Subirrigation gravel culture growing bed

One problem which occurs in hydroponic growing systems is that pools of water form in the bottom of the growing bed container. These pools become depleted of oxygen very rapidly and if the plant roots extend into the pools the plants may die. This problem is solved by a false bottom (34, 54) in the growing bed container (10, 10'), so that any pooling which may occur occurs below the false bottom (34, 54). Pooling on the false bottom (34, 56) is prevented by the constructed of the false bottom (34, 56). The false bottom (34) either has a convex upper side, so that pooling cannot occur on the false bottom (34). Drainage openings (36) are provided at the two edges of the false bottom (34), so that any solution flowing towards the edges will flow through the openings (36) into the space below the false bottom (34). Or, the false bottom (56) is a sheet of formanous fabric material (56) which lies over a layer of gravel (54). During drainage the solution passes downwardly through the material (56) into the gravel (54) containing space below the material (56). No pooling can occur on the fabric material (56).

DESCRIPTION 
1. Technical Field 
The present invention relates to hydroponic growing systems, and in 
particular to the provision of an improved gravel bed container having a 
false bottom arranged to prevent pooling of water/nutrient solution in the 
growing bed space. 
2. Background Information 
A subirrigation gravel growing bed comprises a container, a bed of gravel 
within the container in which plants are grown, and inlet/outlet means in 
the bottom of the container. A water/nutrient solution is pumped into the 
inlet/outlet so that it will rise in the gravel bed up to a predetermined 
level. Then the pump is turned off and the solution is allowed to drain 
out through the inlet/outlet back to a reservoir. As the water drains out, 
fresh air containing oxygen is drawn down into the gravel bed and a film 
of nutrient is left on the gravel particles. 
Only a film of moisture on the gravel particles is desired. If puddles of 
solution remain in the bottom of the plant bed, poor plant growth results. 
Pools of solution become depleted of oxygen very rapidly and if the plant 
roots are allowed to grow into these pools the plant growth is adversely 
affected and over a period of time the plants may die. 
Hydroponic systems which exist in the patent literature and which include 
growing bed containers constructed from lengths of plastic tubing are 
disclosed by the following U.S. Pat. Nos. 4,185,414, granted Jan. 29, 
1980, to William M. Miller; 4,211,034, granted July 8, 1980, to Barry J. 
Piesner; 4,255,896, granted Mar. 17, 1981, to Vincent P. Carl; and 
4,310,990, granted Jan. 19, 1982, to Robert L. Payne. These patents should 
be carefully studied for the purpose of putting the present invention into 
proper perspective with respect to the prior art. 
DISCLOSURE OF THE INVENTION 
According to the present invention, a growing bed defining container is 
provided which includes a false bottom. The false bottom is located in the 
container above the container bottom, so as to define a space below the 
false bottom. The false bottom includes openings for allowing solution to 
flow between the spaces above and below the false bottom. The gravel bed 
is located above the false bottom and is constructed to prevent pooling on 
the false bottom. Water/nutrient solution intoduced into the space below 
the false bottom will flow upwardly through the openings in the false 
bottom into the gravel growing bed. During drainage, the solution flows 
back through the openings into the space below the false bottom. Any 
pooling of solution which may occur will occur in the bottom of the 
container below the false bottom. 
According to one aspect of the invention, the false bottom is a strip of 
plastic material having side edge portions which contact opposite bottom 
side portions of the container. The plastic materal includes openings 
which communicate the space below the false bottom with the space above 
the false bottom. 
According to another aspect of the invention, the opposite edge portions of 
the plastic strip material are notched at spaced intervals and the notches 
provide the openings which connect the space below the false bottom with 
the space above the false bottom. 
In accordance with yet another aspect of the invention, the false bottom is 
convex at its top and concave at its bottom, so that no solution will 
puddle on the central portion of the false bottom. 
In accordance with another aspect of the invention, the false bottom exists 
in the form of a sheet of foraminous fabric overlying a layer of gravel 
which sets on the bottom of the container. The fabric material includes 
openings which allows water/nutrient solution to flow both upwardly and 
downwardly through the material. Pooling cannot occur on the fabric 
material and any pooling which exists in the container below the fabric 
material is maintained out of contact with the plant roots by the fabric 
material. 
In accordance with yet another aspect of the invention, the growing bed 
container is formed from a length of plastic tubing closed at its ends, 
and said length of plastic tubing is supported in an elevated position by 
the use of a plurality of spaced apart concrete building blocks, set on 
end. The concrete building blocks have end recesses down into which 
portions of the plastic tubing are placed. The recesses are bordered by 
rough concrete edges which bite into and grip the plastic tubing, and 
effectively prevent the tubing from either rotating in position or moving 
endwise in position. 
Other more detailed features of the invention are described in the 
description of the preferred embodiment and are particularly pointed out 
in the appended claims.

