Ecophysiology of Cucurbits Crops:
Cucumber (Cucumissativis)
Climate
and soil requirements:
Cucumbers
grow best when the temperature ranges between 65 to 75oF (18 to 24oC) at a minimum
temperature of 60oF (16oC). When preparing for spring planting, the plants
should be started late enough to avoid prolonged temperatures below 55oF (13oC)
which can cause cold injury that is characterized by pitting, water soaked spots
and decay. In the piedmont region of the Mid-Atlantic, the healthiest crops
result from plantings made in May. The maximum temperature for good growth of
mature vegetative plants is 90oF (32oC). Later sowings (in late July) miss the
hottest weather during fruit production, but thevines are more vulnerable to
disease because of sustained higher humidity and temperatures, andbuildup of pathogens
in the environment.
Culture:
Culture
of cucumber is similar to that of fruit grown for market with two exceptions:
(1) another month is required to mature the fruit for seed – a growing season
of at least 100 days is required for most varieties; and (2), wider spacing is
needed – seedlings should be thinned to 12 to 18” within the row and spaced 6
feet between rows. When seeds are started indoors, the seed-starting medium should
be well drained and kept moist, not wet. Seed germination is inhibited at temperatures
below 60oF (15oC). The optimum is 95oF (35oC), though the temperature response
can vary significantly among varieties. Seeds are sown directly in the field or
as transplants not more than three weeks old.
Muskmelon
(Cucumismelo)
Climate
and soil requirements:
Melons grow best
in sandy loam soils well supplemented with organic matter. Such light, well
drained soils give earlier crops, though with reduced yields compared to clay
loam. Minimum soil temperature for direct seeding should be 65oF (18oC).
Transplants should be set out when the plants are about three weeks old. Soil
pH should between 6.0 and 6.7. Melon
seed germinates
poorly below 60oF (16oC). The optimum temperature range for germination is 75
to 95oF (24 to 35oC), with the germination optimum at 90oF (32oC). Muskmelon
grows best at moderately high air temperatures, the optimum range for growth is
70oF (21oC) and 95oF (35oC). Melons like other cucurbits, do not tolerate “cold
feet.” Root-zone temperatures (below 68oF (20oC)) make the plants more
susceptible to diseaseand less able to take up water due to a decrease in root
permeability. Even when there is ample waterin the soil, cold root temperatures
may injure the plant
Watermelon
(Citrulluslanatusvar. lanatus)
Climate
and soil requirements:
Watermelon
requires a long, warm growing season for fruit development and good yield.
Shorter season (65 to 75 day) varieties such as ‘Black Tail Mountain’ and ‘Sugar
Baby’’ do well in areas that have shorter growing seasons or at higher
elevations. Watermelon does best on a rich sandy loam, but will grow in most
soil types provided the soil is well drained. The plants are drought resistant
and prefer full sun, and hot, dry air. Humid, moist climates put the plants at greater
risk for disease, and for that reason, long periods of crop rotation in moist
climates are key for maintaining healthy crops. This is especially important in
seed production as many watermelon diseases are seed borne.
Culture:
Watermelon grown
for seed is grown in the same manner as watermelon grown for market, the main
difference being the row spacing. When grown for seed, plants should be spaced
24 to 36” within the row, in rows spaced at least 6 feet apart for short-season
varieties, and 8 to 12 feet or apartfor long-season varieties. The extra space
between plants will assist in determining which plant is mother to which fruit
during rouging. Because watermelon has an extensive root system, supplemental
irrigation is often unnecessary once the plants are well established. Watermelon
grows best at a soil pH of 5.6 to 7.0, but will tolerate a pH as low as 5.0. In
low pH soils, manganese toxicity can be an issue. The minimum temperature for
seed germination is 600F (160C) and the optimum is 950F
(350C). The optimum air temperature range for growth is between 75
and 860F (21 and 300C).
