alabama a&m and auburn universities guide to commercial staked tomato production in ... ·...

ANR-1156

A L A B A M A A & M A N D A U B U R N U N I V E R S I T I E S

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Historical PerspectiveThe tomato (Lycopersicon es-

culentum Mill.) is a member ofthe Solanaceae family (Night-shade family), which also con-tains bell peppers, hot peppers,eggplants, and Irish potatoes.The tomato is the most com-monly cultivated vegetable cropin the world.

A native of the tropical re-gions of South America, thetomato was spread by ancientpeoples along trade routes. Thetomato was a staple in theirdiets. In the seventeenth centuryas the Spanish began exploringthe New World, they collectedplants; however, the tomato didnot become widely used in thediets of most Europeans until themid-eighteenth century. After thetomato gained in popularity foruse in cooking, it quickly foundits way to the United States.

Today the United States pro-duces more fresh market toma-toes than any other country inthe world produces. In 1998,Alabama ranked twelfth follow-ing California and Florida asleaders in fresh market produc-tion in the United States.

The production of stakedtomatoes is highly specialized(Figures 1a and 1b). It is laborintensive, requires a high initialinvestment, and demands a highlevel of management to be prof-itable. Staked tomato productionshould only be considered if youplan to do a thorough and con-scientious job of managing youroperation.

PlantingRecommendationsPlanting Dates

Tomatoes are a warm-seasoncrop sensitive to cool weather.This limits the use of direct seed-ing as a means of production inAlabama. Transplanting is thepreferred method of production.When transplanting, it is best towait until after all threats of frost

have passed before planting.Depending on which stage ofmaturity is desired (mature greenor breaker stage), most tomatovarieties require 35 to 60 daysfrom transplanting to reachingmarket maturity. Transplants aregenerally set around March 10 insouthern Alabama, April 1 incentral Alabama, and April 15 innorthern Alabama.

Soil and FertilityTomatoes can be successfully

grown in most soils in Alabama.A well-drained, sandy loam,loam, or clay loam with a pH of6.0 to 6.8 is preferred. Using acover crop plowed in a monthor more before transplanting canbe beneficial by increasing theorganic matter composition ofthe soil and by providing an ad-ditional source of plant nutrients(especially if the cover crop is alegume). Subsoiling may bevaluable on soils with plow pansor hardpans.

Avoid continual cropping oftomatoes, peppers, eggplant,Irish potatoes, or any relatedvegetable crop on the same landarea. Rotating tomatoes withnonrelated crops every 2 to 3years is essential; crop rotation isa basic and effective means ofcontrolling soilborne diseasesand nematodes that otherwisemay not have an effective chem-ical control. It is also importantto avoid areas with known prob-lems such as southern blight,heavy weed infestations, poordrainage, or steep slopes.

Guide to Commercial Staked Tomato Production in Alabama

Figure 1a. Spring/early summer pro-duction of staked tomatoes on blackplastic with drip irrigation

Figure 1b. Summer/fall production ofstaked tomatoes on white plastic withdrip irrigation

2 Alabama Cooperative Extension System

Tomatoes are heavy feeders.To assure a good response tofertilizers, a detailed soil analysisfor each field is important.Planning a fertilizer programbased on soil test results helpsyou to satisfy the nutritional re-quirements for the tomatoes.Timely and appropriate applica-tion of fertilizer will make a criti-cal difference in the quality ofthe crop as well as the overallyield. Collect soil samples in latewinter or early spring. Apply therecommended amount of lime 2to 3 months before planting. Besure to thoroughly mix the limewith the soil. Also apply 0.5 to 1pound of actual boron per acreprior to planting; recent researchhas shown a definite benefit inmaintaining boron levels intomatoes.

If a soil test is not done,apply enough fertilizer to supply150 to 180 pounds per acre ofnitrogen (N) and 200 to 250pounds per acre of P2O5 andK20 (potash). In any case, apply30 to 50 percent of the requiredN and K2O and 100 percent ofthe required P2O5 before trans-planting. When growing on bareground, sidedress with 25 per-cent of the remaining N and K2Ojust after the first blooms set fruitand then again 3 weeks afterthat with the last 25 percent ofthe required N and K2O. Whenusing drip irrigation, apply thepreplant fertilizers as indicatedabove. A lower percentage ofpreplant fertilizer is commonlyused (30 percent) with drip irri-gation. Sidedressing will involveweekly, biweekly, or possiblydaily injections of fertilizer mate-rials (fertigation) through thedrip irrigation system. A morecomplete explanation of fertiga-tion will follow under the“Irrigation” section of this publi-cation.

Transplants and SpacingTomatoes are an easy crop

to transplant. Grow your owntransplants to maximize yourproduction. It takes about 4 to 6weeks to produce a tomatotransplant, and 3 ounces of seedwill produce about 10,000 trans-plants. The optimal temperaturefor germination is 85 degrees F.It will take about 5 days at thattemperature for the seedlings toemerge. By growing your owntransplants, you can be certainof the cultivar, treatment of thetransplants, and overall health ofthe transplants. In addition, thetransplants will be ready whenyou need them because you dothe scheduling. You do not needto depend on a transplant opera-tion or on other growers.

If you are unable to produceyour own transplants, be surethat the transplants that you pur-chase are certified and diseasefree. It is vital to remember thatthe health of the transplant IS amajor factor in how well theplants produce later. Poor quali-ty transplants will produce poorquality fruit and lower yields.For optimal growth and estab-lishment in the field, transplantsshould not be flowering (unlessyou are using a large 3- to 4-inchcontainer for producing yourtransplants) or fruiting.

