begin when weeds andgrasses are very small, and should be done asshallow as possible to reduce root damage. Cultiva-tion is usually accomplished by running a roto tillerbetween the rows.

Some growers have tried production on plasticfor weed control, earlier yields and higher qualityfruit. If you use plastic, remember to install atrickle or drip tape underneath so water can beapplied as necessary.

Organic mulch materials have been used toreduce weed growth, but they also serve to keephumidity high and may serve as a habitat for bothfungi and insects. These are all very undesirable inthe greenhouse and should be kept to a minimum.

Soilless systems normally do not require weedcontrol programs because the system itself usuallyprevents weed growth.

IrrigationSoil Systems: Tomatoes grown in soil culture

should be irrigated so water is delivered to the baseof the plant rather than through overhead sprinklersystems. This keeps water off the foliage andreduces the potential for fungal diseases such asbotrytis or leaf mold, which can devastate cropyields. Greenhouse tomato growers have improvedtheir yield per plant by shifting from sprinkler totrickle irrigation.

Water application at the base of the plant insoil systems also reduces greenhouse humidity andweed growth between rows. Systems can be de-signed with a minimum of one plastic line per row;however, some growers use a line on each side ofthe row. Each line is designed to operate at eight to10 pounds pressure.

The trickle tubing can be purchased withmany options, but a good rule of thumb is to usetubing with a flow rate of 0.3 to 0.4 gallons perminute per 100 feet of tubing at an in-line pressureof 8 psi. In a soil system with eight rows of 90-feetlength, it requires a water flow of 2.16 to 2.9gallons per minute to meet the total water require-ment. To apply enough water to wet the root zonewill require 450 gallons of water applied in a 1-footband to be equivalent to 1-acre inch. To apply thisamount will require about 2.6 (155 minutes) to 3.5hours (210 minutes) run time.

The frequency of application will vary with therate of drying and water use. To reduce the poten-tial for inadequate water, monitor the soil andapply water frequently enough to keep the root zonemoist. This assures that adequate quantities ofwater are available to maintain maximum fruit setand size but reduces the potential for high humiditybuild-up within the greenhouse. It is important tokeep the soil in the root zone moist because, oncedry, it may be very difficult to bring it back to therequired level.

The components of a drip irrigation systeminclude a fertilizer injector, filtration units, pressure

First flower clusterLeave this suckerto form atwo-stem system

Suckers

24

10. Mainline11. Submain Secondary Filter (only if required)12. Field Control Valves (Manual or Automatic)13. Laterals

1. Pump2. Pressure Relief Valve3. Air Vents (at all high points)4. Check Valve5. Fertilizer Injector or Tank6. Mainline Valve (Gate or Butterfly Valve)7. Pressure Gauges8. Filter9. Flowmeter

Figure 7. Schematic of a drip irrigation system for soil production system.

regulators, drip tape, supply lines and variousconnectors, seals and plugs or clamps. An illustra-tion of a suitable system and its components areshown in Figure 7.

Hydroponic Systems: Usually, water andfertilizer are applied simultaneously to the rootsthrough the plumbing system installed in thegrowing trays, troughs or bags.

Light RequirementsBest fruit set and plant growth occur when

tomatoes are grown under full sunlight or maxi-mum light intensity. This helps to explain whyspring yields are usually higher per plant than fallyields. Light intensity in the spring is much greaterthan in the fall.

Supplemental fluorescent lighting has notproven to be worth the cost of installation. There-fore, most greenhouse growers in Tennessee do notuse supplemental lighting.

25

Carbon DioxideEnr ichment

In areas where several days may pass withoutventilation, carbon dioxide enrichment up to 10times normal results in increased yields. However,if growth occurs at a time when ventilation can beadequately provided, carbon dioxide enrichmentusually does not prove to be economically feasible.

Ventilationand Humidity

Air movement through the greenhouse isimportant to improve pollination and reducediseases enhanced by high humidity. The idealhumidity level for greenhouse tomatoes is between60 and 70 percent.

On rainy days, the above humidity levels willbe difficult to obtain by ventilation, but a green-house should not be kept totally closed on sunny,cool days. When the air is cool and dry, ventilationwill enable air to be pulled through the house andreduce internal humidity if it is kept above theplants. If cool air is drawn into the house andwarmed up, it will hold greater moisture at thehigher temperature. Complete exchange of air inthis manner helps reduce problems. Since green-house growers have improved their ventilationsystems compared to those used in the early ‘80s,crop yields have increased and foliar disease prob-lems have decreased.

