A simple, foolproof system for veggie
production without circulation pumps
Non-Circulating Hydroponic Systems for
by Bernard A. Kratky , Hideo Imai, & James S.
[ PDF ]
US5385589 / US5533299
Non-circulating hydroponic plant growing system
The non-circulating hydroponic kit incorporates a water impervious
container capable of holding a variable depth of nutrient solution
and a solid container lid with a plurality of apertures through
which a multitude of root-impervious tubes or frusto-conical
containers can be inserted and supported. The lid stops visible
light from entering the plant holding container by fitting over
the container, and the reusable tubes can be of a multitude of
lengths. Preferred lengths are from 5 to 9 inches long. The tubes
have open tops and a plurality of apertures in the side walls,
preferably 1/4 to 1/2 inches in diameter. The tube may have a
plurality of vertical foils extending inward from the side wall
and downward to the lower end to deter roots from spiraling around
the side walls. Nutrient solution is placed in the container and
the tubes are filled with a particulate growing medium. At the
start of the growing period, the tubes are is immersed to a depth
of 1 to 2 inches in the nutrient solution which wets the
non-immersed media by capillary action. Eventually, the nutrient
level is lower than the bottom of the plant tubes, but the roots
are able to gather water and nutrients at this stage of growth.
Thus, only the initial application of nutrient solution is needed.
No additional watering or fertilization is needed. This system
works best with a short-term crop such as lettuce.
BACKGROUND OF THE INVENTION
The underlying principle of hydroponics has been used for hundreds
of years as a growing method for plants. Researchers in the 1800's
used the technique to determine the essential elements for the
growth of plants. Today, there are many hydroponic systems which
vary in complexity and cost.
According to a Gallup poll conducted in 1985, there is a trend
toward smaller scale gardening by consumers. The gardening
suppliers have met the demand by offering new types of containers,
special types of seeds and other products designed to make such
gardening easier. Factors that are contributing to the trend of
container gardening include:
1. The sale of new homes on small parcels of land is expected to
increase the trend of container gardening in the years ahead.
2. Smaller gardening areas are easily cared for by the aged.
3. Containers will be used in decorating the one and a half
million decks that are added to homes each year.
Several companies sell gardening kits that target the container
gardener. One such company offers a gift product line of gardening
containers that are attractively packaged and marketed
internationally. The kits wholesale for $6.00, retail for
approximately $14.00 and consist of a growing container and
medium, garden seeds and instructions.
Scientific supply companies sell a variety of experimental
hydroponic kits and experimental plant growing kits that are
marketed as educational tools.
A definite market exists for the hydroponic growing kit.
Non-circulating hydroponic systems which have a layer of screen
just above the nutrient solution level to encourage rooting
development and provide an anchor point for plant support are
known. A major disadvantage of those systems for a high density,
rapid turnover crop such as leaf lettuce (Lactuca sativa. L.) is
the difficulty of managing the nutrient solution level while
establishing the transplants.
There are many different non-circulating growing systems that have
been developed. The following is a sample of hydroponic systems
that can currently be found in patent and literature searches. The
sample excludes the many systems offered by laboratory supply
companies for sale to professional educators.
Net or Screen Planter
A PVC container holds a net bag with either vermiculite or smoked
rice husks (SRH) as a growing medium. The PVC container is placed
in a growing tank containing culture solution. Capillary action
draws nutrient solution to the plant.
Rockwool Cube Growing Container
A plastic lined plywood growing tank contains a layer of window
screening that provides root and plant support. The lid supports
rockwool cubes which contain the plant and absorb the nutrient
Plastic Pot Growing Container
A plastic pot containing smoked rice hulls is supported by the
tank lid. A net replaces the bottom of the pot to allow the
nutrient solution to be drawn from the polystyrene growing tank.
Pot Plan Nursery
Standard plastic pots or lattice pots filled with tuff were used
with non-circulating or circulating nutrient solutions. The
lattice pots were either supported by the floor of the tank or
were suspended in the solution.