In any case, spacing general-ly depends on the variety, thetraining system, and the sprayequipment to be used. Placerows 4 to 6 feet apart with plants18 to 24 inches apart within therow. Use Table 1 to determinethe number of plants per acrerequired at various spacings.

To determine the number oftransplants required per acre forany spacings, divide 43,560(number of square feet in anacre) by the product of the de-sired spacing between plantsand the desired spacing betweenthe rows. For example, an 18-inch between-plant spacing on48-inch centers would require7,260 plants per acre: 18 inchesx 48 inches or 1.5 feet x 4 feet =6 feet2; then divide 43,560/6 =7,260 plants per acre.

VarietiesThree types of tomatoes are

produced for commercial mar-kets: traditional, large-fruitedtomatoes; cherry tomatoes; andRoma, or plum, tomatoes.Marketing channels for each ofthese types can differ a greatdeal. It is important to marketyour crop before you plant yourfirst transplant since your marketwill often determine which vari-ety (or varieties) you need togrow. Be sure to check withyour buyer so that you will havea clear understanding of what heor she is expecting.

Not all varieties are suitablefor production throughout thegrowing season. Some varietiesare specifically bred for produc-tion in the spring and early sum-mer, while others are more suit-ed to late summer and early fallproduction. Also, many varietieswere developed specifically forparticular markets, that is, eithermature-green harvest or vine-ripe harvest. Picking the correctvariety for your market is imper-ative.

Table 1. Number of Plants Per Acre Required at Various Spacings

Number of plants required per acreBetween-row spacing at various in-row spacings

18 inches 21 inches 24 inches

4 feet 7,260 6,223 5,4455 feet 5,808 4,978 4,3566 feet 4,840 4,149 3,630

Guide to Commercial Staked Tomato Production 3

New heat-set or hot-set toma-toes are entering the market.These varieties were developedto produce greater yields of highquality tomatoes under stressfulhigh temperatures common inthe summer and early fall in theSoutheast. (See the section on“Blossom Drop” for more de-tails.) Conditions such as blos-som drop and fruit roughnessprevail when day temperaturesexceed 85 degrees F and nighttemperatures exceed 72 degreesF for an extended period oftime. It appears that many ofthese varieties not only producewell under high temperatures,but also under poor growingconditions common in the spring(fluctuating low temperatures,excessive rain). Many growersare switching to these heat-tolerant tomatoes for season-long production.

Contact your county Exten-sion agent for a copy of thelatest edition of the vegetablevariety trials from the AlabamaAgricultural Experiment Stationat Auburn University. In the re-port, you will find informationon the performance of selectedtomatoes evaluated in several lo-cations throughout Alabama.Although there are a number ofcommercial varieties available,you should only grow those thatare adapted to Alabama. Trygrowing a small trial plot of sev-eral varieties each year to deter-mine which ones are best suitedto your particular market andgrowing conditions.

Staking and TyingStaking tomatoes improves

fruit quality by keeping plantsand fruits off the ground and byproviding better spray coverage.It is also easier to harvest stakedtomatoes than ground tomatoes(Figure 2). In the stakingprocess, a series of woodenstakes with twine woven aroundthe stakes is used to train the

plants to grow vertically off theground. Stakes 4- to 5-feet-longby 1-inch square are drivenabout 8 to 12 inches into the soilbetween every other plant.

Vigorous cultivars may re-quire larger and longer stakes. Astake placed between everyother plant is adequate to sup-port most determinate varieties(Figure 2). Placing an additionalstake at an angle and tied to theend stake of each section willstrengthen the trellis system(Figure 3). Stakes can be drivenby hand with a homemade dri-ving tool (usually a length of 2-inch pipe with an end cap se-cured in place) or with acommercially available, power-driven stake-driving tool. Drivestakes to a consistent depth sothat spray booms can be operat-ed in the field without damagingthe trellis system.

Select tomato twine that isresistant to weathering andstretching and that binds well tothe wooden stakes. Tomatotwine is available in 3- to 4-pound boxes. About 30 poundsper acre are required. To maketying convenient, use a home-made stringing tool. This toolcan be made from a length ofmetal conduit, a broom handle,or a wooden dowel (Figure 4).With a conduit, the string is fedthrough the pipe. With a broomhandle or wooden dowel, drilltwo small, parallel holes, eachabout 1 inch from the end tofeed the string through one holealong the length of the tool andthrough the other hole. The toolserves as an extension of theworker’s arm (the length cut tothe worker’s preference) andhelps to keep the string tight.

Proper stringing consists oftying the twine to an end stakepassing the string along one sideof the plants, looping the twinearound each stake until the endof a row or section (100-footsections with alleys may be

helpful for harvesting) is reached(Figure 4). Continue the sameprocess on the other side of therow. The string tension must betight enough to hold the plantsupright, but harvest can be diffi-cult and strings can scar fruit ifthey are too tight.

The first string should bestrung 8 to 10 inches above theground when plants are 12 to 15inches tall before they fall over.Run the next string 6 to 8 inchesabove the preceding string be-fore plants start to fall over. Mostdeterminate varieties require 3 to5 stringings. Stringing should bedone when the foliage is dry toprevent the spread of any bacte-rial diseases.

