DP Tool Club 17/CD_ASCQ_17_101194.iso/vrac/grnhse.zip/GRNHSE.003

Text File | 1994-08-30 | 19KB | 435 lines

        GREENHOUSE TOMATO PRODUCTION -- THE SOIL SYSTEM
                     Jonathan R. Schultheis
              Extension Horticultural Specialist
            September 1993   LEAFLET NO. 32  (Reprinted)


GENERAL. Production of tomatoes out of season in plastic
greenhouses can be profitable. It requires considerable and
exacting knowledge and care. It is concentrated production in a
small space under ideal conditions.  One mistake can reduce
profits considerably.  Production should be attempted only if
sufficient time is allotted and money is available to do a
complete job throughout the entire growing season. Generally,
growing a fall crop is less profitable due to low light
intensity, poor fruit set, poor fruit quality, and high fuel
costs.

Plastic houses are popular because of their low cost.  Many
commercial greenhouse packages are available that can be
commercially built or installed by the grower.  Two crops of
tomatoes per year are possible -- late spring and late fall.
Fall crops produce about one-half as well as spring crops.


COSTS AND RETURNS.  Plastic houses will cost about $3.00-$8.00
per square foot depending on design, materials and labor.  Four
thousand (4,000) square feet is considered a minimum economic
unit.  This will produce enough greenhouse tomatoes to supply the
market for about 10,000 people.  A total of 4-5 pounds (combined
spring and fall) of fruit can be produced per square foot.  Price
to grower has averaged about $1.00-$1.25 per pound wholesale and
$1.50-$1.75 retail for number one grade.


OPERATING SCHEDULE.  The following schedule of operation is
typical for greenhouse tomato production in North Carolina.

                        Spring Crop         Fall Crop
Plant seeds in
plant bed (or flats)    Nov. 20-Dec. 5      June 10-20

Transplant seedlings                        June 20-
to pot                  Dec. 1-5            July 5

Set plants in
plastic house           Jan. 15-31          Aug. 1-15

Spray plants for        Every 7-10          Every 7-10
diseases (insects         days                days
if present)

Start vibrating plants
for pollination         March 1-15          Sept. 1-15

Sidedress with nitrogen
and potash              4-6 times           4-6 times

Start harvesting
tomatoes                April 15-30         Oct. 15-30

End harvesting and
clean up house          July 1-15           Dec. 15-31

Yield per plant         10-16 lbs           6-8 lbs

Yield per square foot   2-3 lbs             1-2 lbs



GREENHOUSE.  Build houses on a well drained site, in full
sunlight, available to water and convenient to attendant.  Most
frames are of metal pipe.  When wooden frames are used, they
should be treated with a non-toxic preservative (such as copper
naphthenate) and then painted white. Clear polyethylene is one of
the less costly materials for covering. The newer materials will
normally last through two spring crops.  Use two layers of film
with a dead air space in between.  This will reduce heat cost by
about one-third and reduce excessive moisture from condensation.
Use 6 mil polyethylene for outside layer and 4 mil for inner
layer.  A small blower may be used to keep the two layers
separated for better insulation.

Ridge and furrow (gutter-connected) construction will require
less heat than a comparable area covered by separate greenhouses.



SOILS.  Select a soil that is rich, loamy, well drained, high in
organic matter, and preferably with a clay base.  Tile drain.
Stable manure, peat, sawdust, etc., may be used to build up
organic matter.  Test soil for lime and fertilizer requirements
before each crop.  Soil sample boxes and sheets should indicate
"Greenhouse Tomatoes" as crop to be grown.  Soil pH should be 6.5
to 6.8 with phosphorous and potash at the Very High level.  Plow
10-12 inches deep.  Fumigate before each crop to reduce disease
and weed problems.  Consult your county extension agent or the
current N. C. Agricultural Chemicals Manual for materials to use,
rates needed, and required waiting period.  Solarization can also
be used to reduce disease and insects by closing the greenhouse
for at least 2 weeks during the hot summer months if the
greenhouse is not being utilized.


HEATING.  Gas heaters, wood furnaces or wood fired hot water
heaters are probably most practical for greenhouse vegetable
operations.  Smoke and fumes from heating are toxic to plants;
therefore, flues must be tight.  The heat should be
thermostatically controlled.  Size of heating unit required may
be calculated by using this formula:
    (Square feet of exposed surface) x (1.2 for single layer
    of plastic) or (.8 for double layer of plastic) x
    (minimum required inside temperature minus minimum
    expected outside temperature) = BTU's required.