Plastic pots containing media are immersed in a plastic lined tank
containing nutrient solution. The bottom of the corrugated tank
supports the pots. The polyethylene lid protects the roots from
direct sunlight and is painted white to reflect the sunlight to
Apparatus for Hydroponics (U.S. Pat. No. 4,794,728):
The apparatus consists of a box made of cardboard which contains a
water impermeable container. The container has at least one plant
support that protrudes through the opening of the lid. A plant
culture bed of porous solid medium is placed in the water
Indoor Multiple Purpose Hydroponic Cultivation Planter (U.S.
Pat. No. 4,735,036)
The planter consists of a leak-proof structure that has an upper
opening for insertion of a plant. A number of planters can be
coupled to each other via a side surface having a coupling
opening. The planters can be filled with porous grain fillers and
Planter, Especially for Hydroculture (U.S. Pat. No. 4,663,884)
This planter consists of a housing adapted to receive a pot that
is formed with a root compartment for a plant. The plates have a
space which communicates with the root compartment and is capable
of holding a body of liquid. A float apparatus is used to maintain
a constant liquid level.
Hydroponic Assembly and Wafer for Use Therein (U.S. Pat. No.
The planter consists of a trough containing nutrient solution and
a tray placed within the trough. The tray is interfitted with a
lid and has spaced openings serving as growing stations. A
compressed growing medium attached to a wick draws nutrient
solution by capillary action.
Horticultural Devices (U.S. Pat. No. 4,329,812)
This planter consists of an inner container made of fibrous
material that contains a growing medium. The inner fibrous
container is supported by a root impervious outer container. This
outer container extends into a second container that holds plant
sustaining liquid. That allows the plant to be readily removed
from the container.
SUMMARY OF THE INVENTION
The present hydroponic kit includes a storage container with
openings in a top to support tapered plastic tubes. Growing medium
is added to the tubes, and seeds are planted in the tubes and are
wet from the top. After 5 to 19 days, the tubes are placed in the
cover of the container, where the tubes extend down into a
nutrient solution which occupies approximately the lower half of
the storage container. In another embodiment, newly seeded tubes
are placed directly in the cover of the container. The growing
medium is supplied with nutrient solution by capillary action
through the portion of the tube immersed in the solution. As the
plants grow, roots spread into the solution, and the solution
drops below the bottom of the tubes. No further maintenance is
required until harvest.
No other hydroponic growing kits are closed systems for inserting
and holding tubes first partially submerged, and then spaced from
the nutrient solution without replenishment through harvesting.
The present invention is a simple hydroponic growing system. The
system uses easily acquired materials: a growing container with
lid, a root support system, a growing medium, seeds, and a
pre-measured batch of nutrients.
The kit can grow a wide variety of plants. Experimentation with
lettuce has provided the approximate quantity of nutrient water
needed to grow the lettuce without refilling the container, and
analysis of nutrient needs for a wide variety of plants shows that
other plants can be grown in the kit.
The hydroponic kit includes the following features:
A water impervious container capable of holding a variable depth
of nutrient solution;
a solid container lid with a plurality of apertures through which
a multitude of root-impervious tubes or frusto-conical containers
can be inserted and supported and which stops visible light from
entering the plant holding container by fitting over the
a reusable, root-impervious tube or frusto-conical container which
can be of a multitude of lengths, but is preferably 5 to 9 inches
long, which has an open top and an opening on the bottom of a
diameter equal to less than half of the diameter of the main shaft
of the tube, and a plurality of apertures in the side walls of
various sizes, preferably 1/4 to 1/2 inches in diameter. The
container may have a plurality of vertical foils extending inward
from the side wall and downward to the lower end to deter roots
from spiraling around the side walls.
The container is filled with a particulate growing medium. At the
start of the growing period, the tubular container is immersed to
a depth of 1 to 2 inches in the nutrient solution which wets the
non-immersed media throughout the tube by capillary action.
Eventually, the nutrient solution level may be lower than the
bottom of the tubular plant container, but the roots are able to
gather water and nutrients at this stage of growth. Thus, only the
initial application of nutrient solution is needed. No additional
watering or fertilization is needed. This system works best with a
short-term crop such as lettuce.