BEST MODES FOR CARRYING OUT THE INVENTION 
FIG. 1 shows a plurality of growing bed forming tubes 10 elevated above a 
floor or ground surface 12 by means of the use of a plurality of spaced 
apart concrete building blocks 14. 
In a typical installation, a plurality of growing bed forming tubes 10 are 
spaced apart in a growing space, to provide a plurality of parallel 
growing rows. The tubes 10 are preferably lengths of plastic (e.g. PVC) 
pipe. In a typical installation, six inch diameter pipe is used. Slots 16 
are cut into the upper portions of the pipes 10, to provide upwardly open 
growing regions within the pipes 10. The pipes 10 may be closed at their 
ends by use of plastic end caps 18. 
The concrete building blocks 14 provide a very easy but effective and 
inexpensive way of supporting the pipes 10. The concrete blocks 14 measure 
eight inches by eight inches by sixteen inches. The blocks 14 are set on 
end. The end that is directed upwardly includes an end recess formed 
between two end portions 22. Concrete building blocks 14 have rough 
surfaces. As a result, when a length of tubing 10 is set down onto a pair 
of spaced apart blocks 14, with portions of the tubing 10 set into the end 
recesses 20, contact is made between wall portions of the tubing 10 and 
corner edges formed where the recess 20 meets the end portions 22. The 
rough concrete at these edges grips the plastic pipe 10 and keeps it from 
rotating or moving endwise relative to the blocks 14. The use of a sixteen 
inch block 14 places the tubes 10 at a very usable height above the 
ground. 
As is well-known, hydroponic growing involves the growing of plants in beds 
of gravel. Seeds or starter plants are spaced apart in the growing bed. 
Water containing a nutrient for the plant is introduced into the gravel 
and then allowed to drain out, leaving a film of nutrient on the plant 
roots and the gravel surrounding the plant roots. 
The subject system is a subirrigation system. This means that the water 
containing the nutrient is introduced through the bottom of the bed. 
Referring to FIG. 1, a manifold 24 is provided at one end of the growing 
space. Pipes 26 extend from manifold 24 to central bottom portions of the 
pipe 10. Water (e.g. from a reservoir 25) containing the nutrient is 
pumped into the manifold 24 and flows from manifold 24 through the pipes 
26 and inlet/outlet ports 28, into the lower portions of the growing tubes 
10. The water/nutrient solution is pumped at such a rate that the level of 
the solution will rise in the gravel bed 30. Once the solution reaches the 
upper regions of the pipes 10, the pump is turned off and the solution is 
allowed to drain back through the inlet/outlet ports 28 and the pipes 26 
into the manifold 24. As the water drains out fresh air containing oxygen 
is drawn in through the top openings 16 and a film of nutrient is left on 
the plant roots and on the gravel. 
Only a film of moisture on the gravel is desired. If puddles of solution 
were to remain on the bottom of the plant bed, poor plant growth would 
result and the plants might die. 
A principal aspect of the present invention is to provide for complete 
drainage of the solution away from the plant roots. 
According to the invention, the growing tubes 10 are provided with false 
bottoms so that if any puddles remain in the pipes 10 they will be below 
the level of the false bottom. In this manner, the roots of the plants are 
isolated from any puddles which might exist. 
Referring to FIG. 3, a first form of false bottom 34 comprises a strip of 
plastic material having opposite edges cut or otherwise formed to provide 
passageways. By way of typical example, each false bottom 34 may be a 
sidewall strip cut from the same type of pipe used for the growing beds 
10. 
FIGS. 3 and 4 disclose an example construction of the edges of the false 
bottom 34. This construction involves the formation of spaced apart 
notches 36 in the edges, leaving projections 38 between the notches 36. 
The false bottom strip 34 is set down into the bottom of the pipe 10, with 
its convex side directed upwardly. The projections 38 contact the bottom 
or valley of the pipe. The notches 36 provide avenues communicating the 
space 40 below false bottom 34 with the gravel containing space above the 
false bottom 34. Preferably, a foraminous fabric strip 42 (e.g. nylon 
organdy) is placed over the false bottom 34. The fabric material 42 allows 
the nutrient/water solution to pass through its pores or openings quite 
easily, but prevents the gravel in gravel bed 30 from plugging the 
openings 36. 
In use, the water/nutrient solution is pumped into the pipes 10 through the 
ports 28. The solution enters the space 40 and quickly flows lengthwise 
through the space. Next, the solution flows through the openings 36 into 
the space above the false bottom 34. It continues to rise in the space 
until either the pump is turned off or the level of inlet openings 48 into 
overflow pipes 44 are reached, whichever occurs first. The overflow pipes 
pick up whatever overflow may occur and delivers it to return pipes 46. 
The return pipes 46 empty into the reservoir 25 from which the solution 
was pumped. 
When the pump is turned off, the solution within the pipes 10 drains out 
through the opens 36 and the inlet/outlet ports 28. As will be apparent, 
if there are any puddles in the lower part of the pipe 10, they will be 
below the false bottom 34. As previously mentioned, the false bottom 34 
blocks the plant roots 32 from entering into whatever puddles might exist. 
The use of the false bottom 34 also provides a quite simple yet effective 
way of flow distribution. The first flow into the space 40 finds it easier 
to flow along the length of space 40 than to flow up and through the 
openings 36. This is because of gravity acting to hold the solution down 
and the open nature of the space below the false bottom and its relatively 
large size in comparison with the openings 36. Thus, the solution first 
fills space 40 and then flows upwardly through the openings 36, 
substantially uniformly along the full length of the tube 10. 
FIG. 5 discloses what may be a less expensive way of constructing a false 
bottom. A screen or other foraminous sheet of material 52 is provided on 
the bottom of each pipe 10, immediately over the outlet port 28'. A layer 
of gravel 54 (e.g. three quarters of an inch crushed gravel) is placed in 
the bottoms of the tubes 10 and then a foraminous fabric 56 is layed over 
the gravel 54 and at its edges is cemented to the plastic pipe 10. The 
spaces between the pieces of gravel 52 form a region in which any puddling 
that might occur will occur. The fabric layer 54 prevents the plant root 
32 from growing down into the region below the fabric layer 54. 
The concrete blocks 14 elevate the tubes 10, so that gravity return of the 
water/nutrient solution is possible. In commercial systems, either in 
greenhouses or out of doors, where the system is built on the ground, it 
only becomes necessary to level the ground below each concrete block. As a 
result, the set up time is low and the set up procedure is quite simple. 
The edges of the concrete material which contact the side surfaces of the 
tubing "bite" into the tubing and hold it securely in place.