The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
i J IDP Fort Pierce ARC Research Report RL 1974-3 March, 1974
Q A "PLUG-MIX" SEEDING METHOD FOR FIELD PLANTING TOMA
AND OTHER SMALL-SEEDED HILL CROPS/
Norman C. Hayslip
I.F.A.S. Agricultural Research Center,,.'rt Pite '
"Plug-mix" seeding refers to incorporating crop seed's6ad wat e nto
scientifically blended growing medium which is then precisis 'laced n the /
field at rates of 1/8 to 1/4 cup of loose mixture per hill. O/ /t
During the 1970 and 1971 seasons over 2,000 acres of tomatoes'.afd.3
acres of peppers were plug-mix seeded in south Florida through holes ct' in
plastic mulch covered beds. This seeding method has increased to about
10,000 acres in Florida during the 1973-74 season.
At first, commercial plug-mix plantings were made using hand labor, but
automatic planters were developed and are now used by most growers. The planter
reduces labor costs, making this method of seeding as economical practice for
crops with larger plant population 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 plantings on their
Advantages of plug-mix seeding over standard seeding methods
1. A uniform, optimum environment in seed and young seedling zoneS,
with an adequate, safe level of fertilizer readily available to
the seedlings is provided.
2. Plant stands are often better, and seed germination and plant growth
are more rapid and uniform.
3. There is no compaction problem with the friable plug-mix soil.
4. Fertilizer salt damage during dry periods, and leaching of nutrients
during top-watering and rainfall are reduced.
5. Fertilizers and'seeds are conserved by placement only where
needed. This reduces the fertilization of competing weeds.
6. With the automatic plug-mix planter an economical and successful
method of seeding through mulch covered beds is now available.
Reference to trade names of materials
and equipment does not constitute an
1/ A revision of Mimeo Report RL-1972-2.
Formulation of plug-mix for tomatoes, if using C 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............11 pounds
Tomato seeds................... ounce............l 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, a co-granulated magnesium ammonium phosphate and magnesium
potassium phosphate, 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 can be mixed dry for 5 minutes or more in a small 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 while the mixer is running.
Mixing is continued for 5 minutes or more after the water is added. Balls of
mix larger than a marble, if present, can be broken up by hand or by dumping
through a coarse screen. Several growers use large ready-mix concrete mixers,
formulating about 50 bags (200 cu. ft.) at a time. One grower reported each
batch requires about 25 minutes mixing time. Since mixers differ, each grower
should determine his best system for adding seed and water.
Because different lots of the commercially available mix may 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 tomato seed-soil-water formulations can be stored for 2 days before
use (longer during cold weather). Field planting should be done before the
seeds germinate. One bushel of mix will plant about 600 hills, using the
recommended 1/4 cup 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.
Formulation of other vegetable seeds should be similar to that for
tomato. A table (page 4) has been included as a general guide in determining
the amount of seed to be added to a 4-cubic-feet bag of mix.
Application of plug-mix
An automatic planter was developed by Mechanical Transplanter Company,
Holland, Michigan especially for applying plug-mix, and is available to
growers. This machine was tested in both sandy and rocky soils of south
Florida, in both plastic 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 can be mounted behind planter pockets to firm the soil from each
side on unmulched beds. The unit works well without press wheels on mulch
covered beds, the pockets punching holes through 4~h- mnich as they deposit
the mix. The tool-bar mounted planter has operated efficiently at a forward
speed of one mile per hour, and is designed to plant at down-row spacings of
10, 12, 15, 20, 30 or 60 inches. Some growers have mounted two or three
planters to a tractor for multiple row seeding. With a 2-row planter it
should be possible to seed 10 to 12 acres per day at 5' between-row spacings.
With one planter, and rows spaced 7' apart, 6 to 8 acres per day have been
planted. Since seed depth is regulated by the planter tires and tractor
tool-bar, the original machine was not adapted to irregular bed heights.
However, an attachment was made to provide flotation at the front of the
planter which greatly improved uniformity of planting depth. This flotation
attachment is now available from the manufacturer and should be considered
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.