Example:  Your house has 4,000 square feet of exposed surface,
you have a single layer of polyethylene, your minimum required
house temperature is 58 F and you expect the outside temperature
to get as low as 10 F. The calculation would be 4,000 x 1.2 x 48
(58 minus 10) = 230,400 BTU's required.

If the wind velocity averages over 15 miles per hour during the
heating season, the heat requirement should be increased by 4%
for each 5 mph above 15 mph.

Since heat rises, a circulating or turbulating fan, operating
continuously, will stir the air, which will help maintain a more
uniform temperature throughout the house, and will reduce
condensation and reduce your heat bill.  A polyethylene tube near
the top of the house is most often used for this purpose.


VENTILATION. Ventilation is necessary to control temperature,
control humidity, and replenish carbon dioxide needed by the
plants.  Without ventilation, temperatures can build up to above
100 F when outside temperatures are much lower.  Temperatures
above 90 F are detrimental to fruit set and plant growth.  Most
growers use thermostatically controlled fans with enough capacity
to change the air in the house in one minute.  High humidity
results in condensation, greater disease problems, and less
light.  Even on cold days and at night ventilation is necessary
to exhaust "wet air" and bring in "dry air" and carbon dioxide.
Ventilators should be located high enough so that the cold air
comes in above the growing plants.  Many growers are using poly-
ethylene tubes for ventilation.  These tubes extend the entire
length of the house, are about 3 feet in diameter, held up by
wire and have 3 inch holes every 3-5 feet on both sides of the
tube.  One end of the tube may be connected around the
ventilating fan; the other end to louvered shutters.  This allows
fresh air to be brought in gradually without chilling the plants
and exhausts the warmest air which is near the top of the house.
The temperature to maintain in your house will depend on the
outside weather -- primarily sunlight. The following temperatures
are considered ideal:

    Sunny Weather       Cloudy Weather

    Day--70 -80 F       Day--65 F-75 F

    Night--58 F-60 F    Night--57 F-58


Night temperatures below those indicated could result in poor
fruit set.  Higher temperatures often result in rapid vegetative
growth, spindly plants, poor fruit set, and lower yields.


VARIETIES. Size, color, freedom from cracking and blemishes,
shape, yield, and flavor are important.  Most field varieties do
not grow well in greenhouses.  The following varieties have
performed well in North Carolina.

Laura - large beefsteak type semi-greenback; round, slightly
ribbed and very firm fruit.  Strong growth and short internodes.


Perfecto - large beefsteak type, round slightly ribbed and very
firm fruit; short jointed open plant habit.  Leave 4-5 fruit per
truss for optimum grading.

Caruso - large beefsteak variety, semi-greenback type. Nice round
fruit shape, slightly ribbed.  Medium to strong growth, open
plant habit.

Concreto - large beefsteak variety, round and slightly ribbed,
very firm fruit of excellent quality; very resistant to fruit
cracking. Short and sturdy truss stem and lower number of flowers
per truss.

Jumbo - large beefsteak type, short jointed plant habit,
resistance to verticillium with Fusarium race 2, and cladasporium
races A & B.

Dombello - beefsteak variety, compact plant habit.  The fruit is
of the greenback type with a particularly deep color at maturity.


TRANSPLANTS.  Grow your own plants. Start seed in flats and
transplant to 3 inch peat or plastic pots in 10-14 days (when
first true leaf appears).  One ounce of seed has about 10,000
seeds and will produce about 6,000 plants.  It is recommended
that a soilless or artificial growing media be used in transplant
production.  The advantage of a soilless or artificial media over
natural potting soil is its sterile nature, thus eliminating the
need to sterilize or fumigate the material.  Most mixes will have
a "nutrient charge" added but supplemental fertilizing will be
needed.


FERTILIZATION.  Test soil before each crop.  Uniformly broadcast
the amount of fertilizer and lime recommended by the soil test
report and mix it well into the upper 8-10 inches of soil before
planting.  Be sure to apply the recommended amount of Boron --
usually one-third (1/3) pound of Borax (11.3% B) per 1000 square
feet.

Soluble salts tend to build up in greenhouse soil from the
fertilizers added.  To reduce soluble salts build up, use
fertilizers that do not build up salt, such as:

Calcium nitrate = 15.5-0-0
Potassium nitrate = 13-0-44
Treble superphosphate = 0-46-0
Diammonium phosphate = 18-48-0
Potassium sulfate = 0-0-48
Sulphate of potash-magnesia = 0-0-22, 11 mg.