PruningPruning helps maintain a

balance between vegetative andreproductive growth. If you donot prune or prune very little,your tomato plants will produceexcessive vegetative growth withreduced fruit size.

Moderate pruning will leaveyour plants with smaller vines andlarger fruit that will mature earlier.Pruning keeps plants and fruit offthe ground, helping to control dis-eases. Although pruning requiresa lot of effort, the benefits ofdoing so are more marketablefruit, easier harvesting, and re-duced injury to plants when multi-ple harvests are being made. Thispractice is most profitable when along harvest season is possibleand when there is uniform fruitproduction over the season. Themost common method is pruninga two-stemmed plant by pinchingoff lateral branches, known assuckers, as they appear in theaxils of each leaf.

To achieve this balance, re-move all the suckers up to theone immediately below the firstflower cluster (Figure 5). A sin-gle pruning will usually be ade-quate, although a later pruningmay be needed to remove


suckers growing from theground at the base of the plant.Suckers should be removedwhen small, no more than 2 to 4inches in length. Letting themget large wastes plant energyand provides an entry point forplant pathogens.

Pruning should be done inthe early morning after plantshave dried. Indeterminate vari-eties may need to be toppedusing a knife or machete if thevines grow above the top of thestakes.

Irrigation andPolyethylene MulchBackground

Irrigation is a requirement ofany successful vegetable opera-tion. It is also critical to the pro-duction of quality tomatoes.Tomatoes as well as most veg-etables are 85 to 95 percentwater, so any loss in waterweight is equal to a loss insaleable weight. Whether usingoverhead or drip irrigation, you

need to provide enough water tothe crop to ensure optimal pro-duction. Tomatoes need 1 to 1.5inches of water per week. Thetomato is a deep-rooted crop (24inches plus) meaning that it willbe able to exploit a lot of soilarea for moisture; however, it isnot a drought-tolerant crop.Insufficient water will result inthe formation of undersized fruit,fruit with blossom-end rot, andfruit with growth cracks. All ofthis results in the production ofa significant number of culls.

In tomatoes, the most criticaltime period for irrigation is dur-ing fruit sizing. Basically, thismeans that tomatoes need a con-tinuous supply of moisture fromestablishment through the finalharvest as fruit begins to set andenlarge within 2 to 3 weeks fol-lowing transplanting. For toma-toes, the best system for supply-ing continuous moisture is dripirrigation. In most cases, you willneed to run your drip irrigationsystem daily during times ofpeak water need (heavy fruitload, low relative humidity, hightemperatures).

Figure 4. Staking and stringing operation

4 to 41⁄2’ stake

Stake-driving tool

A. Staking: Drive 4- to 41⁄2-foot stakes about 12 inches into ground midwaybetween plants. Note use of galvanized pipe for driving stakes manually.

B. First stringing: Locate about 10 inches above the ground when plants are12 to 15 inches high. Keep twine tight.

C. Second stringing: Locate about 6 inches above first when plants are 18 to20 inches high. Note stringing tool.

Stringing toolTo ball of twine at operator’s belt

First flower cluster

Remove thissucker andall below

Leave this sucker

Figure 5. Pruning of trellised toma-toes. Note position of lateral branches(suckers) and first leaf cluster.


Using polyethylene (plastic)mulch offers growers several ad-vantages. Plastic mulch increasesthe soil temperature acceleratingplant growth and development.It also conserves soil moistureand reduces several commonproblems: soil compaction andcrusting, ground rot of fruit, fer-tilizer leaching, drowning ofcrops, evaporation, and competi-tion from weeds. Black plastic(Figure 1a) is commonly usedfor spring plantings since it has-tens maturity and increasesyields while white or white-on-black plastic is best used forsummer and fall plantings whenhastening maturity is not as im-portant as the need to cool soil(Figure 1b). If white or white-on-black plastic is unavailable ortoo costly, you can spray blackplastic with a dilute solution offlat, exterior white latex paintand water (3:2 v/v). A narrow 6-to 8-inch strip down the middleof the black plastic will beenough to cool the soil and pre-vent any young transplants frombeing damaged by the high soiltemperatures typical under blackplastic in the summer.

Although using mulch willincrease production costs, thosecosts are offset by increasedprofits from earlier and largeryields of high quality produce.Drip irrigation systems must beused with plastic mulch. In addi-tion, growers can plant multiplecrops (double cropping) into theplastic mulch provided care istaken to avoid excessive damage(tears, holes, etc.) to mulch.Double cropping will spreadyour production costs over twocrops, decreasing the risk associ-ated with the higher initial set-up costs. Tomatoes can be plant-ed on mulch that was used toproduce a spring crop such ascabbage, collards, broccoli, orstrawberries. Be sure that driptape is offset 3 to 4 inches fromthe center of the bed, buried 2to 4 inches deep.

Drip IrrigationDrip irrigation can be used

on bare ground (Figure 6) or incombination with any organic orsynthetic mulching material(Figure 7). Drip irrigation ofstaked tomatoes using raisedbeds covered with plastic mulchhas resulted in higher yields andbetter quality fruit. While toma-toes grown using conventionalsprinkler irrigation may yield ap-proximately 800 25-pound boxesper acre, drip irrigated tomatoeswith plastic mulch may yieldfrom 1,500 to 2,000 boxes peracre. Because water and fertilizercan be precisely controlled,tomato quality is often superior.Thus, the market value for suchtomatoes is higher depending onthe market in any given year.