Effect on other stages
Roots
system:
The lateral
roots of all cultivated squash species are highly branched and grow primarily
in the upper foot of soil, and rarely below 2 feet deep. Some long-season
vining varieties will also develop taproots that can extend to a depth of 6
feet in loose soils. Many vining types (C. moschata and C.
argyrosperma) develop adventitious roots as the vines spread over the
surface of the soil. This growth habit confers additional drought tolerance and
resistance to vine borer. In some cases vines may be killed at their origin by
vine borers, but the plant may survive and produce fruit because of a large
number of root nodes along the length of the vine.
Harvest:
Squash fruits
are allowed to fully mature before being harvested for seed. If the fruit are
harvested at maturity, they should be allowed to after-ripen for at least 20
days before harvesting the seed. The after-ripening can occur while the fruits
are on the vine, with one exception. For example, in the South, where the
growing season is longer and the days are hotter, seed quality can decline
after peak maturity if temperatures are high and the fruits become sunburned.
Sunburned fruit can be an indication that seed may be damaged due to high fruit
temperatures. In a situation where sunburn can occur it is better to harvest
the fruits from the vine at maturity and then bring them under cover where they
can continue to after ripen before extracting the seed.
Seed extraction:
In large
commercial operations, fruit is mechanically crushed and macerated to release
the seed, or the fruits are cut in half and the seeds are scooped out by hand.
The seeds and pulp are put in a storage hopper and from there they are augured
into bins for transport to a shaker washer or onto rotating drum screens where
the seeds are sprayed with water.
Fermentation:
Fermentation is
a process that occurs naturally to some extent when fruit decomposes. When properly
done, fermentation helps to remove seed cleanly from the pulp, removes
germination inhibitors, and inhibits or kills certain disease organisms. The
usual length of fermentation depends on the temperature and the variety, but
typically the process is complete in about three days at a temperature of 70 to
75oF (21 to 24oC). High temperatures speed up
fermentation and low temperatures slow fermentation. When the fermentation
temperature is below 60oF (16oC) seed may be damaged. The
mash (mixture of seed and pulp) should be stirred at least twice daily
(preferably three times), to prevent the formation of mold on top of the mash
which may blacken or discolor the seed, thus reducing the quality of the seed
lot. During the fermentation process the seed separates from the pulp: the good
seed sinks to the bottom of the container and poor-quality seed floats to the
top. Good quality seed is dense and well filled out. Stirring the mash daily
also circulates nutrients through the mash, thereby aiding the fermentation
while allowing good seed to settle to the bottom of the container.
Drying:
Seed should be
spread out in a thin layer on screen-bottomed trays to dry in layers
approximately one seed thick. Air should be able to freely move through the
screen. Drying is best done under cover with forced air circulation. If the
temperature is mild and the air is dry, seeds may be sun dried, but if the
seeds are wet, the temperature should be below 90oF (32oC).
Seed may also be dried on cloth towels which help wick away the water.
Newsprint should never be used because the seeds may stick to the paper and the
ink will come off on the seed. Whatever method is used, the seed should dry as
soon as possible. The final seed moisture content ranges between 6 and 8%. Seed
with higher moisture content will not store well, and below 5% moisture content
seed may be damaged by over-drying.
Disease prevention and control
strategies:
Many
fungal diseases are encouraged by high humidity, use of overhead sprinklers
(especially late in the day leaving moisture on leaves), poor sanitation and
failure to remove crop residues, use of disease contaminated seed, failure to
use a minimum three-year crop rotation, and improper soil pH. Crops should be
located where the early morning sun can quickly evaporate the morning dew. Use
of cereal crops in the rotation scheme gives significantly better control than
rotation with non-cucurbit vegetable crops. By late summer/early fall, crop
residues should be removed as soon as possible and composted. Seeding a winter
cover crop helps to eliminate weeds and insects that harbor disease. Generally
recommended cover crops are annual or winter rye. The latter does a better job
of drying out the soil in the spring.
Presented
and prepered by:
Md. Rafiqul
Islam Shuvo
B.Sc.Ag.(Hons.)
, PSTU
MS in
Horticulture, BAU
www-agricultureinfo.blogspot.com
shuvo_ag10@yahoo.com
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