ABSTRACT
Chapter 12 exemplified individual unit systems� This chapter shows how to construct a series of pots, gutters, slabs, and so on that drain to a central reservoir� These growing systems are more complex in their construction due to the need for supporting structures for the growing trays and more plumbing to connect them to the feeding and draining systems� Some of the systems are more suitable to low-profile plants such as lettuce, arugula, basil, and herbs, while others are more versatile and can also grow vine crops such as tomatoes, peppers, cucumbers, and eggplants�
This system is the same principle as the single-pot wick design, but instead of just one pot a series of pots are supported in the lid of the nutrient solution reservoir (Figure 13�1)� This system is for low-profile crops� Use 4″ diameter plastic pots to contain perlite and/or vermiculite as the substrate� These pots are supported by the lid of the nutrient tank� Drill approximately 3¾″ diameter holes in the lid at 6″ × 6″ spacing� Be sure to measure the diameter of the pot directly below the lip so that the top lip section of the pot remains above the lid�
A second method is to place a grow tray on top of the nutrient solution tank and extend wicks from the solution tank through the base of the grow tray into the substrate of the grow tray where the plants are positioned, as was presented in Figure 12�3�
1� Storage bin with a snap-on lid 2� Cotton or fibrous nylon rope 3� Four-inch diameter plastic pots 4� Perlite and vermiculite mixture at half and half of each 5� Air pump and 4″ airstone
Drill the holes for the pots in the lid staggering their positions� If a large storage bin greater than 12″ × 18″ is used, reinforce the lid by placing a ¼″-thick plastic sheet on top and drill the holes at the same time through it and the lid to line them up
correctly� Without this additional support, the thin lid of the reservoir storage bin will sag and possibly break with the weight of the medium and plants�
Make a 2″ square access panel at one corner of the lid to add water and/or nutrients� This can also be the entrance of the poly tube from the air pump to the airstone within the reservoir�
Flare the ends of the rope to form the wick and bury it into the medium of the pot about one-third� If using a grow tray of medium, locate the wicks below the plant sites and drill through the grow tray at those positions� Make the wicks long enough to reach within ½″ of the bottom of the solution reservoir� Add raw water to the nutrient reservoir, place the lid on top, and add the pots� Seed the pots in place in the system and water the pots from above to initially moisten the substrate� Use a halfstrength nutrient formulation after the plants have their first true leaves unfolding� About 10-14 days later, make up the full-strength formulation solution�
This culture is most suited to low-profile leafy crops such as lettuce, spinach, basil, arugula, and various herbs� The design is similar to the small-scale unit, with the exception that beds (sometimes called raceways) are larger� Cut the boards from 4 ft × 8 ft × 1″ thick “Roofmate” Styrofoam� The raceway can be constructed of 2″ × 10″ treated and painted cedar planks and lined with a 20-mil vinyl swimming pool liner (Figure 13�2)� The raceway may be constructed on the floor or as a raised bed� The raised bed form is better as it can drain by gravity to an underlying cistern (Figure 13�3)�
1� Lumber of 2″ × 10″ dimension� Length to suit your specific needs, but the raceway must be a multiple of 2 ft in length to fit the boards�
2� Swimming pool vinyl liner of 20-mil thickness� 3� Vinyl cement� 4� Various PVC pipes (¾″ schedule 40) and fittings�
5� Lathes 1″ × ¼″ thick or 1½″ × 1½″ aluminum angle� 6� An air pump and air stones are available from fish aquarium stores or aqua-
culture suppliers� 7� Submersible pump with a timer� 8� Nursery landscape weed mat if this is outside or in a greenhouse� 9� 6-8″ nursery staples to secure the weed mat� 10� 50-100-gal cistern tank� The size depends upon the length of the raceway�
For a short raceway up to 20 ft, a 50-gal cistern is adequate� 11� Galvanized or chrome plated ¾″ square steel tubing for a support frame� 12� White oil-based paint�
If the system is located inside the house, a weed mat is unnecessary� The raceway sits above a solution tank so it must be raised up on a supporting frame (Figure 13�3)� Construct the raceway before the support frame�
Make the inside dimensions of the raceway frame ½″ wider and 1″ longer than the total dimensions of the boards� For example, to construct a raceway 12 ft long by 2 ft wide, make the inside dimensions 12 ft 1″ (145″) long by 2 ft ½″ (24½″) wide to allow for some free play and the thickness of the vinyl liner� If the raceway is to be located on a frame, make a bottom of ¾″ plywood� Attach the frame and bottom with stainless steel screws to avoid any corrosion and glue all joints for added strength as water is very heavy� Cut a 1½″ diameter hole at the bottom of one end of the raceway, about 4″ from the end in the center� Paint the inside and outside of the raceway framework with an oil-based paint�
Line the raceway with 20-mil vinyl liner� Place it tightly against the bottom and all corners to get a smooth flat surface� At the corners fold it similar to wrapping a parcel and glue the wrapped corners� Bring the vinyl over the edge of the wooden frame and secure it under a lathe on top around the perimeter with aluminum nails or stainless steel screws� Alternatively, staple the vinyl to the top edge of the frame and cover the staples with ducting tape bringing the tape over the edge to make a very