Pre-measured rates of a nutritionally complete fertilizer are
separately packaged and included in the kit, such that one packet
of fertilizer is added to the water at the beginning of each
growing cycle. The kit is able to accommodate a multitude of
growing cycles with replacements of only the particulate growing
media, a packet of fertilizer, seed and water.
While the growing kit could propagate plants on a large scale, the
following areas have great potential.
The kit may be used as an education tool. Educators may use the
kit to explain the process of plant cultivation and production
using hydroponic principles. It is a relatively low cost system
that educators can afford, and simple enough that they will not be
intimidated by it.
The kit may also be used as a gardening system. The kit is suited
to hobby gardeners, condominium tenants, and people who would like
to grow plants but who do not want to invest in gardening tools
and supplies. The kit contains everything needed to grow plants
and would not require anything other than the addition of water to
The growing kit is a relatively simple, low cost, self contained
system that requires little or no attention once the initial
planting has been done.
As with virtually all other hydroponic growing systems, the system
does not require treatment for soil-born pests or weeding.
The present kit does not require additional watering or
fertilization, nutritional monitoring, specialized equipment and
training, or electricity to operate aeration equipment.
One disadvantage associated with circulating hydroponic systems is
the potential spreading of root diseases to all plants contained
in the system. The problem is retarded in non-circulating systems.
It is even less of a problem in small non-circulating systems such
as the garden kit with only a few plants.
In an experimental model, a rectangular enclosure frame, 9.7
m.times.1.2 m, was constructed with 50.times.150 mm lumber at
ground level in a fiberglass covered greenhouse. Approximately 50
mm of soil from inside the enclosure was excavated and removed. A
tank was formed by placing two layers of 0.15 mm thick black
polyethylene over the frame. Sheets of 13 mm thick plywood coated
with white latex paint and reinforced with 19.times.64 mm lumber
(to prevent sagging) were placed over the frame. Holes, 38 mm in
diameter, were drilled in the plywood at 200 to 250 mm spacings.
Nutrient solution with a pH of 6.5 and an electrical conductivity
of 1.0 mS was added to the polyethylene tank. It consisted of a 75
mm depth of water containing the following (in mg/Liter): N, 93;
P, 33; K, 108; Ca, 110; Mg, 18; S, 23; Fe, 2; Mn, 1; Zn, 0.3; Cu,
0.3; B, 1; and Mo, 0.05. Fertilizer solutions included calcium
nitrate, potassium nitrate, potassium phosphate, sulfates of K,
Mg, Mn, Zn and Cu, and boric acid.
Leaf lettuce (`Green Ice`) was seeded in tapered plastic
containers, 40 mm diameter.times.218 mm deep, filled to the top
with 160 ml of a medium (1 sand: 0.6 peat: 0.4 vermiculite) and
watered by overhead mist in a seedling greenhouse. Care was taken
to pack the medium uniformly, thus eliminating voids in the
containers. The entire containers with 19-day-old seedlings were
transplanted into the plywood sheets such that 47 mm of the
seedling container extended above the surface and 158 mm remained
below the plywood sheet. There were ten 4 mm diameter holes in the
portion of the container located below the plywood sheet, four
oval holes (12 mm.times.4 mm) in the lower 20 mm of the container,
and a 7 mm diameter hole in the bottom of the container.
The bottom 25 mm of the containers was immersed in nutrient
solution and the resulting capillary action was sufficient to wet
the medium throughout the containers, thus automatically watering
the plants. No additional maintenance was required from this time
After a 32 day growing period, the average harvest weights of
lettuce from plant spacings of 200.times.230 mm, 200.times.250 mm
and 250.times.250 mm were 157, 188 and 195 g/head, respectively.
All heads were of marketable quality. In two other trials, lettuce
from 200.times.230 mm spacings yielded 176 and 187 g/head at 35
days after transplanting.
