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Copyright 2005, Board of Trustees, University
Fort Pierce ARC Mimeo Report RL-1972-2
A "PLUG-MIX" SEEDING METHOD FOR FIELD PLANT TOMATOES
AND OTHER SMALL-SEEDED HILL CROPS/ JUN 5 1972
Norman C. Hayslip
I.F.A.S. Agricultural Research Center, Fo l e ce .
"Plug-mix" seeding refers to incorporating crop seeds and water into a
scientifically blended growing medium which is then precision placed in the
field at rates of 1/8 to 1/4 cup of loose mixture per hill.
During the 1970 and 1971 seasons over 2,000 acres of tomatoes and 300
acres of peppers were plug-mix seeded in south Florida through holes cut in
plastic mulch covered beds. These plantings were made as a result of 4 years'
research by personnel at the Agricultural Research Center, Fort Pierce, Florida.
All commercial plug-mix plantings were made using hand labor, but an auto-
matic plug-mix planter was recently developed and is now available to growers.
This planter will greatly reduce the labor costs, making this method of seeding
an economical practice for crops with larger plant populations and/or lower per
acre dollar value.
Because of growing interest in the plug-mix seeding technique, and its
outstanding success in experimental and commercial trials, the following
information has been prepared for those wishing to make test plantings on
Advantages of plug-mix seeding over standard seeding methods
1. Provides a uniform, optimum environment in seed and young seedling
zones with an adequate, safe level of fertilizer readily available
to the seedlings.
2. Plant stands are often better, and seed germination and plant growth
3. There is no compaction problem with the friable plug-mix soil.
4. Reduces fertilizer salt damage during dry periods, and lessens
leaching of nutrients during top-watering and rainfall.
5. Conserves fertilizer and seeds by placement only where needed,
thereby reducing the fertilization of competing weeds.
6. With the new automatic plug-mix planter an economical and highly
successful method of seeding through mulch covered beds is now
1/ A revision of Mimeo Report 71-2, March, 1971.
Reference to trade names of materials
and equipment does not constitute an
Formulation of plug-mix for tomatoes, using 1 cup per hill
For 600 hills For 1800 hills
Cornell Peat-Lite Mix ............One bushel.........One 4 cu. ft. bag
** Magamp, 7-40-6 (med. granule)..... pound............1 pounds
Tomato seeds..................... ounce........... ounces
Water (to slightly moisten........3 to 4 qts.........9 to 12 qts.
Developed by J. W. Boodley and R. Sheldrake, Jr., Cornell University.
Contains a 1:1 mixture of shredded sphagnum peat moss and horticultural
vermiculite with nutrients added. Commercially available as "Jiffy-Mix",
"Redi-Earth", and possibly other trade names.
** Magamp has been blended into the Peat-Lite mix and marketed as "Jiffy-Mix
Plus". Check with supplier to determine if Magamp has already been added.
The Cornell Peat-Lite, Magamp (if not added by supplier), and tomato seeds
are mixed dry for 5 minutes or more in a tumble-type cement mixer. Mixer drum
should be tilted almost to the point of discharging to insure complete mixing.
A removable cover should be placed over the mixer opening to hold down dust.
Clean water is added slowly while the mixer is running. Mixing is continued
for 5 minutes or more after the water is added. Any balls of mix larger than
a marble should be broken up by hand or by dumping through a coarse screen.
Since different lots of the commercially available mix seem to vary in
moisture content, the recommended rate of water listed above may need to be
adjusted. It is desirable to add as much water as is possible without
creating a sticking problem in the plug-mix machine; however, adding too much
water will definitely create application problems.
The seed-soil-water formulation can be stored for 2 days before use (longer
during cold weather). Field planting should be done before the seeds begin to
germinate. One bushel of mix will plant about 600 hills, using the recommended
1/4 cup of loose plug-mix per hill. Most hills will have 2 to 10 tomato plants,
averaging 5 to 7 per hill. Some tests have indicated little or no difference
in benefits between 1/8 cup of mix per hill and the 1/4 cup rate. If 1/8 cup
is used, the amount of seed per bushel or bag of mix would be twice that
recommended for the 1/4 cup rate of application.