A good ventilation system has the capability tochange the air once per minute, even though therewill be times when cold outside temperatures willnot allow an exchange this rapidly. When moisturecondenses on the internal plastic surface, ventilatethe house and continue as long as the internaltemperature does not become too cool, or as long asthe moisture on the plastic surface is being re-moved. Keep ventilation in accordance with theexternal temperature, because air that is too cooldrawn continuously over the foliage will reduceplant growth. Do not allow too cool air to makecontact with the plants and do not ventilate thehouse long enough to reduce the internal tempera-tures to undesirable levels.

Management of ventilation is of major impor-tance. Avoid keeping the house closed on days whenthe outside temperature will allow maximumventilation. If this happens, humidity and tempera-

ture both increase to unfavorable levels, increasingconditions favorable for disease development. Inaddition, learn to use intermittent ventilation oncool days to reduce moisture condensation inside thehouse. The drier the foliage can be kept and themore air movement in the greenhouse, the morefavorable the conditions for pollination.

Growers who have previously had low ventila-tion capability have doubled their yields of springtomatoes in several situations when they replacedold houses and increased their ventilation capability.

PollinationIf flowers are not too wet due to high humid-

ity in the greenhouse, they will shed pollen satis-factorily, resulting in good fruit set. However,pollen grains that are too wet become sticky anddo not shed from the stamen for transfer to thepistil very well. Good air movement can provideeffective pollination on a spring crop, but is moredifficult to achieve on a fall crop due to decreasingoutdoor temperatures.

In addition to good ventilation, many green-house growers are now providing one hive ofbumblebees per greenhouse per crop to assurebetter pollination. The cost of each hive is about$200 at the time of this printing.

When good ventilation does not occur and ifbumblebees do not do the job, each flower clusterwill need to be vibrated every other day until fruitset is accomplished. The best time to hand polli-nate is between 10:00 a.m. and 2:00 p.m. duringthe drier portion of the day. Electric toothbrushesor any hand-held rapidly vibrating device willcontribute to increased pollination. Using suchdevices, however, requires considerable time tocomplete pollination as frequently as required,causing an added production expense.

DiseasesTomatoes grown in soil culture are subject to

nematodes, fusarium and verticillium wilt,botrytis, leaf mold, early and late blight, foliar andfruit bacterial problems and viruses. These canoccur as a single problem or a combination of twoor more at a time. Total or marketable yields canbe reduced by 10 to 80 percent, depending on theseverity of one or a combination of these diseases.A description of several diseases is provided inTable 11.

26

The importance of good sanitation, preventa-tive and ventilation practices cannot be overemphasized, because the array of chemical controlslabeled for greenhouse production is much morelimited than for field tomatoes. Also, the necessaryspray program must be accomplished with eitherhand equipment or small, walk-type motorized

sprayers. Because application with hand equipmentis not uniform, chemicals provide less control thanthe same material applied with better equipmentin the field.

Diseases affecting tomatoes grown in soillessculture include various root bacteria, leaf mold,botrytis and viruses. The total number of diseases

Table 11: Description of Greenhouse Tomato Diseases

esaesiD noitpircseD

stopslairetcaB.kcalbotnworbyllausuerayehT.tiurfnostopsdesiar,llamS

.tiurfehtfoecafrusehtnotopsetihwasireknaclairetcaB

thgilbylraE

foecneserpehtybdeifitnedisitI.sesuohliosnimelborpAekil-tegratotnipolevedhcihwstopskcalb-ot-nworb,llams

yehT.tsrifsevaelrewolehtnoraeppastopsehT.stops.tiurfehtfodnemetsehtnotopsyrehtael,kradasaraeppa

tliwmuirasuFlacipyT.sesuohsselliosnimelborpaebotylekiltoN

metS.egailofehtfognitliwdnagniwolleyaedulcnismotpmys.skaertsnworbwohsotylekilsienildnuorgehtraeneussit

)sityrtob(dlomyarG

yllaususitI.sesuohsselliosdnalioshtobninommocyreVrewolfrosmetsehtnohtworgyarg,yzzufaybdezingocer

dnapitehttagninnigebnworbnrutsevaelehT.slecidepehtnehwmelborprojamasemocebtI.drawkcabssergorp

tpekylsuounitnocsiytidimuhehtdnadetalitnevtonsiesuoh.slevelhgihta

dlomfaeL

-ralucric,wolleyedulcnismotpmyS.dlomyargnahttnereffiDoteviloerastopS.sevaelfoecafrusreppuehtnostopsekil

nehwsmetsyshtobniruccO.sevaelfoedisrednuehtnoyarg.levelhgihatayltnatsnoctpeksiytidimuheht