At the end of the growing period, 30 mm of nutrient solution with
an electrical conductivity of 0.5 mS and a pH of 7.5 remained in
the tank. The water consumption rate was 14.4 liters/kg of
harvested fresh weight of lettuce. In a simultaneous trial, the
water consumption rate for "Green Mignonette" semi-head lettuce
was 12.6 liters/kg of fresh head weight. Although the final
nutrient solution level was 20 mm below the bottom of the
containers, the media in the containers remained moist. However,
when the nutrient solution level was 40 mm or more below the
bottom of the containers, the medium in the tube was often dry.
Minimal root growth was observed from the 4 mm holes in the
containers located between the original nutrient solution surface
and the plywood cover. However, there was substantial root growth
from the bottom hole and the oval holes of the containers which
were immersed in nutrient solution at the start of the growing
period. A significant portion of that root mass emerged in a
conical form and was suspended in the air above the nutrient
solution. Remaining roots floated both on and into the nutrient
solution. Roots from adjacent plants intermingled with each other.
When the plywood cover was lifted during the growing period, roots
tore. Many roots suspended above the solution sank below the
nutrient solution level, causing the foliage to wilt or lose its
vigor. Thus, it is important not to disturb the plants while they
After leaf lettuce was transplanted in the capillary
non-circulating hydroponic system, no additional watering,
fertilization or monitoring of pH or electrical conductivity was
required. Thus, the only cultural operations required for this
system are: preparation of the nutrient solution, transplanting,
harvest, cleanup and, perhaps, disease or insect control.
The basic invention is provided as a kit and contains a storage
container with a lid, a bag of growing medium, four forestry
tubes, and two packets of fertilizer. Additional fertilizer may be
The user would fill the forestry tubes with damp growing medium,
packing it lightly by tapping the tube on a solid surface like a
table top to remove air voids in the tubes since they will prevent
capillary movement of water.
About 1.5 gallons of water (i.e. to a depth of about 4 inches) are
added to the storage container with one packet of fertilizer.
The tubes are placed in the cover of the storage container and the
seeds (1 or 2 seeds per tube) are planted at a depth of about 1/4
inch in the medium. For example, a leafy lettuce cultivar, e.g.
`Green Ice` is recommended Other short-term crops such as kaichoy
are preferable over long-term crops such as tomatoes.
The storage container is placed in a sunny area that is protected
from rain, such as under the overhang of a house, and left
undisturbed to avert tearing of roots.
If the container is almost dry (in about 4 weeks), more water
should be added, but only add about 1 quart or less at a time.
Adding too much water may cause the roots (which have now been
acclimated to being suspended in the air) to drown.
No extra fertilizer is needed in the closed system.
After the crop has been harvested, the container is washed with
water and the medium is emptied from the tubes into a plastic bag
and left to compost. That composted medium may be used for a third
crop. The tubes are refilled with the remainder of the medium
supplied with the kit, water and the other packet of fertilizer
are added to the storage container, seeds are planted and a second
crop of the year is under way.
This capillary, non-circulating hydroponic system appears to be a
promising technique for home gardening, and for teaching
situations where aeration or circulation cannot be easily
supplied. Lettuce has been successfully grown in tanks consisting
of buckets, large planting containers lined with plastic garbage
bags, insulated coolers, and old refrigerators lined with
It is preferable that containers and lids used be relatively water
tight, to maintain the closed system and allow receding of the
nutrient solution without replenishment from rain or watering.
The system of the present invention can be adapted to crops with
longer growing seasons and to select seedling containers which are
easier to fill or have other advantages. The capillary
non-circulating hydroponic system offers promising potential for
production of intensive crops, for home gardens, for educational
purposes and for growing plants used in research.
These and further and other objects and features of the invention
are apparent in the disclosure, which includes the above and
ongoing written specification, with the claims and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cutaway side view of the capillary,
non-circulating hydroponic system.
FIG. 2 is a side view of the bottom of the forestry tube
and a preferred relationship to the receding nutrient solution
DETAILED DESCRIPTION OF THE DRAWINGS
A preferred non-circulating hydroponic growing system of the
present invention is generally indicated by the numeral 1 in FIG.