SETTING PLANTS.  Plant in rows about 3 feet apart with plants
16-18 inches apart in row.  Each plant should have 3.5-4 square
feet of growing space.  Run rows lengthwise in the house.  Plow
out a slight furrow (about 8 inches wide and 4 inches deep) down
the row.  Set plants in the furrow so that the top of the peat
pot is at least an inch below the soil line.  The furrows will
make watering easier and will eliminate walking on wet soil in
between the rows.  Water newly-set plants with a starter solution
using a fertilizer that is high in phosphorous and medium to low
in potash and nitrogen.


SIDE DRESSING.  Sidedress the plants 3-4 weeks after
transplanting and at 2-3 week intervals thereafter with
sufficient material to supply 1.5 pounds of N and 2.0 pounds of
K2O per 1000 square feet with each application.  Continue
sidedressing until last cluster of fruit is set.  Study your soil
test report.  Sidedress the plants and water the fertilizer into
the soil.  Do not allow the fertilizer to contact the foliage.
Either one of the following combinations of materials will
provide the proper amount per sidedressing per 1000 square feet:

   (1)  6.5 pounds of calcium nitrate plus 4.4 pounds of
        potassium nitrate

                               or

   (2)  9.5 pounds of calcium nitrate plus 4 pounds of sulfate of
        potash.

Some growers prefer to sidedress weekly at reduced rates.  Others
apply the fertilizer in the watering system weekly.  Still others
use the following sidedressing practice:

First 5 weeks -- 2 pounds of 20-20-20 per 1000 square feet per
    week.
Second 5 weeks -- 2 pounds of 20-20-20 plus 1 pound of potassium
    nitrate per 1000 square feet per week.
Remainder of the season -- 2 pounds of 20-20-20 plus 2 pounds of
    potassium nitrate per 1000 square feet per week.

The above suggestions are for a Spring crop.  Sidedress for the
Fall crop is usually about one-half of that for the Spring crop.

The rate and frequency of sidedressing should vary depending on
amount of sunlight, color of foliage, size of stems, fruit load,
and tissue analysis report.

The N. C. Department of Agriculture has a Plant Analysis
Laboratory.  It should be used to check the nutrients that are in
the tomato leaves to determine if your fertilizer program is
adequate.  Your County Extension Office has plant analysis kits
for taking these leaf samples.  There is a fee for this service.


It is suggested that a grower take a leaf sample about 4 weeks
after setting the plants in the greenhouse to determine if the
plants have an adequate supply of plant nutrients.  Be sure to
fill out the information sheet properly and take the leaf samples
exactly as recommended on the instruction sheet.  Results of the
test should be returned to you in about 5-10 days, giving you the
analysis and recommendations for further fertilization.

TRAINING.  Train plants to one stem -- remove suckers twice a
week when they first become noticeable and before they become 4
inches long.  Plants are trained up a trellis.  The trellis
consists of putting up a 10-12 gauge wire 6-7 feet above the row
and running a piece of plastic twine above each plant from the
top wire to the bottom of the plant.  A loose loop around the
stem under the first leaf axil will anchor the twine.  This twine
should have about 1-2 inches of slack.  As the plants grow and
during suckering, the plants twist around the twine and are
fastened to the twine using plastic clips.


PEST CONTROL.  Mulch with plastic, straw, sawdust, peanut hulls,
or ground corn cobs to help control weeds and reduce moisture
loss.  Mulches also reduce blossom-end rot and soil crusting or
packing.  Control of leaf mold, botrytis, and other foliage
diseases is essential.  Mosaic can be a serious problem.  Avoid
use of tobacco in any form while handling plants and while in
greenhouse.  Healthy plants should not be handled after handling
a diseased plant unless hands are thoroughly washed in milk.

Fruit worms, aphids, red spiders, leaf miners and/or white flies
may become problems.  Consult your county extension agent or the
current N. C. Agricultural Chemicals Manual for disease and
insect control recommendations.


WATERING.  Water control is important.  Check soil, 4-6 inches
deep, to determine when watering is necessary.  Water in the
mornings.  Do not wet the plant foliage.  When sidedressing is
needed wait until irrigation is necessary and "soak" the
fertilizer in with the water.  Drip irrigation with fertilizer
proportioners work well.  Overwatering is as bad as
underwatering.  Young plants don't require nearly as much water
as older plants.