)tonktoor(yrujniedotameN

suounitnocerehwsesuohliosnidnuofebotylekilsIsdoirepgnirudyldipartliwlliwstnalP.derruccosahnoitcudorp

otraeppayamdnawolleynrutsevaeL.ssertserutsiomfoehtdnadetnutsemocebstnalP.ycneicifedtneirtunaevah

.stonkrosllagpolevedstoor

surivciasomoccaboT

saeraneergkraddesiarhtiw,gnilttomedulcnismotpmysfaeLsmotpmysereveS.sevaelregnuoyfonoitrotsidemosdna,hguoremoceb,drawnwodnrutyamhcihwsevaeledulcni

ehttadrawnwodlrucyamdna,detagurrocrodelknirc.detnutsemocebyamstnalP.snigram

thgilbnrehtuoS

yreveiddnatliwstnalP.esuohliosanimelborpafoeromsImetsehT.egailofehtfogniwolleyevitcnitsidatuohtiwyldiparahtiwderevocdnadeyacedebyllausulliwenildnuorgehtta

.seidobgnitiurfnworb-thgilllamsdnadlometihw

tliwmuillicitreV

wolleylliwegailofehT.smetsyssselliosniruccootylekiltoNlanretnI.sevaelehtnosnoiseldepahsvsmroftI.tliwdna

nworbwohsyllausulliwtnalpehtfoesabehtraeneussit.noitarolocsid

27

in soilless culture may not be as great as with soilculture, but the magnitude of their effects are noless important. They can still be devastating.

When fungicides are available and used, theyshould be handled and applied as indicated by thelabel. Every effort should be made to apply them toboth sides of the leaves as well as stems and flowerpeduncles. Fungicides available for greenhousetomato use are listed in Extension PB1282, “Com-mercial Vegetable Disease, Insect and WeedControl,” available at your county Extension office.This publication is updated annually.

Fruit Physiological DisordersThere are several physiological disorders which

can occur in greenhouse tomatoes. Descriptions ofsome of the more common disorders follow.

Blossom-end-rot (BER): This disorder appearson the blossom end of the fruit, usually after thefruit is three-fourths to full size. It appears as alight tan, brown or black sunken area. It is not asoft rot, but is a firm, somewhat leathery conditionaccompanied by a dry rot. The disorder may not beany more than 1/8 inch deep into the outer carpelwall of the fruit.

BER is caused by a calcium deficiency. It canoccur when adequate calcium is present, butconditions exist which reduce its uptake such as aninsufficient amount of water in the root zone.Other causes include improper pH or wide rangesin certain fertilizer salts in the root zone. Forexample, it is possible to have an ammonicalnitrogen-induced calcium deficiency because theammoniated nitrogen levels in the root zone arehigh enough that it is substituted for calciumduring uptake. To prevent BER, maintain adequatelevels of calcium and prevent wide fluctuations inwater levels in the root zone.

Puffiness: Puffy fruit have an angular appear-ance, with one or more sides becoming flattened. Insome cases, fruit may appear to be triangular ratherthan round. Such fruit weigh less than non-puffyfruit and the locules are not well filled with bothseed and gel. Some locules may even be empty.

Puffiness has been associated with poor polli-nation and several of the following environmentalconditions:1. High temperatures, especially consecutive tem-

peratures above 90 degrees during flower develop-ment.

2. Temperatures below 55 degrees during flowerdevelopment.

3. Wide differences between day and night temperatures.4. Water stress: both too much and too little. This

could include high humidity that reduces pollenshed.

5. Excessive nitrogen.6. Use of fruit-set hormones.7. Lack of adequate carbon dioxide.

The best way to cure puffy fruit is to preventit from occurring by monitoring the environmentalconditions which favor its development. If puffinessoccurs on early-set fruit and it can be associatedwith any of the above conditions, then adjust theconditions as close to normal as possible to reducethe potential for problems in later-set fruit. Ifconditions exist that result in poor pollination,correct them as soon as possible.

Fruit Cracking: This is one of the moreserious problems with greenhouse tomatoes. Cracksradiating from the stem are the most prevalent, butsome concentric cracking also occurs. Like blossom-end-rot, cracking is associated with water stresseswithin the plant. Fluctuating water levels withinthe root system may increase the incidence ofcracked fruit. Cracking has also been associatedwith genetics of the plant. As a result, some recentvarieties have been evaluated for crack resistance.When possible, use crack-resistant varieties.