1. The system or kit 1 incorporates a container 3, which may be a
bucket, cooler or similar article but can preferably be a three to
five gallon plastic, rectangular container when the system 1 is
sold as a kit. A cover or lid 5 covers the container 3. The cover
5 is preferably constructed of a material which blocks visible
light. Plural spaced tube-receiving apertures or holes 7 are
provided in the cover 5 for receiving growing tubes 9. The tubes 9
and apertures 7, and further the cover 5 and container 3, mate in
such a way so as to retard evaporation and prevent water from
entering the container during the growing season. The tubes 9 are
preferably tapered or frusto-conical in shape, and have open tops
10 at the larger end and root growing apertures 15 spaced from the
opposite root end 12. Growing medium 19 is packed into the tubes 9
during the initial planting period, and seedlings 16 or seeds are
planted therein. The root end 12 and at least one of the apertures
15 are initially submerged in a nutrient solution 11, which is a
mixture of growing nutrients and water. In a preferred embodiment,
the growing nutrients are specific to the type of plant to be
grown, and the amount of nutrients mixed with the water in the
solution 11 is sufficient to promote and sustain growth to full
In one experiment, "Green Ice" lettuce seedlings 16 were provided
with a nutrient packet of (in milligrams per liter): N, 93; P, 33;
K, 108; Ca, 110; Mg, 18; S, 23; Fe, 2; Mn, 1; Zn, 0.3; Cu, 0.3; B,
1; and Mo, 0.05. Fertilizer solutions included calcium nitrate,
potassium nitrate, potassium phosphate, sulfates of K, Mg, Mn, Zn
and Cu, and boric acid. The nutrient solution was mixed with
approximately 3 inches of water, forming a growing solution having
a pH of 6.5 and an electrical conductivity of 1.0 mS. Initially,
the solution is drawn through the apertures 15 into the soil and
to the seedlings' roots by capillary action. However, as the
growing season progresses (four to five weeks for lettuce), the
solution 11 drops below the root end 12 of the tube 9, as shown by
the right side of the system in FIG. 1. The roots 21 protrude out
of the apertures 15 while the water level is still above the
aperture, and as the level recedes, the roots follow and expand
throughout the container. The root systems proximal the apertures
are suspended in midair near harvest time to provide aeration
while the lower root systems are suspended within the nutrient
solution to draw nutrients therefrom. The root systems become
intertangled, and dislodging the lid 5 results in tearing in some
of the roots. Therefore, it is necessary for the lid 5 to remain
in place during the entire growing season of the plants.
Upon harvesting, the full grown plants 17 are removed from the
reusable tubes 9, and the water and debris is removed from the
container. The tubes are repacked with medium, the water and
nutrients are replenished, and a second growing season ensues.
In an alternate embodiment, the container 3 can be a plastic film
cradled within a wooden frame 13 or lining a hole of the
appropriate size which the user digs. In either case, the cover 5
can be a sized piece of plywood which fits over the top of the
excavation or frame, and which has plural spaced tube-receiving
apertures 7. In all cases, it is necessary for the water levels to
cover a portion of the tubes initially. It may then be allowed to
recede below the bottoms to provide aeration to the upper root
systems, yet still allow for suspension of lower root systems in
the nutrient solution, thus allowing adequate uptake of nutrient
In a preferred embodiment shown in FIGS. 1 and 2, the tubes are
plastic forestry tubes having top widths F of 40 mm and fitted so
as to extend above the cover 5 a distance C, which can be
approximately 45 to 50 mm. The root ends 12 preferably are
submerged in the solution 11 to a distance A, preferably about 25
mm, which covers at least one of the apertures 15. The original or
initial nutrient solution depth B in the container 3 is about 75
mm. A depth D of about 160 mm is provided between the cover and
the root end 12, which allows for a substantial amount of the
plant roots to be in contact with the medium. Spacing E between
tubes may vary according to the type of plant, as do the depths
and widths of solutions, tubes and submergences, but a preferred
spacing width is 225 mm for lettuce. A preferred ending nutrient
solution depth G is 30 mm, leaving 20 mm between the nutrient
solution and the root end 12.
The tubes 9 may incorporate vertical foils 22 to discourage
spiraling of the roots around the tube.
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