Application of plug-mix
An automatic "soil or plug-mix" planter was developed by Mechanical Trans-
planter Company, Holland, Michigan especially for applying plug-mix, and is
available to growers. This new machine was tested in both sandy and rocky
soils of south Florida, in both mulch-covered and unmulched beds, and with
tomatoes and peppers. The tractor mounted automatic planter meters up to
1/2 cup of loose mix into revolving cups which deliver the mix to the planter
pockets. The pockets pierce the soil and deposit the mix at fixed intervals.
Press wheels are mounted behind planter pockets. The unit works well on mulch
covered beds, the pockets punching holes through the mulch as they deposit the
mix. The tool-bar mounted planter has operated efficiently at a forward speed
of one mile per hour, regardless of plant spacing, and is designed to plant at
down-row spacings of 10, 12, 15, 20, 30 or 60 inches. Some growers plan to
mount two planters to a tractor for seeding two rows of tomatoes. With 2
planters it should be possible to seed 8 to 10 acres per day at 5' between-row
spacings. With one planter and rows spaced 7' apart, 5 to 7 acres per day
can be planted. Since planting depth is regulated by the planter tires and
tractor tool-bar this machine is not adapted to irregular bed heights as
A simple and inexpensive hand operated applicator was constructed for use
in early research trials. The pluggerss" were used by some growers with good
results, but labor costs were rather high. This applicator is recommended for
those wishing to make small scale tests. Details on the hand plugger can be
obtained from the author.
Other growers have constructed hole cutters for mulch covered beds which
make a hole about 1 to 2 inches deep at the time the holes are cut in the
plastic or paper mulch. Workers then apply the mix in these holes, using ice
cream scoops. This system requires less labor than the hand plugger, but is
recommended only where the automatic plug-mix planter cannot be used.
The accumulation of excess fertilizer salts at the exposed soil surface
in holes cut through plastic covered beds has resulted in serious damage to
seeds and seedlings. This problem is worse during periods of hot weather and
low rainfall when evaporation is rapid. In most experiments the standard
method of seeding tomatoes (direct-seeded into the bed through holes in plastic)
has been unsuccessful during August and September. Plug-mix has given good
protection by buffering the damaging effects of these salts, but injury can
occur even with plug-mix seeding if the salts become too concentrated.
Watering studies have shown that during hot weather with no rainfall it
is necessary to apply top-water every 2 days until the tomato plants are well
established. The water moves the salts down and away from the seeds and young
seedlings, while maintaining good moisture conditions. The use of sprayer
tanks with nursery type nozzles over each row is an effective method of
watering. Over-head watering may not be necessary, except to keep the plugs
moist, on tomato crops grown on beds without plastic mulch where less ferti-
lizer is used.
Plug-mix seeding cost for materials and seed would be approximately 1/2
cent per hill for the 1/4 cup rate or 1/4 cent for the 1/8 cup per hill rate.
Application cost, using the automatic planter, would be about $8.00 $12.00
per acre. For both materials and planting the cost would be from 1/2 to 3/4
cent per hill at the 1/4 cup per hill rate, depending upon plant population.
Per acre plant population of 10 to 20 thousand would cost approximately 1/2
cent per hill; populations of 3,000 or less would cost about 3/4 cent per hill.
Use of plug-mix for other vegetable crops, and seedbeds
Although most research has been with tomatoes and peppers, the plug-mix
system has definite promise for other small-seeded vegetable crops such as
cabbage and eggplant. Limited trials in which the mix was drilled in con-
tinuous bands have shown promise for seedbeds. Plant stands have been better
and growth more vigorous and uniform where this seeding technique was com-
pared with standard seeding methods. Tests with onions and carrots indicate
better and more uniform stands can be obtained by drilling the soil-mix.
However, the cost may be prohibitive due to the larger volume of soil-mix
required. for drilling in a continuous band.
Plug-mix applicator designed for research trials. Worker on left dumps
% cup of soil-seed mix into side funnel. Second worker then lowers
plunger to compact and force mix into plant bed.
Plug-mix seeded hill in plant bed. The mix is compressed into a plug
1/2" in diameter and 1" thick.
6 jk4*.. .It.
Automatic plug-mix planter travels about one mile per hour while
precision spacing plug-mix hills at 10; 15; 20; or 30 inches down-row.
Automatic plug-mix planter punches rectangular hole in plastic mulch
and deposits the seed-soil mix in this hole. Note even germination of