Management RequirementsDrip irrigation of staked

tomatoes requires added atten-tion to detail and increased man-agement supervision in order toproduce the high-quality, pre-dictable crop required for ship-ment to markets throughout thecountry. The plastic mulch tech-nique does increase labor andpreharvest costs; however, thiscost increase is more than offsetby the increase in both fruitquality and quantity.

The drip system may need tobe chlorinated regularly andshould be closely monitored forproper operation. To avoid pos-sible leaching or salinity prob-lems, fertilizer applicationsthrough the system should bemade on a frequent, often dailybasis. Since rainfall will not re-plenish soil moisture under theplastic mulch, the moisture lev-els must be carefully monitoredand irrigation events scheduledto meet the plants’ water re-quirements.

Bed PreparationStaked tomatoes are produced

on raised beds that are typically 4to 6 inches high and 30 to 36inches wide. Special equipment isused to form the beds and lay theplastic mulch. Careful attention tothe soil condition and to the ad-justment of equipment is neededto form beds and to place theplastic so that it will stay in placeand provide an optimum environ-ment for the tomato root system.Beds are shaped, pressed, fertil-ized, and fumigated (if necessary)in one operation. After the bedsare shaped, the plastic mulch anddrip tubing are then laid in a sin-gle operation.

Equipment required includesa bed press, equipment for fumi-gating the soil, and equipmentfor laying the plastic mulch anddrip tubing. An alternative soilfumigation method is to injectthe fumigant through the irriga-tion system after the plasticmulch is laid. With eithermethod caution should be exer-cised before planting to ensurethat the fumigant has dissipatedand the beds are suitable forplanting. Be sure to read thelabel for the fumigant sincesome may require up to 2 weeksto completely dissipate.

Drip Lateral OptionsTwo types of drip irrigation

laterals, drip tape (Figure 8) andin-line tubing, are commonlyused for irrigating staked toma-toes on plastic mulch coveredbeds. Drip tape has emittersformed in the tape as part of themanufacturing process and is arelatively inexpensive, throw-away product used for only onegrowing season. In-line tubinghas drip emitters factory-installedinside the tube and usually ismade of heavier gauge materialso that it can be used for a num-ber of growing seasons. Whenused for more than one growing


season, in-line tubing has to berecovered and rolled onto alarge spool for storage.

In-line and tape products aremanufactured with outletsspaced at uniform intervals,ranging from 4 to 24 inches ormore. The spacing selectedshould be based on the soil typeand crop. For tomatoes, 8-inchspacing is commonly used onsandy soils; 12-inch spacing iscommonly used on heavier soiltypes.

The tape or in-line tube isplaced to one side of the centerof the row, normally 3 to 4 inch-es from the center and 2 to 4inches deep in the bed. Stakesand tomato plants can then beplaced down the center of therow without damaging the dripirrigation laterals.

Whether using drip tape orin-line tubing, care must betaken to ensure that the outletsdo not become plugged duringthe growing season. Proper fil-tration and a routine chlorinationand flushing maintenance pro-gram can accomplish this. Forinformation on chlorination,contact your county Extensionagent.

System DesignThe irrigation system should

be able to apply an amount ofwater equal to 75 percent of themaximum expected daily panevaporation (PE), based on thetotal field area (excluding harvest

roads). This application amount isthe minimum design requirementand should take care of the maxi-mum water needs of the crop. Ata PE of .35, the highest normallyexpected in Alabama, the designpeak application amount is .26inches or 7,128 gallons per acreper day. Note that this is the actu-al water application amountneeded. Since the expected appli-cation efficiency of drip system is80 to 90 percent, the designpumping capacity should be7,920 to 8,910 gallons per acreper day.

Because this water is appliedonly along rows, bed spacingwill affect the amounts to be ap-plied per row foot. For example,assuming 80 percent efficiency,the design pumping capabilityshould be 123 gallons per dayper 100 feet of bed for bedsspaced 6 feet apart (3-foot bedwidth) and 102 gallons per dayper 100 feet with 5-foot spacing(2-foot bed width).

This design rate would onlybe applied in the most extremecases, such as drought with ma-ture plants, high temperatureand wind, low humidity, and noclouds. The actual quantity ap-plied each day will depend onthe water used by the crop. Forexample, less water would beapplied early in the growing sea-son, when the plants are small,or on days with moderateweather conditions.

The operating time neededto apply a given amount of

water will depend on the flowrate of the drip tape or in-linetubing used. For example, if driptape with a flow rate of 0.45gpm per 100 feet is used, it willtake 4 hours 37 minutes to deliv-er 123 gallons per 100 bed-feet.Find the total daily operatingtime by dividing the amountneeded (gallons) per 100 feet bythe tape flow rate (gallons perminute) per 100 feet.

FertigationFertilization of plastic-

mulched tomatoes should bebased on soil test recommenda-tions. Around 30 to 50 percentof the nitrogen and potassiumneeded by the crop is usually in-corporated into the bed beforeplanting and the rest appliedthrough the irrigation systemthroughout the growing season.Phosphorus is not recommendedfor injection in irrigation sys-tems, and 100 percent of thephosphorus requirement shouldbe applied preplant. Commercialliquid fertilizer materials aremuch easier to apply throughthe system than are dry fertiliz-ers, and they are less likely tocause clogging.

