Midwest Vegetable Guide - 2022 - 24

Transplant Production
In general, peat type containers are the most expensive,
followed by the Todd planter type, then the polystyrene type.
The number of plants in a tray depends on the cell size for
each plant. Vegetables are commonly grown in trays with 30
to 300 cells. In general, larger cells lead to greater early yield
in fruiting crops. Larger cells are also easier to manage
because the greater soil volume holds more water and
nutrients. Due to the expense of building and maintaining
greenhouse space, many growers have moved to smaller cell
volumes so more transplants can be grown in the limited
space available. Some growers use two different cell sizes: a
larger size for crops they expect to harvest earlier, and a
smaller size for crops they expect to harvest later.
Seeding and Growing
Most vegetable transplants are sown one seed per cell. As a
general rule, plant vegetable seeds at a depth two times their
diameter. Vegetable seeds temperature requirements vary;
most vegetable seeds germinate in the 70°F to 90°F range.
The time from seeding to transplanting varies from three to
four weeks (e.g., cantaloupe) to 10 to 12 weeks (e.g., celery).
Vegetable seed may be ordered with special features,
including seed priming and pelletizing. Primed seeds have
been partially hydrated, then dried down, resulting in earlier
germination and better uniformity. Priming may be useful for
hard-to-germinate seed such as triploid watermelon. Seed
may be pelletized to make it easier to handle. In this process,
varieties with small seeds, or irregular seeds (such as lettuce)
are coated to make the seed larger and uniform in size and
shape. This process makes mechanized planting easier.
The growing mix should be well-drained and free of diseasecausing
organisms (pathogens). Most commercial mixes fit
this description and perform well. These mixes are often
referred to as " soilless mixes " since they are composed
primarily of peat or coconut coir, perlite or vermiculite, and
sometimes bark or ash. These mixes usually come in bales or
bags and have been pasteurized (sufficiently heated to kill
soil microorganisms capable of causing disease problems). It
is advisable to test the mix before using it to make sure the
pH is within an acceptable range (between 5.5 and 6.5) and to
determine the initial nutrient content of the mix.
Most mixes include a small amount of fertilizer, but
transplants usually benefit from additional regular nitrogen
(N), phosphorus (P), and potassium (K) fertilization once true
leaves appear. Depending on the initial nutrient level in the
mix, including calcium (Ca) and magnesium (Mg) in the
fertilizer solution may also be advised. Soluble synthetic
fertilizers (21-5-20, 20-10-20) and liquid organic fertilizers
(e.g. fish emulsion) are commonly used. The best rate,
frequency, and method of fertilization will depend on your
potting mix and watering practices. Common alternatives
include a 50 to 200 ppm N solution applied at every watering,
24
or a 300 to 500 ppm N solution applied weekly. Mixes that
contain significant amounts of compost may not benefit from
additional fertilizer until several weeks into transplant
growth.
To make a 100 ppm N solution, use 0.42 pounds (6.6 ounces)
of a 20 percent nitrogen fertilizer for every 100 gallons of
water, or 4 fluid ounces of a liquid fertilizer containing 3
percent nitrogen for 10 gallons of water. Over-application of
ammoniacal N can be detrimental to transplants. This
problem can be minimized by not over-applying N, and by
using fertilizer in which most N is in the nitrate form. Check
the bag label.
Transplants that are too tall and tend to fall over are often
referred to as " spindly, " " shanky, " or " leggy. " Such
transplants may have low survival rates in the field. Spindly
transplants are produced under low light conditions, high
fertilizer rates, and/or overwatering. Cloudy weather or
greenhouse structures that don't let in adequate light could be
the culprits. Artificial lights could be helpful during
inclement weather, but may be cost prohibitive.
Under such conditions, use a fertilizer containing a lower
percentage of P. For instance, try 21-5-20 rather than 20-2020.
It is important to provide adequate P, but not too much.
Under fertilization with P will produce short plants, but yields
also will suffer. Hot days and cold nights favor leggy
transplants. If night temperatures are equal to or higher than
day temperatures, stem elongation will be reduced. It may be
sufficient to lower the temperatures for a two-hour period
starting at dawn.
To prepare transplants for the harsher environment of the
field, it is necessary to harden them off. Transplants may be
hardened off by withholding water and lowering temperatures
moderately during the last week or so of growth. Some
growers place transplants in wagons and wheel the
transplants outside on appropriate days to get the plants used
to field conditions. The transplants are wheeled back inside at
night and during especially harsh weather.
After transplanting, plants should be irrigated as soon as
possible. Some transplanters are equipped to irrigate plants at
the time of transplanting. Otherwise, arrange to irrigate soon.
Applying a small amount of starter fertilizer in the transplant
water is often beneficial. If transplants are held in the
greenhouse to replace those that don't survive, remember to
avoid using transplants that have begun to vine or flower.
Diseases
Diseases that are likely to affect vegetable transplant
production in the Midwest fall into two types: damping- off
diseases (caused by soilborne fungi) and transplant diseases
(usually associated with fungi, bacteria, or viruses that
survive with seed or plant residue). These diseases can cause
extensive transplant loss.
Midwest Veg Guide 2022
Midwest Vegetable Guide - 2022

Table of Contents for the Digital Edition of Midwest Vegetable Guide - 2022