Other information indicates that fruit crackingoccurs when high levels of nitrogen are present inthe leaf tissue. In addition, low potassium levelsseem to increase the number of cracked fruit.

Rough or Catfaced Fruit: This problem hasbeen clearly shown to be associated with low tem-peratures during flower bud development. Green-houses which have uneven temperatures due to coldspots or sloping elevation that favors colder tempera-tures at the lower levels will usually have a highpercentage of catfaced fruit produced at the lowerlevels. The shoulders of large- fruited varietiesusually are rougher than smaller-fruited varieties.

Blotchy Ripening: This problem appears as aflattened, blotchy, brownish-gray area on greenfruit. As the fruit ripens, these areas may remaingray or turn yellow. Dark brown vascular tissuecan be seen in the fruit walls when the fruit is cut.Determining the cause of the problem can bedifficult. It may be a result of the many environ-mental problems already mentioned. In addition,the development of red fruit color is inhibited whentemperatures move above 86 degrees during fruitdevelopment.

Zipper or Anther Scar: This vertical scaralong the side of the fruit resembles a zipper, or

28

perhaps the type of scar left by stitches. It is causedby the anther sticking to the edge of the ovary(immature fruit). The anther appears to adhere to ahigher percentage of the fruit when the greenhousehumidity is excessive, increasing the stickiness ofthe anther to the fruit. As the fruit increases insize, the anther tears away from the fruit, leavingthe scar.

Green Shoulders: This condition occurs at thecalyx or stem end of the fruit, which never turnsred. Often, the area may turn yellow as the remain-der of the fruit ripens. It has been associated withgenetics, but is usually more prominent during highlight and temperature conditions. Recommendedconditions to reduce the problem include increasingventilation during warm periods, being sure thatplants are not defoliated above the developingclusters, using shade materials and good P and Kfertility levels. In addition, some varieties havebeen released, especially among field tomatoes, withresistance to this problem.

InsectsDo not think that tomatoes grown in enclosed

structures are free of insects. They are subject toinfestation by aphids, flea beetles, fruit worms, whiteflies, mites, leaf miners, pinworms and others. Adescription of these insects is provided in Table 12.

The first step in insect control is eliminatingoverwintering and colonizing habitats suitable forinsect survival. This means that plant residueshould be completely removed from within or nearan existing house. Installing screens over fanskeeps many insects from entering through the fans.The second step is identifying the insect and apply-ing the recommended control if one exists. Unfortu-nately, just as with diseases, control chemicals forgreenhouses are limited. Sticky tape and certainsynthetic pyrethroids are available for use ingreenhouses. They are very helpful in early identifi-cation of insect problems and in keeping manyinsect problems to a minimum. Proper use ofcontrol techniques and sanitation measures cankeep insects under control much more satisfactorilythan problems with diseases. However, remember tobegin control programs before plants are trans-planted to the greenhouse for best results.

HarvestingHarvest tomatoes for shipment when the star

on the blossom end turns pink. Fruit harvested atthis time is red internally and will turn redwithout treatment with ethylene. Such fruit,however, must be packaged and moved to themarket immediately for it to be a proper colorwhen placed on the grocery shelf. Mature greentomatoes can be harvested and treated with ethyl-ene (ripening gas) under appropriate conditions todevelop color. Green fruit are usually harvestedless frequently than ripe fruit. Tomatoes that areto be sold locally and used immediately can beharvested when vine-ripe.

Sorting and PackingTomato fruit should be sorted by size and

color to have a uniform pack suitable for variousmarkets. Only one size and color should be placedin a box. This allows buyers to know what theyare purchasing and improves a grower's reputa-tion for packing a high-quality product. Suchtechniques bring repeat buyers. If tomatoes aregoing into chain store outlets, package them in20- or 25-pound cardboard boxes and stamp themas to size, color and brand. This provides a buyerwith both good handling and identification capa-bilities. Tomatoes that are sold locally throughvarious private market outlets are often packagedin one-half to one-bushel crates and sold in theearly-pink stage.

StorageKeep green tomatoes above 55F until they

have ripened. If they are stored at temperaturesbelow 55F while green, the low temperature deacti-vates the enzyme responsible for color development.The salability of the product and reputation of thegrower are then reduced.

After ripening, tomatoes can be kept five to 10degrees cooler than mentioned above, but thehumidity must be high to keep the fruit fromswiveling due to water loss.