Adjustments of the amountsof N and K to be applied pre-plant or injected are made in ac-cordance with the soil test rec-ommendation and the analysisof the fertilizer material used.The key is that the proportionsof N and K injected shouldmatch the fertilizer analysis.

Table 2. Example of Preplant vs Injected Fertilizer Amounts

A B C D E

Fertilizer Total Preplant N Injected N (B - C) and K Preplant Kanalysis fertilization (30-40%) (N:K ratio to match (B - D)

(N:K ratio) recommendation analysis, Col. A)

7-0-7 180 lb N60 lb N (33%)

120 lb N1:1 ratio

(1:1 ratio) 180 lb K 120 lb K 60 lb K

7-0-7 180 lb N60 lb N (33%)

120 lb N1:1 ratio

(1:1 ratio) 240 lb K 120 lb K 120 lb K

5-0-10 180 lb N72 lb N (40%)

108 lb N1:2 ratio

(1:2 ratio) 240 lb K 216 lb K 24 lb K


Usually, nitrogen is taken as thefirst element to allocate to pre-plant or injection application. InTable 2 you will see examples oftypical choices made for differ-ent fertilization recommenda-tions and fertilizer materialanalyses.

Table 3 shows the recom-mended percentages to be in-jected during each week in atypical 12-week tomato-growingseason. The idea is to match fer-tilization amounts with theplant’s requirements at each

growth stage. Note that the per-centages refer only to the por-tion of the recommendation tobe injected, not to the entire fer-tilizer requirement. The actualamounts injected (pounds or gal-lons) will depend on the soil testrecommendation and the fertiliz-er analysis. The breakdown isgiven on a weekly basis; howev-er, daily injection (or 6 days aweek) is preferable to minimizepossible leaching and undesir-able salinity problems. It is al-ways better to inject smaller

amounts of fertilizers more fre-quently on sandy soils (such asdaily or every other day). Withsoils that contain more clay, lessfrequent injections such as onceor twice per week are common.

An example of a tomato fer-tigation schedule below showshow amounts to be injected canbe calculated to make up a de-tailed fertigation schedule (Table4). Note that this is an exampleonly. Columns A and B (basicfertigation schedule) would begenerally applicable for toma-toes having a 12-week growingseason. However, a completefertigation schedule for a partic-ular variety in a given field canonly be developed with all of

Table 3. Percentage of Injected Fertilizer to Apply Per Week (For 12-WeekTomato Crop)

Week 1 2 3 4 5 6 7 8 9 10 11 12

% to 1% 3% 4% 6% 8% 9% 11% 15% 11% 11% 11% 10%inject

Table 4. Example of a Tomato Fertigation Schedule

Soil test fertilization 180 lb N/acre Irrigation zone size: 10 acresrecommendation: 240 lb K/acre

Fertigation schedule: 6 days/wk

Preplant application amounts: 60 lb N/acre Fertilizer material: 7-0-7 (liquid)120 lb K/acre

Amounts to be injected: 120 lb N/acre Liquid fertilizer weight: 10.5 lb/gal120 lb K/acre

Basic Actual fertilizer amounts needed Gallons of 7-0-7fertigation for injection to be injected

schedule fortomatoes

A B C D E F G H I J K

Week % fert. lb N/ lb N/ lb N/ lb K/ lb K/ lb K/ gal/ gal/ gal/Inject/ wk/ day/ day/ wk/ day/ day/ wk/ day/ day/

wk acre acre zone acre acre zone acre acre zone

1 1% 1.2 0.2 2.0 1.2 0.2 2.0 1.63 0.27 2.7

2 3% 3.6 0.6 6.0 3.6 0.6 6.0 4.90 0.82 8.2

3 4% 4.8 0.8 8.0 4.8 0.8 8.0 6.53 1.09 10.9

4 6% 7.2 1.2 12.0 7.2 1.2 12.0 9.80 1.63 16.3

5 8% 9.6 1.6 16.0 9.6 1.6 16.0 13.06 2.18 21.8

6 9% 10.8 1.8 18.0 10.8 1.8 18.0 14.69 2.45 24.5

7 11% 13.2 2.2 22.0 13.2 2.2 22.0 17.69 2.99 29.9

8 15% 18.0 3.0 30.0 18.0 3.0 30.0 24.49 4.08 40.8

9 11% 13.2 2.2 22.0 13.2 2.2 22.06 17.9 2.99 29.9

10 11% 13.2 2.2 22.0 13.2 2.2 22.0 17.96 2.99 29.9

11 11% 13.2 2.2 22.0 13.2 2.2 22.06 17.9 2.99 29.9

12 10% 12.0 2.0 20.0 12.0 2.0 20.0 16.33 2.72 27.2Explanations: Column C = B/100 x 120 lb Column F = B/100 x 120 lb. Column I = C lb ÷ 0.735 lb/galColumn D = C lb ÷ 6 days/wk Column G = F lb ÷ 6 days/wk Column J = I gal ÷ 6 days/wkColumn E = D lb. x 10 acres Column H = G lb. x 10 acres Column K = J gal x 10 acres


the information from the soiltest, the zone size, the fertilizermaterial analysis, etc.