Some growers have constructed cutters for mulch covered beds which make
planting holes about 1 to 2 inches deep at the time the holes are cut through
plastic or paper mulch. Workers then apply the mix in these holes, some using
ice cream scoops. This system required less labor than the hand plugger,
but is recommended only where the automatic plug-mix planter cannot be used.
One pepper grower built a machine which cuts holes through the mulch covered
beds and delivers a continuous band of the mix on the bed center. Brushes
sweep the mix into the holes.
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 plast.n)
has been unsuccessful during August and September. Plug-mix has given some
protection by buffering the damaging effects of these salts, but injury will
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 either nursery or flood-jet 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 fertilizer is used. However, the plug-mix seeded hills must be kept
moist until the seedlings are established.
-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, should 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 and commercial uses have been with tomatoes and
peppers, the plug-mix system has promise for other small-seeded vegetable
crops. Limited trials in which the seed-soil mix was drilled in continuous
bands have shown promise for seedbeds, resulting in better plant stands and
more vigorous and uniform growth than obtained with standard seeding methods.
In tests with onions and carrots better and more uniform stand were obtained
by drilling the seed and soil mixture as compared to standard seeding methods.
However, the cost may be prohibitive due to the larger volume of soil-mix
required for drilling in continuous bands.
AMOUNT OF SEED REQUIRED TO OBTAIN AN AVERAGE OF ABOUT 4, 6
OR 8 SEEDS IN EACH 1/4 CUP OF LOOSE MIX PER HILLi/
Approximate Amount seed (ounces) for 4 cu. ft. bag mix
No. of Average Average Average
CROP seeds per ounce_2/ 4 seeds/hill 6 seeds/hill 8 seeds/hill
Broccoli 9,000 0.8 1.2 1.6
Cabbage 8,500 0.9 1.4 1.8
Cauliflower 10,000 0.7 1.0 1.4
Cucumber 1,000 7.2 10.8 14.4
Eggplant 6,000 1.2 1.8 2.4
Lettuce 25,000 0.3 i 0.4 0.6
Okra 500 14.4 21.6 28.8
Pepper 4,500 1.6 2.4 3.2
Tomato 11,000 0.7 1.0 1.4
1 / An average of fewer than 4 seeds per hill may result in excessive skips.
For a near-perfect stand an average of 6 or more seeds per hill may be
necessary. Figures are based upon 1800 hills per 4 cu. ft. bag of mix.
2 / From "Handbook for Vegetable Growers" by James Edward Knott.
Thirteen-day-old tomato seedlings plug-mix seeded with automatic
planter through black plastic covered bed. Note rectangular holes
in mulch and uniform seedling growth.
Pluge-ix (left) reduced leaching during heavy rainfall.
Right; check plot seeded directly $Sto sandy soil. Note difference in
size and uniformity of tomato plat4q, Black paper placed over one row
Effect of plug-mix and top watering on tomato seedling survival and growth. All plots
1. Standard seeded no top water after planting.
2. Plug-mix seeded no top water after planting.
3. Standard seeded 1/3 cup water/hill each 2 days.
4. Plug-mix seeded 1/3 cup water/hill each 2 days.
Plug-aix applicator daitged
for experimental plot work.
Top left; worker dumps mix
into side fu~nel. Top right;
center plunger campacts mix
ad drivei it into plant bed
through hole in plastic.
Lover left; plug is i"
diamter ad 1" thick.
This 50-bag (200 cu. ft) capacity mixer is
located on a tomato and pepper farm near Jupiter,
Top watering tomato seedlings through planting
holes in plastic mulch covered beds to prevent
excessive fertilizer salts from accumulating.
Note flood-jet nozzles mounted beneath the tractor
delivering water to 3 rows from 500-gallon trailer-
IFAS modifications of automatic
plug-mix planter. Top left -
floating front end with guage wheels
for improved planting depth control.
Top right press wheel attached to
rear axel. Bottom left over-all
view of planter with modifications
One-row plug-mix planter with front flotation and
guage wheel for planting depth control, and rear axel
Mounted press wheel. Note tool-bar mounted mix carrier
alongside planter. Forward speed is about one mile per
This 2-row plug-mix planter is self-steering,
requiring only one operator to plant 12 1/2 acres
per day. The square tanks supply water to the
automatic water applicators.