29

Table 12. Description of Insects Commonly Found Feeding on Greenhouse Tomatoes

tcesnI noitpircseD

sdihpA

foriapahtiwstcesnidepahs-raep,deidob-tfos,llamSraerehtmorfgnidurtorp)snoitcejorpekil-epipliat(selcinrocdegniwebyamyehT.neergrokcalb,derebyamyehT.dne

.sevaeldnaslanimretnoseinolocnideefdnasselgniwrosdihpA.detrotsidemocebdnalrucnetfosevaeldetsefnI

.sesaesidsurivtimsnart

selteebaelF

yehT.saelfekilpmujtahtselteebdepirtsrokcalb)61/1(llamSsiegamaD.seloh-tohsdnuor,llamsgnivael,egailofehtkcatta

yamselteebaelfotatoP.nosaesehtniylraesuoirestsom.thgilbylraetimsnart

smrowtiurF

morfrolocniyraveavraL.evilo-hsiwolleyerashtomtludArelaphtiwkcalbneveronworbhsidder,wolley-hsineerg

deefsmrowtiurF.ydobehtgnolaesiwhtgnelgninnursepirts.klatsehtotnierobyamdnatiurfdnasevaelehtno

srenimfaeLyehT.htgnelnihcni8/1tuobadnawolleyeraeavralehT

sihT.secafrusrewoldnareppuehtneewtebsevaelehtlennut.sevaelehtnoslennutgnidniw,etihw,gnolnistluseregamad

smrownipotamoT

ehT.hcni2/1fonapsgniwahtiwyargsihtomtludaehTderevocdnayarghsaroneerg,wolleyebyameavralerutam

faelhsitihwesuacnacsmrowniP.stopselprupkradhtiwtiurfdnasmetsniselohnip,sevaeldeitdnadedlof,skaerts

.sehctolbtiurfdna

setimredipS

ehteratahtstsepekilredipsneergkradothsiwolley,llamSgnigdolsidybdetcetedebyamyehT.sekalfreppepfoezisgniweivdnarepapetihwfoeceipaotnotnalpehtmorfmeht

revoneesebyamgnibbeW.snelgniyfingamX01ahtiwmehtsevaeL.egailofmorfpasehtkcussetiM.stnalpdetsefnieht

.tsaceznorbrohsiwolleyarehtienoekat

seilfetihW

niyravyamyehT.seilfetihwfoseicepslareveseraerehT,revewoH.epahsgniwsahcus,epahsydobfostcepsaniatrec

,enifhtiwderevocsgniwdaorbhtiwstcesnillamsllaerayehtdeefyamshpmyndnastludahtoB.redwopyxawetihw-wons

.faelehtfoedisrednuehtmorfseciujgnikcusybegailofnogninekcalbanitluseryamhcihwwedyenohaecudorpyehT

gnittimsnartfoelbapacoslaeraseicepsemoS.faelehtfo.tnalpehtegamadyltaerghcihw,sesurivniatrec

30

PB1609-2M-4/98 E12-2015-00-201-98

Other References of Interest1. HortTech 6:(3)1996. Vegetable Production Using Plasticulture.

2. Lamont, William J. Jr, and Charles Marr. Greenhouse Vegetable Production: Hydroponic Systems. Coop-erative Extension Service. Kansas State University. Manhattan, Kansas

3. MSU Ag Facts. Extension Bulletin E-1736, September, 1983. Greenhouse Growth media: Testing andNutrition Guidelines.

4. Snyder, Richard. Bulletin 1003, October, 1993. A Spreadsheet Approach to Fertilization Management forGreenhouse Tomatoes. Mississippi Agricultural and Forestry Experiment Station.

5. Snyder, Richard. Pub. 1828. Greenhouse Tomatoes. Cooperative Extension Service. Mississippi State Uni-versity.

6. SB-19. Growing Greenhouse Tomatoes in Ohio. Cooperative Extension Service. The Ohio State University.

7. Wittwer, S.H., and S. Honma. Greenhouse Tomatoes. Michigan State University Press. East Lansing. 1969.

A State Partner in the Cooperative Extension SystemThe Agricultural Extension Service offers its programs to all eligible persons

regardless of race, color, national origin, sex or disability and is an Equal Opportunity Employer.COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS The University of Tennessee Institute of Agriculture, U.S. Department of Agriculture,

and county governments cooperating in furtherance of Acts of May 8 and June 30, 1914. Agricultural Extension Service

Billy G. Hicks, Dean