If liquid fertilizer materialsare used, the weight (pound/gal-lon) of the fertilizer materialused must be known. In thesample fertigation schedule, forexample, week 4 calls for 6 per-cent of the 120 pounds of actualN (per acre) to be injected, or7.2 pounds. This figure must beconverted to gallons of liquidfertilizer. Using a 7-0-7 fertilizermaterial that weighs 10.5 poundsper gallon, each gallon contains0.735 pounds actual N (0.07 x10.5 lb= 0.735 lb). To get 7.2pounds actual N then requires9.8 gallons (7.2 lb ÷ 0.735 lb/gal= 9.8 gal), as shown in ColumnI. For further details on fertiga-tion, contact your countyExtension agent.

SchedulingScheduling is the process by

which decisions of when to irri-gate and how much water toapply are made. For tomatoesgrown on plastic mulch withdrip irrigation, a scheduling planthat maintains nearly optimal soilmoisture conditions is recom-mended. This means that the ir-rigation system is usually operat-ed daily. On very sandy soils thesystem may even have to oper-ate more than once per day tomaintain the desired level of soilmoisture.

Tensiometers are recom-mended for monitoring soilmoisture, placed at both 6-inchand 12-inch depths in the bedand located 4 to 6 inches offsetfrom the drip tape and midwaybetween plants (Figure 9).Tensiometers at 12 inches moni-tor root development and mois-ture extraction at and below 12inches. Tensiometers with tipsplaced at 6 inches are the pri-mary indicators for scheduling ir-rigation. Irrigation should bescheduled so tensiometer

readings will be maintained inthe 10 to 15 centibar range, al-lowing not more than 20 percentdepletion of soil moisture. Closemonitoring of soil moisture isneeded, especially on sandysoils or where plant root systemsare restricted, such as growingtomatoes on plastic mulch.

Physiological Disorders(Problems Not Causedby Diseases or Insects)Blossom-End Rot

Blossom-end rot (BER) is aphysiological disorder, not a dis-ease. It is easily identified as abrown, leathery rot developingon or near the blossom end ofthe fruit (Figure 10a). It startswith a dry, brown lesion the sizeof a dime and generally increas-es in diameter as the conditionworsens. In time, lesions oftenbecome covered with a blackmold.

BER is caused by calcium de-ficiency, usually due to fluctua-tions in water supply. Becausecalcium is not a highly mobileelement in the plant, even briefchanges in the water supply cancause BER. Droughty soil or dam-age to the roots from excessive orimproper cultivation, i.e., rootpruning, that restricts water intakecan prevent plants from gettingthe calcium they need from thesoil. Also, if plants are growingunder high relative humidity inhighly acidic soil or are gettingtoo much water from either heavyrain or overirrigation, they can de-velop calcium deficiency andBER. With any of these cases,high temperatures (above 90 de-grees F) will make BER worse.

To control BER, take the following steps:

1. Keep the soil’s pH at 6.0 to6.8. Perform a soil test andapply the recommended rate oflime, using dolomitic or high-calcium limestone. Be sure to

apply lime and fully incorporatelime 2 to 4 months before plant-ing tomatoes.

2. Apply the required amountof fertilizer when necessary asbased on soil test results fortomato. Applying too much fer-tilizer at one time can induceBER. Following soil test recom-mendations is the surest way tofertilize properly.

3. Use mulches to conservemoisture. Use pine straw, straw,decomposed sawdust, plastic, ornewspapers. Mulches conservesoil moisture and reduce the in-cidence of BER.

4. Give your plants adequatewater. Tomato plants need about1.5 inches of water per weekduring fruiting. Extreme fluctua-tions in soil moisture can resultin a greater incidence of BER.

5. If your plants develop BER,spray them with a calcium solu-tion at the rate of 4 pounds ofcalcium nitrate or calcium chlo-ride per 100 gallons of water (or4 level tablespoons per gallon ofwater). Be careful with calciumchloride. If day temperatures arehigher than 85 to 90 degrees F,calcium chloride can burnplants. Under high temperatures,use calcium nitrate. You shouldspray two or three times eachweek, beginning when the sec-ond fruit clusters are blooming.Spraying calcium is not asubstitute for proper irrigationand fertility management.

6. Try growing several vari-eties and keep notes of their per-formance under your growingconditions. Some tomato vari-eties tend to be more sensitiveto conditions that cause BER.

7. Remove fruits with BER.Once a fruit develops BER, itwill not regrow or repair the in-fected area. Remove the fruit;otherwise, these damaged areas


could serve as entry points fordisease-causing bacteria, fungi,and insects.

Blossom DropThis condition is NOT relat-

ed to any nutritional disorder,disease, or insect damage. It isrelated to temperature. Despitethe fact that tomatoes evolved inthe tropics, flowering in toma-toes is sensitive to temperature.When day temperatures exceed85 degrees F and night tempera-tures exceed 72 degrees F, toma-to flowers often abort. An impor-tant temperature factor is time ofexposure. The longer the plantsare exposed to those high tem-peratures, the longer the condi-tion will last and the more seri-ous the effect will be onflowering. Short exposures ofonly 2 to 3 days may not causemuch of a problem. It is interest-ing to note that although thecombination of high day andnight temperatures causes blos-som drop, high night tempera-tures alone can be detrimental toflowering even if day tempera-tures are not over 85 degrees F.

Heirloom and older homegarden varieties are more sensi-tive to high temperatures thanare many of the newer hybridsthat are presently available.When the fruit does not set andall other conditions are other-wise favorable (sufficient waterand fertilizer, good pest control,appropriate pH), plants generallybecome vigorous and darkgreen. Even new hybrids, how-ever, can be susceptible to blos-som drop especially underprolonged adverse conditions.

