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Green-house vegetable cultivation
By
Dr Adnan Younis & Dr M. Aslam Pervez
 Green-house
vegetable production is a highly intensive enterprise
requiring substantial labour and capital inputs. Because
of this, potential growers should carefully consider all
factors necessary for a successful enterprise.
In many ways, Green-house vegetable production is a
24-hour commitment. Its maintenance, crop production and
handling emergencies require constant vigilance. Every
4,000 square feet of green-house space requires an
estimated 25 to 30 hours of crop care and upkeep.
Green-house structures require constant maintenance and
repair. Many of the selected Green-house covers must be
replaced on a regular basis. Heating, cooling and
watering systems must be maintained and routinely
serviced.
In addition, contingency plans and backup systems must
be in place in case any of these major systems should
break down. Even a one-day loss of cooling, heating or
water during a critical period can result in complete
crop failure.
Along with the essential skills, capital and labour to
build, maintain and grow a crop, producers must develop
markets willing to pay the relatively high prices
necessary to make the enterprise economically viable.
Green-house-grown vegetables cannot compete with
comparable field-grown crops based on price; therefore,
green-house-grown vegetables often are marketed to
buyers based on superior quality and off-season
availability.
Finally, the personality and skills of the person or
people involved in the enterprise should be considered.
As mentioned earlier, this can be a 24-hour commitment.
If you don’t have the temperament to commit and to be
available day or night as needed, then this is not for
you. In addition, a successful green-house vegetable
production operation requires mechanical aptitude, crop
production skills and business acumen.
Although green-house production is an intensive
undertaking, it can be very satisfying and rewarding.
One advantage of green-house vegetable production is the
relatively small amount of area required compared with
field-grown produce. In addition, the return on
investment can be good if the requisite markets can be
found. Several vegetables have been successfully
produced in a green-house, including cucumbers,
tomatoes, peppers, lettuce, herbs and, by far the most
important, tomatoes.
Cucumber: Cucumbers generally grow more rapidly than
tomatoes and produce earlier. They also require high
temperatures which mean they are generally grown as a
spring or early summer crop. Daytime temperatures should
be 80-85°F and night-time 65-75°F. Soil temperatures
should be at least 65°F. Lower temperatures will delay
plant growth and fruit development.
Cucumbers are heavy feeders requiring 300-400 lb/acre of
P205. Similar quantities of potassium are required.
Weekly feedings with a balanced fertiliser (20-20-20)
will be required for maximum production. Never stress
seedlings for water or nitrogen.
Plants are best started in individual containers. As
seeds are often very expensive, sow one seed per
container (1/4 to 1/2 inch deep) in a sterile potting
mix with the spiked end of the seed up (root will emerge
facing down). Cover pots with clear polyethylene, and
place in the shade. Plants will emerge in two to three
days at 80-85°F. Remove plastic coverings when plants
emerge and place them in full sun.
After plants have formed at least two true leaves,
transplant them to their permanent location in the
growing bed. Cucumbers will require 6-8 square feet of
space per plant. Plants are generally spaced two feet
apart in rows three to four feet apart.
Tomato: One or two tomato crops can be planted in the
green-house during the year. Planting, transplanting,
and harvest dates will vary depending on location. As
most tomato varieties will begin to ripen 100 days after
planting, seed should be planted so the fruit begin to
ripen soon after first frost for fall crops.
Tomato crops are generally planted in early July and
transplanted to green-house beds in mid-August. Harvest
will begin in October and may continue until early
March. Harvesting may be terminated at an earlier date
if heating costs become extreme. Late spring harvest can
be accomplished by delaying planting until late fall or
early winter. Plants are best started in individual
containers (plastic pots, peat pots, or cubes) to reduce
labour costs and transplanting shock.
Use of commercial sterile potting mixes will decrease
the incidence of seedling disease problems. Custom soil
mixes can be used, but must be pasteurized to eliminate
insects, diseases, and weed seed.
Heating the moist soil mixture to a temperature of 160°F
for 30 minutes will kill most pests. Sow two to three
seeds per pot (1/4-inch deep) and water. Then cover pots
with clear polyethylene and place in the shade (70°F)
until seedlings emerge. Plastic should then be removed
and the pots moved into full sun. Thin the seedlings to
one plant per pot.
If possible, seedlings should be grown at daytime
temperatures of 58-60°F and night time 52-56°F for the
first 10-14 days. This initial cold treatment should
help seedlings develop larger cotyledons and thicker
stems. Plants should also set more early fruit,
increasing both early and total yields.
Thereafter, a daytime temperature of 70-75°F and night
time 60-62°F) should be maintained. After the initial
cold treatment, temperatures should not fall below 55°F,
which may cause rough, irregularly shaped fruit and
stunted plant growth. Temperatures can be reduced
slightly during cloudy days.
Irrigation water may have to be heated in the winter
before use. Water less than 50°F will chill the roots,
causing poor growth. Plants should be fertilised weekly
with a starter solution (1/2 ounce of 21-53-0 per gallon
of water) in the irrigation water. As plants become
larger, feeding can be increased to twice a week.
Transplants should be established in the ground beds
approximately four to six weeks after seeding. Set
transplants in the soil one inch deeper than previously
grown. Space plants 15-18 inches apart in rows 3-3.5
feet wide. Watering should be done immediately after
transplanting.
Lettuce: Lettuce is generally grown when light
intensities are low and temperatures are cool. Plants
prefer a daylight temperature of 60-65°F and a night
time temperature of 50-55°F. High green-house
temperatures will often result in spindly growth and
seed-stalk development in some varieties.
A crop of lettuce can be scheduled between fall and
spring tomato crops. Lettuce usually takes about one
month from seeding to transplanting. Days to harvest
from seeding may vary from 12-15 weeks in mid-winter and
from 8-10 weeks in early spring.
Under poor light intensities a 9 x 9-inch spacing may be
used, while a 6 x 6-inch spacing can be used in the
spring as light conditions improve. Lettuce is a poor
feeder, but requires a high level of nutrition. Apply a
balanced fertilizer before planting with weekly nitrogen
feedings as needed.
Courtesy:
Dawn |
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Pakissan.com;
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