Download Nursery Management and Seedling Production

Prepared by:
Nercy M. Alvarado
The first step in successful vegetable
production is to raise healthy vigorous seedlings.
Young plants whether propagated from seed or
vegetatively require a lot of care particularly
during the early stages of growth. They have to
be protected from adverse temperatures, heavy
rains, drought, wind and a variety of pests and
diseases. If small seeded vegetables are sown
directly in the field, germination is often poor
and the young plants grow very slowly and
require a long time to mature. Also the season
may be too short for full development in the
field.
To overcome these problems many vegetable crops
are grown in nurseries before being transplanted in the
field. A vegetable nursery is a place where plants are
cared for during the early stages of growth, providing
optimum conditions for germination and subsequent
growth until they are strong enough to be planted out in
their permanent place. A nursery can be as simple as a
raised bed in an open field or sophisticated as a glasshouse with micro-sprinklers and an automatic
temperature control system. Although raising seedlings
in a nursery has advantages, some vegetables do not
transplant well, particularly root crops, and must be
sown directly in the field for optimum results. It has to
be noted, however, that transplanting seedlings
interrupts their growth, which has the potential to
reduce their vigor.
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Although many vegetable seeds can be
sown directly in the field, experience has
shown that raising seedlings in a nursery has
a number of advantages as discussed below.
1. Intensive care - Seedlings receive better care
and protection (from animals, weeds and
pests) in the nursery. The average garden soil
is not an ideal medium for raising seedlings
especially from the point of view of soil tilth.
At an early stage of development most
vegetable crops require special attention that
is not possible in the main field.
2. Reduction of costs - Fewer seeds are used for
raising seedlings in the nursery than for
sowing directly in the field, because in the
latter seedlings have to be thinned to one,
which is wasteful. When expensive hybrid
seeds are used, transplants therefore become
more economically attractive. Pesticides and
labor are also reduced under nursery
conditions as compared to planting directly in
the field.
3. Opportunity for selection - Raising
seedlings in a nursery affords the grower
an opportunity to select well grown,
vigorous, uniform and disease free
seedlings.
4. Extend a short growing season for late
maturing crops - Seedlings can be raised
in a nursery under a protected
environment before conditions outside
become suitable for growth and
transplanted into the field when
conditions allow, thus reducing the
amount of time spent in the field.
5. Forced vegetable production for an early
market - Generally prices of horticultural
produce are attractive when production or
supply is low. Vegetables can be grown ‘outof-season’ in a nursery when conditions are
not yet favorable. Such crops will thus
mature earlier after transplanting and hence
stand to fetch a higher price in the market.
There are three main facilities normally used
for raising seedlings in a nursery. The choice
of a particular one will depend on the
available resources and prevailing
environmental conditions.
* Greenhouses - environment fully controlled
* Net house - environment partially modified
* Open field - where climatic conditions are
normally favorable for the crops grown.
Seedling management
1.) Watering.
The seedbed or seed box should be
watered carefully with a fine stream of
water. After the plants are well established,
watering should be done thoroughly but not
too often. It is advisable to irrigate seedlings
in the morning and not in the afternoon as
the latter leaves the soil surface moist
overnight, a condition favoring damping off.
2.) Shading.
Shading should be done to protect the
young seedlings from high heat intensity
in sunny areas and also from heavy rain.
Shade can be provided by polythene nets
or even grass. The shade should be
removed some days before transplanting
to allow the seedlings to acclimatize to
field conditions.
3.) Thinning.
This is a way of regulating plant
density in rows and in holes. During
thinning, weak, diseased plants are
pulled out to allow healthy seedlings
to grow well. It is normally done
when seedlings have formed a few
true leaves.
4.) Insect pest and disease control.
This is a continuous process from
seedling emergence to transplanting.
It is normally done by physical
means but chemicals can also be
used if the need arises.
5.) Weeding.
This is done by physical means when
weeds emerge.
6.) Hardening-off.
Transplants must be ‘hardened-off’ so that they
can withstand the transition from a relatively
sheltered and protected environment to a sometimes
harsh open situation. Generally, hardening is
imposed from about 1 to 2 weeks prior to
transplanting seedlings, by gradually exposing them
to higher (or lower) temperature and the higher
light intensity prevailing in the field. It should,
however, not involve any treatment that may reduce
the rate of photosynthesis, such as nutrient stress.
Care should be taken not to over-harden plants, as
this may delay maturity and in some instances even
reduce crop yields.
7.) Transplanting.
This refers to the operation of lifting the
seedlings from the seedbeds or containers and
transferring them to the field where they will
grow and mature. The main aim during
transplanting should be to interrupt growth
as little as possible, and if the operation is not
carried out properly it can severely check
growth or in extreme cases cause death of
transplants.