Commercial growers in theSoutheastern United States havesuffered with this problem formany years until the recent ad-vent of “heat set” tomato vari-eties. These varieties have beenbred for tolerance to high dayand night temperatures commonin the summer and early fall. In

fact, many of these varieties setfruit under poor growing condi-tions—extended cool, rainy peri-ods as well as during extendedperiods of hot weather.

If this condition has devel-oped in your planting, keep theplants healthy and watered.Maintain fertility levels and con-trol any pest problems since anyadditional stress will make thecondition worse. The plants willproduce flowers and set fruitwhen temperatures becomemore favorable.

For your next crop, try grow-ing a “heat set” variety. Manyseed catalogs carry a wide rangeof tomatoes. Read the descrip-tions carefully looking for phras-es such as “heat set,” “hot set,”or “heat tolerant.” Often thosevarieties have references to theirheat tolerance in their names.Varieties such as ‘Sunbeam,’‘Sunmaster,’ ‘Suncrest,’ and ‘SunLeaper’ have performed well inAlabama even during extendedperiods of hot weather and havebecome a mainstay for many ofour commercial tomato growers.

PuffinessThis problem is worse under

conditions of high nitrogen andlow light (short days or cloudyweather) and when the nitrogen-to-potassium ratio is not in bal-ance. It occurs more frequentlyafter rainfall, particularly whenaccompanied by low tempera-tures. Anything that interfereswith pollination (low light, ex-cessive nitrogen, temperaturesbelow 58 degrees F, or tempera-tures above 95 degrees F duringthe day and above 70 degrees Fat night) leads to a greater inci-dence of puffiness.

Catfacing and RoughBlossom Scars

These problems are more se-rious with large-fruited varietiesthan they are with cherry or

Roma tomatoes (Figure 10b).They are more prevalent if theweather is cool and cloudy atthe time of bloom. Some publi-cations list “open locule” as aform of catfacing. Open loculehas been found more frequentlywhen boron is deficient.

Fruit CracksThere are two distinct types

of fruit cracking: radial and con-centric. Radial cracking is themost common and results in themost fruit damage (Figure 11). Itoccurs more often during rainyperiods when the temperature isrelatively high, especially whenrains follow a long, dry period.Radial cracking is more severeon ripening fruits, especially ifthey are exposed to the sun.Concentric cracking begins ongreen fruits that are fully ex-posed to the sun (Figure 11).Maintaining a uniform watersupply throughout the growingseason with drip irrigation,mulches, or both, and maintain-ing good foliage cover will helpreduce fruit cracks.

SunscaldSunscald can be a problem

on both large-fruited and Romatomatoes. The condition is com-monly a problem with green-shouldered varieties or varietiesthat do not produce sufficient fo-liage to cover developing fruit.Producing poor foliage covercan be a function of the variety(low vigor variety) or it can beinduced by insufficient nitrogenlevels. The condition is charac-terized by the development ofvery dark green shoulders whenthe fruit is still immature. As thefruit develops, the shouldersbegin to turn yellow (Figure 11)and remain so making the fruitunmarketable. Also, sudden ex-posure of the fruit to sunlightcan cause sunscald. Avoid anyunnecessary damage to theplant’s canopy during harvest


that would result in exposing de-veloping fruit to sunlight.

Gray WallAlso called blotchy ripening,

gray wall is more severe whenthe nitrogen level is excessive,the soil is poorly drained, the ni-trogen-to-potassium ratio is notin balance, and the soil pH islow. Selecting well-drained soilsand fertilizing according to thesoil test recommendations willreduce this problem.

Harvesting TomatoesThere is no money in grow-

ing tomatoes—just in sellingthem. Therefore, it is essentialthat you harvest your tomatoesat the stage of maturity that yourmarket desires. Every growershould plan ahead and spendthe necessary time training yourworkers to recognize the differ-ent stages of maturity of thetomato.

Mature GreenFor shipping to distant mar-kets, fruits generally are har-vested at the mature greenstage, which is when thefruit will ripen normallywhen removed from theplant (Figure 12). The bestway to determine if the fruithas reached the maturegreen stage is to collect asample of fruits and cut eachcrosswise. If the knife passesthrough the fruit withoutcutting any seeds, then thefruit is mature green.Otherwise, the fruit is imma-ture green and will not colorup and ripen properly whenpicked. For some varieties, alight or whitish color devel-ops at the blossom end ofthe fruit at the mature greenstage. For the first harvest,growers will wait until about10 percent of the fruit on thefirst flower cluster is at thebreaker stage of maturity,which is when a flush of

pink color develops on theblossom end of the fruit. Allfruit on the first two flowerclusters is removed. At thesecond harvest, which isusually 10 to 14 days afterthe first, mature fruit fromthe middle of the plant is re-moved. Maturity for the sec-ond harvest is based primari-ly on size; only fruit that is 2inches in diameter and largeris removed. At the third har-vest, 10 to 14 days after thesecond, fruit is removedfrom the upper portion ofthe plant.

Vine RipeFruit for vine ripe productionshould be harvested at thebreaker stage of maturity(the point at which a flush ofpink color develops on theblossom end of the fruit). Atthis stage, fruit can be har-vested, handled, andshipped with less damagethan fruit with more color. Itwill also bring a higher price.Plan on harvesting everyother day during the peak ofthe season. Vine ripe fruittend to bring a higher pricein the fresh market com-pared to mature green fruit. Pinks/Light Reds (60 to 90Percent Red)For local markets, allowfruits to develop morecolor—pink to red stage. Forthe pink market, harvestingshould be done daily or atleast every other day accord-

ing to the pinkness desired.Since these fruits are moremature than mature green orbreakers are, their shelf lifewill be reduced and they willbe easier to bruise.