POLLINATION.  Blossoms of greenhouse tomatoes will not set many
fruits unless they are pollinated.  Battery operated vibrators
are made for this purpose.  This is done by sharply vibrating
each flower cluster that has open blooms.  The vibration releases
the pollen which is necessary for pollination.  Pollinate at
least every other day and every day when blooms are numerous.
Best time to pollinate is 10:00 a.m. to 2:00 p.m. on sunny days.
Pollen does not shed on dark cloudy days and thus vibration will
be useless.  Blossoms that have not been pollinated turn brown
and drop off.  A portable air blower will also result in
sufficient pollination when directed on the plants in the
greenhouse.


HARVESTING.  Harvest when fruits are pink to red.  Handle
carefully to avoid bruising.  Most greenhouse tomatoes are sold
in 8 or 10 pound cartons, labeled "Greenhouse Tomatoes".  Ripe
greenhouse tomatoes will keep much longer than will field grown
tomatoes (14 days).  Never store harvested fruit below 55oF.


PROBLEM AREAS.  The following problems are often encountered by
greenhouse tomato growers:

 (1)    Soluble salts build-up in soils.  The soluble salts
        reading on your soil test report should be about 50-100.
        If the reading is above 125-150 problems with plant
        growth and blossom-end rot of the fruits often occur.

        To keep salts level low use fertilizers that don't build
        up salts.  Many growers mix their own preplant fertilizer
        to reduce soluble salt content since most ready-mixed
        fertilizers (like 5-10-10) tend to contribute to the
        soluble salt problem.  If salts are high, you can leach
        most of them with a heavy irrigation (up to 2 inches of
        water).

 (2)    Blossom-end rot.  Usually is due to lack of calcium. To
        reduce, be sure to apply proper amount of lime to supply
        the needed calcium. Some growers apply the recommended
        lime and then add an additional 25-50 pounds per 1000
        square feet of gypsum (calcium sulfate) before planting.
        Gypsum will supply calcium without affecting the soil pH
        and tends to improve the soil structure.  Fluctuation of
        soil moisture also results in blossom-end rot.
        Maintaining a uniform soil moisture supply reduces this
        problem.  Excessive sidedressing applied at any one time
        will also increase blossom-end rot.

 (3)    Blossom drop.  Blossoms fail to set fruit if: (a) they
        are not pollinated the day they open, (b) during
        continuous cloudy weather when the blossoms open, (c) the
        temperature is too high (above 90 F) or too low (below
        55 F) the day the blossom opens, (d) you have an
        application of too much nitrogen (particularly during
        cloudy weather), or (e) moisture content is too wet for
        optimum growth.

(4)     Spindly plants.  Usually caused by one or more of the
        following: (a) night temperatures are too high, (b)
        improper soil pH, (c) insufficient phosphorous, (d) too
        much shade or cloudy weather, (e) too much nitrogen
        during cloudy weather, (f) too much water, or (g) root
        problems such as nematodes.

(5)     Rough fruit.  Result from cloudy weather and/or
        temperatures too low during pollination.  Some varieties
        are more subject to rough fruit than others.  Many of the
        early and the large fruited varieties tend to have
        rougher fruits.

(6)     Fruit cracking. Some varieties are more susceptible than
        others.  Fluctuations in soil moisture results in more
        cracking.  Fruits exposed to full sunlight crack more
        readily, thus good foliage cover is essential.



SUMMARY.  Do all jobs completely and correctly.  Timing is
important.  Make out a time schedule for the entire year-- and
then follow it!  You can learn a lot by visiting someone who is
successfully growing greenhouse tomatoes.  If you don't know of
such a person contact your county agricultural extension agent;
he will help you locate one.  Be sure you know where you will
sell your produce BEFORE you plant.


                OTHER PUBLICATIONS FOR REFERENCE

(1) USDA Agr. Handbook No. 382, "Commercial Production of
    Greenhouse Tomatoes".

(2) Ohio Agr. Ext. Bulletin SB-19, "Growing Tomatoes in Ohio".

(3) Ohio Agr. Ext. Bulletin 674, "Greenhouse Tomatoes--Disease
    and Insect Control".

(4) American Vegetable Grower, Meister Publishing Co., 37841
    Euclid Ave., Willoughby, OH  44094.  (Monthly publication).

(5) Horticultural Information Leaflet Number 32-A, Greenhouse
    Vegetable Production List I.

(6) Horticultural Information Leaflet Number 32-B, Greenhouse
    Vegetable Production List II.

                            * * * * *