For any local or distant mar-ket, always pack in the size con-tainer your market wants. Thisusually is a 20-, 25-, or 30-pound cardboard carton. Pack toassure uniform size, color, andquality. With proper culturalpractices, tomatoes can produce1,500 to 2,000 25-pound boxesof fruit per acre when usingplastic mulch and drip irrigation.On bare ground with irrigation,expect yields to be around 80025-pound boxes per acre.

Cooling and Storage of Tomatoes

The following recommenda-tions are adapted from TheCommercial Storage of Fruits,Vegetables, and Florist andNursery Stock, 1986, USDA,Agricultural Handbook No. 66.Be sure that all harvest bins areclean of any debris or soil.Placing padding in bulk bins canreduce damage to fruit. Whenemptying bins or containers,never drop fruit from any higherthan necessary (Figure 13).

Remove tomatoes from thefield immediately after harvestsince tomatoes (fruit) can losewater rapidly and their qualitywill suffer when they are notcooled promptly. Forced-air androom cooling are both suitable

Table 5. Storage Temperatures and Shelf Life

Stage of Maturity Storage Temperatures Length of Storage

Mature green 55 to 70 degrees F w/ 85 to 95 1 to 3 weekspercent relative humidity

Pink 50 to 60 degrees F w/ 85 to 95 5 to 10 days percent relative humidity

Ripe 45 to 50 degrees F w/ 85 to 95 4 to 7 dayspercent relative humidity

J.M. Kemble, Extension Horticulturist, Associate Professor, Horticulture; T.W. Tyson, Extension Agricultural Engineer, Professor, AgriculturalEngineering; and L.M. Curtis, former Extension Agricultural Engineer, all withAuburn University

For more information, call your county Extension office. Look in your tele-phone directory under your county’s name to find the number.Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The AlabamaCooperative Extension System (Alabama A&M University and Auburn University) offers educational programs,materials, and equal opportunity employment to all people without regard to race, color, national origin, religion,sex, age, veteran status, or disability. 4M, Revised May 2004, ANR-1156

© 2004 by the Alabama Cooperative Extension System. All rights reserved.

ANR-1156

for tomatoes. Never use ice orchilled water to cool fruit. If youare using a tank to wash fruit,the temperature of the water inthe tank should be close to theinternal temperature of the fruit,the pulp temperature. Placinghot fruit in cold water will signif-icantly reduce the post-harvestlife of the fruit.

Ripening of tomatoes is initi-ated by ethylene that they pro-duce. It can also be induced byexposing mature green fruit toethylene using a device that pro-duces it. Mature green fruit iscommonly treated with ethyleneto hasten ripening and providemore uniform ripening within aparticular lot. For treatment,tomatoes are exposed to 100 to150 ppm ethylene for 24 to 48hours at 68 to 78 degrees F with85 to 90 percent relative humidi-ty. Treating fruit that is beyondthe breaker stage of maturitywith ethylene will not provideany benefit since these fruits arealready producing their own eth-ylene.

Precise temperature controlis critical to maintaining accept-able quality in tomatoes. UseTable 5 to determine the optimalstorage temperature for the par-ticular fruit stage that you areconcerned with. Note that as

fruit becomes more mature, itsoptimal storage temperature de-creases and its shelf life decreas-es. Tomatoes are very sensitiveto chilling. Never store tomatoesbelow the low temperatures rec-ommended in Table 5.

References• Curtis, L.M., S. Kovach, and T.Tyson. 1992. Micro-irrigationand energy conservation: com-mercial tomatoes. The AlabamaCooperative Extension System,ANR-660.

• Konsler, T.R. and R.G.Gardner. 1990. Commercial pro-duction of staked tomatoes inNorth Carolina, AG-405. NorthCarolina Agricultural ExtensionService.

Figure 13. A major problem—drop-ping fruit from an excessive height.You might not see the damage imme-diately, but this causes a great deal ofbruising. The consumer will see thedamage.

Figure 7. Contrast between plasticmulch and an organic mulch (woodchips)—same variety, same plantingday, same fertilizer/watering schedule.The tomatoes on black plastic are al-most 2 weeks ahead of those underthe wood chips.

Figure 6. Use of drip irrigation fortrellised tomato production on bareground

Figure 12. Close-up of mature greenfruit ready for harvest

Figure 11. Radial (note corky areason top of fruit) and concentric crack-ing (circling around the shoulders ofthe fruit). Also note yellowing ofshoulders due to sunscald.

Figure 10b. Rough blossom scars/catfacing on fruit

Figure 10a. Blossom-end rot ontomato

Figure 9. Tensiometers used to moni-tor soil moisture levels. Used in pairsto determine when to start irrigatingand how effective your irrigationscheduling is. On right, close-up ofgauge.

Figure 8. Close-up of drip tape andwetting pattern produced by surfaceplaced tape. Drip tape can either beburied or placed on the surface.

Figure 2. Close-up of trellising system

Figure 3. Double stakes used on endrows to lend strength to the trellisingsystem

alabama a&m and auburn universities guide to commercial staked tomato production in ... ·...

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