nice finish as shown in Figure 13�2� To make a very nice finish, screw an aluminum angle on top of the vinyl around the top edge of the raceway� You will have to make a small slit at the top of each corner to permit the vinyl to lay flat at that point� Cut the excess vinyl flush to the wooden frame� Where the drain hole was cut, hold the vinyl tightly and make a cross cut in the vinyl to within ¼″ of the width of the hole� Install a bulk-head fitting through the vinyl and hole gluing the vinyl between the bulk-head fitting seals� Caulk with silicone rubber� The bulk-head fitting must give a complete seal to avoid any leakage of water between the liner and plywood bottom of the frame�
Construct a steel tubing frame to support the raceway (Figure 13�3)� The frame must keep the raceway about 30″ above the floor to permit the cistern to fit underneath� Locate the cistern under the drain pipe of the raceway� The support frame must be level in all directions to get good drainage from the raceway� Locate an air pump at one corner of the raceway frame and run a poly hose down the center connecting to a 6″ air stone�
Place a 1½″ diameter by 9″ long PVC pipe in the drain to maintain 8″ of solution in the raceway� Do not glue this pipe� This is the overflow pipe to re-circulate the nutrient solution to the cistern�
Cut a notch in the top of this pipe so that flow from the raceway will not be impeded by the boards floating on top of the solution�
Install a submersible pump with a ¾″ outlet and plumb it with fittings and ¾″ PVC schedule 40 pipe from the pump underneath and attached to the metal support frame going to the opposite end from the drain� Then, with elbows, extend the pipe over the end of the raceway to enter the top of the raceway as an inlet for the solution (Figure 13�3)� Put a ball valve at the vertical side to regulate the flow� This keeps a constant flow of solution aerating and replenishing the solution in the raceway for the plants�
The next step is to make the boards� Cut the boards 6″ × 2 ft, 1 × 2 ft, 2 × 4 ft, or 4 × 4 ft long exactly depending upon the raceway width� Use a very sharp kitchen knife or gyproc knife guiding it with a straight edge� Alternatively, a saw with fine teeth will do the job� Smooth the edges with fine sand paper� Drill ¾″ diameter holes at 6″ centers for lettuce, arugula, and basil with 4″ centers for small herbs� For 6″ centers start the holes 3″ from the edge� For 1 × 4 ft boards make two rows of four holes forming eight plant sites per board� The hole pattern across the raceway is 3″–6″–6″–6″–3″ (four holes) and the other way 3″–6″–3″ (two rows)� For 4″ centers, start 2″ from the edge and space 4″ apart to get a total of six holes within the row and in the other direction start again 2″ in from the edge to form three rows� They are not staggered in their position� After making the holes, smooth the edges with sand paper� Refer to the diagrams of Figure 13�4 for the board dimensions and hole patterns�
In this design we can eliminate the nutrient reservoir below the raceway� You can even eliminate the supporting frame if you wish to construct the raceway on the floor� Simply set the raceway on top of 1-2″-thick Styrofoam for insulation from a cold basement floor�
Construct the raceway itself of dimensions either 2 or 4 ft wide by whatever length is convenient for your space� Since plywood sheets come as 4 ft wide, make the overall outside bed dimension a maximum of 4 ft� With the framing of 2″ lumber, which is dressed dimension to 15 8″ thick, the sides will use 2 × 15 8″ = 3¼″� The Styrofoam sheets will have to be cut to a width of 48″–(3¼″ + ½″ of play) = 44¼″ or about 44″ to allow sufficient free play between the sides and liner� The boards may be 2 ft or 4 ft × 44″�
Place the raceway at the floor level on Styrofoam insulation or make a frame as described earlier� However, no drain hole for returning the solution to a reservoir tank is needed� Make up the nutrient solution directly in the raceway and keep it mixed and aerated using an air pump and tubing to air stones as explained earlier� This design eliminates the complexity of returning the solution to a nutrient tank, thus avoiding the drainage and irrigation systems requiring a pump, and so on�
Check the pH and electrical conductivity of the solution at least once a day and add a small portion of solution (up to about 10% of the original makeup) every few weeks, if necessary� Change the nutrient solution once every few months by pumping it out with a sump pump and cleaning the raceway with a 10% bleach solution�
The plants that were growing in the raceway can be taken out in situ with the boards and kept moist by stacking the boards together root-to-root� You may also mist the roots with water to keep them from drying while cleaning the raceway� As soon as you finish cleaning the raceway and start filling it with water, place the boards with their plants still in place back into the raceway and then make up the nutrient solution�
This is the most common method of hydroponics for low-profile crops such as, lettuce, basil, arugula, bok choy, and spinach� The growing channels may be constructed from 2″ PVC pipes as shown in Figures 12�9 and 12�10 or it is best to purchase special NFT channels from a hydroponic store� The commercial NFT channels have either ridges on the inside bottom of the channels or a sloped bottom with or without ridges to direct water from flowing around plant roots when the seedlings are transplanted (Figure 13�5)� There are two types of channels: a one-piece fixed top and a two-piece with a removable top to facilitate cleaning between crops (Figures 13�5 and 13�6)� The covers have plant site holes of correct diameter and spacing for the crop you wish to grow�
The NFT system, regardless of whether it is PVC pipe or other channels, must be located on a frame above a solution reservoir� The bench must have a 3% slope back toward the reservoir� The channels must not exceed 12 ft in length to prevent a temperature rise and oxygen loss in the nutrient solution as it travels along the channel� The benching should be at waist height, about 30″�
Many small NFT systems of various sizes and number of channels are available from hydroponic stores and online (refer to the Appendix)� The following materials list is for a system of four channels�
1� NFT channels 12 ft in length or 2″ PVC pipe 12 ft (8 ft length shown in Figures 13�7 through 13�9)�
2� PVC fittings-elbows, tees, reduced bushings, ball valves, and so on� 3� PVC cleaner and glue� 4� PVC piping-1″ and ¾″ diameter schedule 40� 5� A submersible pump with 1″ or ¾″ outlet� Flow rate must be 2 L per minute
per channel� For four channels, a pump of at least 3-4 gal per min (gpm) is needed
with a head (lift) of 6 ft� 6� Drip irrigation tubing-about 10 ft� 7� Square steel tubing ¾″ by ¾″ or lumber 2″ × 2″ treated and/or painted white�
8� A plastic 50-gal nutrient reservoir, preferably opaque in color with a cover� The nutrient tank may be smaller for shorter and less channels per system� For example, two 10-to 12-ft channels can be served with a 20-gal reservoir�
A small system is discussed first followed by further details of larger, more complex systems� Starting with two 8-ft channels and a 20-gal reservoir, the channels can drain at the lower end directly into the nutrient reservoir at the lower end� The first step is to construct the supports for the growing channels� With two channels that are spaced 6-8″ apart, set the drain ends on the edge of the nutrient reservoir (Figure 13�7)�
The support frame can be constructed the same for either 2″ PVC channels or purchased NFT channels� Construct one A-frame “sawhorse” structure 3″ higher than the height of the nutrient tank, for the upper inlet end of the channels� It should be about 2 ft long� If you prefer not to rest the lower end on the nutrient tank, make a second A-frame that is several inches higher than the nutrient tank and make the inlet support frame 3″ higher than the lower one� These support frames can be constructed of wooden 2″ × 4″ lumber and painted white� They can also be made of ¾″ square steel tubing or PVC pipe� But, when using PVC make the frame somewhat different from wood or steel tubing� Use 1″ PVC schedule 40 pipe� First, make a rectangular base 18″ × 24″� In the middle of the 18″ sides attach a tee� From there glue a riser of 14-18½″ depending on the height of the nutrient tank as the taller support must be 5″ above the tank height if the lower support at the tank end is 2″ above the tank� This gives a slope of 3″ for the growing channels� Use 1″ tees at the top of the riser and connect a horizontal pipe between the two tees� This completes the supports as shown in Figures 13�7 and 13�8� Another one exactly the same for the middle
is needed to prevent the channels from sagging with the weight of the solution and plants� Make this one 1½″ shorter than the highest one at the inlet end�
The piping from a submersible pump in the nutrient tank to the upper inlet end of the channels is as follows� Attach a ¾″ pipe to the pump with a threaded male adapter� Make this riser long enough to reach up through the tank lid and to the top of the support frame� Just above the tank cover, install a return bypass line with a ball valve to regulate the flow of solution to the inlets of the channels� In this way, if the pump has more capacity than needed, the flow is shunted back to the tank� From there use a 90° elbow to attach the pipe going on top of the support frames to the inlet end of the channels� At the inlet end attach a tee and make a header going each way�
Glue a cap on one end of the header and a threaded female adapter to which a plug can be placed to permit cleaning of the pipe� This header should be about 18-20″ long to span between both growing channels� From it use a special grommet seal and insert several drip lines for each channel� Two drip lines enter the top of each
growing channel by drilling snug holes� Alternatively convert to ½″ black poly tubing with barbed adapters at the tee and punch holes for drip lines at the grow pipe positions� The solution flows constantly so a timer is not needed for the submersible pump� Refer to Figures 13�7 and 13�8 for details of the design�
If you wish to make the grow channels from 2″ PVC pipes, you must drill the plant site holes similar to that mentioned in Chapter 12 for simple units� Make the holes 2″ in diameter as the mesh pots have a 1 16″ lip around their tops as shown in Figure 12�9� This will prevent the mesh pot from falling into the pipe� Locate the holes in a straight line at 6″ centers for lettuce, arugula, bok choy, and basil� To hold the growing pipe in position on the support frame, use plastic electrical straps around the 2″ PVC growing channels securing them to the 1″ PVC support frame� Glue a 2″ female adapter on the ends of the growing channels and fit them with a threaded plug to enable access for cleaning� A multi-pipe NFT system is set similar to the two-pipe system with the exception of plumbing the drain ends of the grow pipes into a 3″ diameter catchment pipe that returns the solution to the nutrient tank (Figure 13�9)� The irrigation system is the same as described earlier as appears in Figures 13�7 and 13�8�
The next are steps to build a somewhat larger and more complex system� The materials list is basically the same, but with more channels and a larger benching frame� The following is a design similar to that available from American Hydroponics (see Appendix)� The system has eight production channels and two seedling channels to grow 144 lettuce, basil, arugula, or bok choy� It occupies an area of 6 ft × 12 ft� Construct the bench framework first using ¾″ square steel as shown in Figure 13�10� The bench is 34-38″ high� This gives a slope of 4″ in 138″ or about 3%� Since the channels are exactly 12 ft long, make the bench slightly shorter at 11½ ft (138″) to allow the channels to extend out from the bench� There are a total of four cross members placed at 46″ centers� Set these on a base extending the 11½ ft on each side� Put braces between each corner at the top of each cross member as shown in the diagram� It would be best to weld the entire structure, but if that is not possible, drill holes and secure each member with bolts�
Each of the eight growing channels has 1¾″ diameter holes spaced at 8″ centers to permit 18 plant sites per channel as shown in Figure 13�11� The two nursery channels have the same size of holes spaced at 2″ centers to fit 72 seedlings per channel� The production gullies house 144 plants (8 × 18 = 144)� The gullies come with a cover and are ready to set up with the irrigation system� They drain into a closed collection pipe that conducts the solution back to the nutrient tank�
There are many sizes and types of NFT systems available from hydroponic stores and online� If you do not want the work of constructing one, I recommend purchasing a complete unit (see Appendix)� You may also buy NFT gutters of various lengths (4 ft, 6 ft, or 8 ft)�
To grow vine crops use wider channels or larger PVC pipes of 4-6″ diameter� Wider NFT channels of 4″, 6″, and 9″ with plant site holes at 8″ for the 4″ and 6″ wide channels and at 12″ for the 9″ channel are available� Plant hole diameters are
offered for 2″, 4″, and 6″ net pots� The larger net pots can be filled with substrates as expanded clay particles or granular rockwool�
For vine crops use 9″ wide channels with 12″ spacing for 6″ net pots with a substrate� Whatever substrate or sizes of pots are utilized, begin the seedlings in the conventional method of rockwool cubes and transplant to the net pots� When using a substrate in large net pots, this is really a combination of NFT and another culture�
The following is a smaller NFT system using four channels of 8 ft in length� Purchase the channels with end caps and covers from a hydroponic supplier or make your own from 2″ PVC pipes as described earlier� A support frame and inlet and return piping will have to be constructed� The system described is for lettuce, arugula, basil, bok choy, and herbs in 2″ pipes and vine crops in 4″ diameter pipes�
1� Two 8 ft 2″ PVC pipes and two 8 ft 4″ PVC pipes� 2� Fittings: two 2″ caps, two 4″ caps� 3� Construct the support frame of 1½″ PVC pipe or of ¾″ square steel tubing� 4� Return pipe of 3″ PVC pipe schedule 40�
5� Five 3″ tees, two 3″ female adapters, two 3″ thread plugs, two 3″ × 2″ reduced bushings, two 4″ × 3″ reduced bushings�
6� Twenty feet of ¾″ diameter PVC for inlet main and header with fittings for attachment to the pump including bypass and ball valve�
7� Submersible pump of ¾″ outlet of at least 4 gpm capacity� 8� Timer 24-h cycle with 1 min intervals� 9� A 20-gal plastic storage bin with a lid for the solution reservoir� 10� Twenty feet of drip line, with grommets to attach to the inlet header�
Start with the support frame� Construct it of 1½″ PVC pipe or ¾″ steel tubing� Make the frame dimensions 90″ by 54″ wide by 24″ high on the inlet end side and 21″ at the drain end as shown in the diagram (Figure 13�12)� The channels sit on the 48″ wide side� Using a male adapter and several 90° elbows connect the ¾″ inlet line from the pump to a header� Secure the header with strapping underneath the support frame� Install a bypass pipe with a valve above the lid of the reservoir to permit regulation of flow to the inlet pipe� Install the drip lines in the header and into the channels (two per channel)� Alternatively, convert to ½″ poly hose for the header into which the drip lines are inserted� They can be inserted without emitters to achieve a minimum flow rate of 1-2 L per minute (¼–½ gal/min)�
At the drain ends of the channels assemble a 3″ PVC collection pipe that returns the solution to the reservoir� This is held up by the bench frame with brackets� Two methods for the collection pipe and drainage of the channels are feasible� One is to leave the ends of the growing pipes open and allow them to empty into the collection pipe at open slits 2″ wide� If you use NFT commercial channels attach a 1″ diameter drain pipe to the bottom of the gullies at their drain end and drill 1½″ holes in the collection pipe at the positions of the drain pipes from the gullies� The difficulty doing it this way is to seal the joints with glue or silicone rubber to the NFT gully� However, the advantage is that light can be excluded from entering the collection pipe, which will prevent algae growth� If using PVC pipe channels, glue them into the 3″ PVC header using tees� With this method end the collection pipe with threaded plugs to enable cleaning� Then, place one tee in this collection manifold above the tank to conduct the solution to the tank as shown in Figure 13�12� If the former method of an open gully end into the collection pipe is used, cover the outlet ends with black polyethylene to exclude light from entering� Tie a nylon mesh screen over the end of the return line to collect any debris returning from the growing channels� Drill holes in the reservoir lid for the entrance of the return pipe and for the inlet line and bypass line� You may also install a 100 mesh filter in the inlet line above the pump before the bypass to collect any extraneous particulate matter�
Remember to make or purchase gullies with the correct size and spacing of plant site holes for the specific crops you wish to grow, either low-profile or vine crops� If you want to grow vine crops, you would need only two NFT channels, spaced about 2 ft apart� Then V-cordon training the plants to an overhead support wire or hook
using plastic string and vine clamps as is explained later in Chapter 24 on the training of vegetable crops�
For growing both vine crops and low-profile plants such as lettuce, herbs, and arugula, space the 2″ diameter pipes for the low-profile plants at 7″ centers and then the next two 4″ pipes at 20″ centers� It would be better to use large net pots with some expanded clay substrate for the vine crops to increase root aeration than simply setting the plants in their growing cubes into the bottom of the channels�
In this system arrange the NFT channels mounted with brackets to fences, walls, garages, or any vertical surface having good light (Figure 13�13)� Use the standard 4″ wide gullies� The most appropriate crops include lettuce, arugula, basil, strawberries, and herbs� The system consists of two or three gullies of length up to 12 ft, the choice depending upon the available space� A 30-gallon solution reservoir with a lid collects and recycles the solution through an inlet header and return plumbing�
1� NFT channels 8-12 ft long� 2� Wall bracket support system� These are available in hardware and building
supply stores� These should be heavy duty forms that screw into the wall� Most have adjustable shelf positions�
3� A 30-gal plastic solution tank with cover� 4� PVC piping to fit the channel drain outlets� 5� Submersible pump, fittings, ball valve, and ¾″ PVC or ½″ black poly inlet
hose�
Attach the wall support bracket with 2″ screws to the structure holding the NFT garden� At least two of the vertical bracket plates are required for 6-8 ft NFT gullies and three to four for anything longer� Position the support brackets into the backing plates so that at least a 3% slope is obtained� In this system, the solution will run from one gully into the next one and finally into the nutrient reservoir at the bottom� As shown in the diagram (Figure 13�14), slope one gully in one direction and then the next one in the opposite direction working down so that the solution flows from the lower end of the channel above to the higher (inlet) of the next one below� It is easiest to use flexible hose, like black poly hose, from the drain outlet pipe of the channel above to enter the top of the inlet end of the next channel� The lowest gully has a drain hose into the nutrient tank� Refer to the diagram of Figure 13�14 for details�
The pump lifts the solution through a ½″ diameter black poly hose from the reservoir to the inlet end of the highest grow channel� Do not use more than two to three channels hooked together or the solution temperature may rise and oxygen deficit may occur to the plant roots� Connecting three 12-ft gutters together in one section is an NFT solution flow through 36 ft� That is very long for growing under high light intensity summer weather� It would be better to use two sections with two channels each for a total of four, providing the height of the wall is sufficient� Each channel must be a minimum of 16″ apart to give adequate light to the one immediately below�
If constructing two separate sections of NFT, use the same inlet header, but install a ball valve before the inlet hose enters the upper gully� This will balance the flow to the two sections� Collect the drainage from the second channel (lower one) and direct the return pipe from each section back to the nutrient tank as shown in Figure 13�14� In effect there are two separate systems but one common inlet header with two individually regulated outlets�
This design again is suited only to low-profile plants� The concept is the same as that for the wall garden NFT systems, but instead of attaching the growing channels to a vertical surface, they are supported on an A-frame� The length of the A-frame should be 11½ ft to support 12-ft long channels� The size of the A-frame can be varied to fit any length of NFT gullies� I recommend a minimum of 8-10 ft to justify the amount of work needed in constructing the A-frame� Make the framing 6″ shorter than the gullies to enable placement of inlet and return pipes�
Construct the A-frame in the form of an isosceles triangle having two equal sides (Figure 13�15)� Locate the first channel 16″ above the floor level so there is enough height to enter the reservoir� Other channels have 10″ between them to reduce any mutual shading by mature plants�
This spacing is sufficient for six channels on each side to give a total of 12 channels on the A-frame as shown in Figures 13�15 and 13�16� The slope of the sides of the A-frame should be shallow enough to permit adjacent channels from overlapping in their horizontal space� Each channel ideally should be offset 4″ horizontally from the adjacent ones next to it� With the sides 75½″ and the base 48″ each channel has a space of 48″/12 = 4″� The altitude of the A-frame is 6 ft� A horizontal bench would contain eight channels in a 4 ft width� The result is an additional four channels or 50% increase in the number of plants� A 12 ft × 4 ft A-frame with 12 gullies has a total of 12 × 18 plants/gully = 216 plant sites�
1� The A-frame is to be constructed of ¾″ square or 1″ diameter round galvanized steel tubing� Calculate the length according to the dimensions� The frame members may be welded or bolted� The A-frame may be covered with ¼″ thick white plastic sheeting or a Mylar reflective cover to get more efficient use of light� However, that is not essential�
2� The reservoir should be 100 gallons for a 12 ft long system or 50-60 gallons for a 6-8 ft long system� Due to the cost and labor in building the A-frame, I recommend to plan on a 12 ft system�
3� A submersible pump with a ¾″ outlet, minimum volume of 10 gpm with a head of 15 ft�
4� One filter of 100 mesh by ¾″ diameter� 5� Inlet piping fittings of ¾″ diameter include male adapters, ball valves, tees,
90° elbows, and ½″ barbed adaptors for ½″ black poly hose and figure “8” caps�
6� Other fittings include drip lines (two per gully), about 30 ft, 24 compensating emitters of 1 gph, and twelve 90° elbows (1″) for drain spouts from the end of the channels to the collection pipe�
7� Twelve 12-ft NFT gullies with covers, end caps, and drain spout� These have holes spaced at 8″ centers� It is best to use channels that have separate covers that can be removed for cleaning�
8� One collection pipe of 2″ diameter-about 10 ft� 9� Collection/return pipe fittings (2″) including caps, 90° elbows, and tees
or cross fits with 1″ × 2″ reduced bushings� Follow the diagram plan of Figure 13�16�
10� Support brackets to hold the NFT channels on the A-frame� Use four per channel, so that is a total of 48 brackets� These are bolted to the A-frame bars� Make the brackets from 1″ wide by 1 8″ thick steel� Form their shape to fit the bottom of the NFT gullies similar as shown in the diagram�
Construct the A-frame first and later mount the NFT channels onto it after covering the A-frame with sheets of plastic or Mylar, if it is being used� Locate the solution reservoir at the drain end of the A-frame� Install the pump with fittings, a union above the lid of the reservoir and then the bypass and filter� Then, with a tee, make a header to each side of the A-frame under the first NFT gully and then up to the inlet location using a ¾″ × ½″ slip-thread female adapter where the ½″ poly adapter is attached to convert to the ½″ black poly hose� This will be at the base of the first NFT channel on each side� Punch the holes for the emitters; install them and the drip lines to the top of the channels (two per channel)�
Mount the 2″ collection pipe header in the middle of the A-frame at the drain ends of the NFT gullies� Use several 90° elbows with a short 4″ piece of pipe at the lower end of the collection pipes to enable making a bend from the angle of the A-frame to the horizontal section joining the two collection pipes just above the nutrient reservoir as shown in Figure 13�16� Use a 90° elbow to enter the nutrient tank� You may put a short spout at the end of the elbow, but do not glue it so that you can remove it when accessing the reservoir for cleaning� Place a cap on the top end of the 2″ collection pipe, but do not glue it in case access to clean the pipe is necessary� Attach the 1″ drain pipes from all of the NFT gutters to the 2″ collection pipe header with tees or a cross fitting� Use only silicone to seal the entrance of this spout into the collection pipe as at times the gullies may have to be removed� Just a note here that when cleaning the gullies after a crop, use a piece of towel soaked in a 10% Clorox solution and scrub the channels� If you have other plants still in the other channels, plug the drain line in the gully with another towel before using the bleach solution to prevent the bleach solution from going back to the nutrient tank� After cleaning, dry the gully with a towel and let the channels air dry before placing in your seedlings�
Drill holes in the nutrient reservoir lid to accommodate the pipe from the pump, the bypass line, and the return drain line�
If you want to place a covering over the A-frame do that now before securing the support brackets for the NFT channels� Remember to locate the support brackets to give a 3% slope to the gullies from the inlet end to the outlet end, that is, about 4″ of slope� The support brackets must be screwed, using self-drilling metal screws or bolts, into the vertical members of the A-frame� Secure the brackets at the inlet and outlet ends first, then attach those on the other frames to get their position accurately�
Position the NFT channels, make the inlet and drain connections, and put water in the reservoir to test the piping joints� Balance the ball valve at the bypass to get the correct flow into the gullies�
This is the most complex and difficult system to build, so do not be discouraged� There are many other more simple and equally productive hydroponic systems to construct as alternatives to the A-frame NFT system�
In a larger hobby ebb and flow hydroponic system use a series of trays sitting on a framework above a nutrient reservoir� This is a recycle system where the solution floods the substrate from below and then drains back to the reservoir awaiting the next irrigation cycle� A time clock or controller activates the pump several times a day to flood the growing beds� The frequency of irrigation cycles, as mentioned in the previous chapter, is dependent upon the crop, stage of plant growth, and substrate water retention�
The ebb and flow method is suitable to most crops including low-profile and vine crops� Since the substrate of choice must have good porosity, use some form of aggregate� In this case, we could also call it gravel culture� Use expanded clay, ¾″ crushed igneous rock, or ¼″ pea gravel�
In this system beds are constructed 2 ft wide by any length up to 20 ft by 10″ deep� Construct one or two beds with a 3 ft aisle between them for access� Make the beds in the same way as was done earlier for the raft culture raceway of the narrower 2 ft width as shown in Figures 13�2 and 13�3� Build the sides of the bed with 2″ × 10″ treated and/or painted cedar lumber� The bottom is ¾″ plywood� All lumber joints are screwed and glued� The beds are lined with a 20-mil vinyl as for the raceways using the same methods� Each bed must be supported on a wooden or steel framework�
1� Lumber of 2″ × 10″ dimension for all sides and ¾″ plywood for the bottom of the bed� Since plywood comes in 4 ft × 8 ft sheets, make the width of the bed(s) 2 ft outside dimensions to achieve optimum use of the plywood�
2� Swimming pool 20-mil thick vinyl� 3� Vinyl cement� 4� PVC pipe and fittings� 5� Lathes 1″ × ¼″ thick� 6� Submersible pump with a timer� 7� White oil-based paint and primer� 8� Nutrient reservoir� The volume depends upon the total volume of void
spaces in the substrate of the bed(s)� Calculate the total volume of the bed and multiply it by the percent of
void spaces in the rock substrate� Typical crushed ¾″ rock has a void space of about 38%� Pea gravel would be less, closer to 25%� The finer the material the less void space is present� If you wish to test your substrate for its void space, place a given volume of gravel in a container such as a 5-gal bucket and add water to it until the water level just reaches the surface� Pour off the water into another bucket and measure this volume of water with a graduated cylinder� The fraction of that volume of water over the volume of the gravel gives you the percent of void spaces� To allow for some loss of water by the plants make the nutrient reservoir large enough to contain at least twice the void space of the substrate�
9� Metal frame to support the aggregate ebb and flow beds� This should be constructed of 1″ square tubing as the weight will be substantial, especially during an irrigation cycle when the bed is full of solution�
10� Use light weight expanded clay aggregate (LECA)�
Volume Calculation Here is an example to calculate the volume on aggregate needed: Volume = length × width × height (V = LWH)� For a 10 ft long bed by 2 ft wide by 9″ deep: V = 10 ft × 2 ft × 9 12 ft = 15 cubic ft� One cubic yard is equal to 27 cubic ft, therefore the number of cubic yards is: 15 27 = 0�56� This is slightly over one-half a cubic yard� Order one cubic yard and there will extra for use later�
Weight Calculation The LECA weighs 1200-1300 lbs/cu yd, whereas, ¾″ crushed gravel weighs about 2800 lbs/cu yd� The total weight for a 10 ft × 2 ft bed of LECA aggregate is therefore: 0�56 × 1200 lb = 670 lbs� Obviously, you need to make the bed and the supporting frame strong enough to withstand this weight�
Solution Volume Calculation (Using a 10 ft Bed with Expanded Clay) V = 15 cu ft × 35% void space = 5�25 cu ft� Multiply by two for evaporation loss by plants: 5�25 × 2 = 10�5 cu ft� Convert to gallons: 1 cu ft = 7�48 U�S� gal; therefore: 10�5 × 7�48 = 78�5 gal� In this case, use a 100-gal nutrient reservoir to give adequate solution�
First construct the bed(s) using 2″ × 10″ lumber for the sides and ¾″ plywood for the bottom� Be sure to use screws and glue in the joints� Install the vinyl liner as described earlier for the raft system raceway, but the plumbing will differ� Install a 1½″ diameter inlet pipe in the center of the bed in the middle lengthwise using bulkhead fittings to seal the pipe with the vinyl liner as discussed earlier for the raceway� An overflow pipe of the same size diameter and 8″ high is placed in the bed with similar bulk-head fittings within 12″ of the end of the bed nearest the nutrient reservoir� This maintains the solution level in the bed during an irrigation cycle�
Make the support frame next before the irrigation system from the pump and the drain line back to the reservoir� Using galvanized or chrome steel square tubing is preferred over wood for the bed framework� Be sure to make a separate frame for each bed� The top of the framework should be 30″ high to give sufficient height above the nutrient tank� The width should be about 1″ wider than that of the bed� Due to the weight of the aggregate and solution make cross supports every 3-4 ft� Tie the entire framework together at the base and top with bars both across and lengthwise as shown in Figure 13�3� At the edges of the top cross bars where the bed sits, extend the vertical tubes 1″ above to act as a guide to contain the bed�
After placing the bed on top of the framework start the plumbing� A submersible pump with a 1½″ outlet and capacity to fill the bed within 5 min will ensure rapid fill and drain of the bed� The volume of the void spaces in the bed in our example of a
10 ft long bed was 5�25 cubic ft or about 40 gal� The pump must be capable of filling the bed with 40 gal within 5 min so the pump outlet volume should be at least 8 gpm (40 gal/5 min)� Assemble the piping from the pump in the following sequence: male adapter and bushing to 1½″ diameter pipe; 1½″ union; a bypass pipe with a 1½″ × 1″ tee (or 1½″ tee plus a 1½″ × 1″ reduced bushing); 1″ ball valve on a 1″ bypass line; 90° elbows to take the 1½″ inlet line from above the solution reservoir underneath the supporting framework for the bed and then entering the center of the bed� Within 2″ of the inlet to the bed install a 1½″ union so that the line can be dismantled if necessary� The return overflow line should be 1½″ diameter from one end of the bed closest to the nutrient reservoir� This also can be fastened to the underside of the bed framework� Drill holes in the cover of the nutrient tank for the bypass, main inlet, and return pipes� The piping differs somewhat from the raceway of Figures 13�3 and 13�4 in that an air pump is not needed and the ¾″ inlet line is replaced with the 1½″ main to the bed�
Fill the bed with the expanded clay aggregate to within ½″ of the top� Place a screen over the inlet and overflow pipes before filling with the aggregate� One day before transplanting, sterilize the aggregate with a Zerotol solution (hydrogen dioxide) of 1:100 concentration� This is equivalent to 1¼ fluid ounces per gallon� Water the medium with the Zerotol solution using a watering can from above� Alternatively, put 1 gal of Zerotol in the 100-gal solution tank and pump the solution into the bed several times keeping the pump on for half an hour each time to allow the solution to circulate through the substrate and overflow back to the reservoir� This process will kill most fungi�
There is one commercial ebb and flow system that uses a series of 5-gal pots, instead of beds, filled with lightweight aggregate� This system is described in detail with drawings (Figures 20�3 and 20�4) in Chapter 20� There is a 6-pot and a 12-pot system� The key components to the system are a 55-gal drum nutrient reservoir; a 5-gal controller bucket; 6 or 12 growing pots with felt liners to prevent debris entering the drain lines; two submersible pumps, fittings, and tubing; two timers; and a float valve�
A 400-gph pump is positioned in the solution reservoir that circulates solution to the controller bucket upon an irrigation cycle governed by one timer� The solution flows from the controller bucket by gravity to each of the grow buckets until they all reach a set fill level that is equivalent in all of the buckets and control bucket� A float valve in the control bucket then stops additional inflow of solution to the control bucket� When the timer for the main pump stops the irrigation cycle to the controller bucket, the second timer activates a smaller submersible pump of 160 gph in the control bucket to start pumping the solution back to the main reservoir� The two timers must be synchronized so that when one starts the other must be off� The solution from the grow pots drains back to the control bucket as the level in the control bucket is lowered by the pump sending the solution back up to the main 55-gal nutrient drum�
One timer is designated the “fill” timer and operates about 20 min during an irrigation cycle� The irrigation cycles are usually ever few hours according to the plant stage of growth and nature of the crop� The other timer called the “drain” timer activates the control bucket pump for about 40 min during a drain cycle as it takes more time for the solution to drain back from the grow buckets than it does to fill them�
This ebb and flow commercial hydroponic system costs about $450� For more information visit the website of “HTG Supply” listed in the Appendix�
You could construct this system yourself� The most challenging aspects would be to locate all of the various fittings needed to connect the distribution hoses, drain screens, and so on to the grow buckets� Each of the pots must be connected to the control bucket with special fittings (grommets) that will seal them to the buckets without leakage� Most are ½″ and ¾″ diameter poly hose fittings�
Drip irrigation is central to all other hydroponic cultures with the exception of aeroponics� It is used with sand, perlite, vermiculite, small expanded clay, sawdust, rockwool, peatlite mixes, coco coir, rice hulls, and any combination of these as a mixture� Irrigation by a drip system is the common method of providing nutrient solution to the base of plants in all of these hydroponic cultures� Sand and sawdust cultures are contained in beds, whereas peatlite mixes, small expanded clay, and rice hull mixes are better in pots� Rockwool and coco coir cultures use plastic “slab” sleeves� Perlite may use slabs or special pots such as “bato buckets�” All use drip irrigation� In the following example, re-cycled systems are used for one bench with bato buckets and the other with high-density rockwool slabs� The larger high-density slabs will support six tomato plants each providing they are V-cordon trained as explained in Chapter 24�
The following components make up a drip irrigation system� The materials listed are for an indoor drip system irrigating two 10-ft rows of pots with two plants each or 8″ wide slabs with six plants each� If these are vine crops, each plant requires 4 sq ft of floor space� Therefore, a growing room of dimensions 12 ft long by 12 ft wide has a total area of 144 sq ft� The maximum number of vine crops in that area is 144/4 = 36 total plants of tomatoes, peppers, or eggplants� European cucumbers must have a minimum of 9 sq ft so the area would contain only 16 plants� You will, however, grow a combination of these crops, for example, 4 cucumbers, 18 tomatoes, 6 peppers, and 4 eggplants� Space the rows 6 ft apart� The first row is 3 ft from the wall and there is 6 ft between it and the next one, making it also 3 ft from the other wall� In our example, (Figure 13�17), the first row with the bato bucket system has 6 peppers, 4 eggplants, and 4 cucumbers and row two in the rockwool slabs has 18 tomato plants�
1� A submersible or centrifugal self-priming pump with timer� 2� A 35-gal tank with cover� 3� Compensating emitters of 0�5 gph� 4� Drip line of 0�160-0�220″ diameter (36 plant drip lines × 18″ = 54 ft)� 5� Barbed stakes: 36 6� Two figure “8” end stops or 3″ × 1″ PVC� 7� Schedule 40, ¾″ PVC pipe: 10 ft 8� Various ¾″ PVC fittings including male adapters, tees, 90° elbows, ball
valves, ¾″ × ½″ slip-thread reduced bushings (2)� 9� 20 ft of ½″ black poly hose with ½″ barbed adapters (2), 1″ hose clamps (2)�
10� PVC glue and cleaner� 11� A poly punch tool to make the holes for the emitters in the poly hose� 12� 100 mesh filter� 13� Lumber or ¾″ steel square tubing for supporting the pots on frames or slabs
in trays� 14� Lumber to construct trays for slabs�
Here only the assembly of the drip irrigation system is discussed as the remaining growing systems explain the various substrates in pots or slabs and any supporting structure� Starting from the pump, attach a ¾″ main inlet line with a male adapter, then above the tank make a bypass line using a tee, ball valve, and 90° elbow� Above the bypass put a 100-mesh filter in the main line then continue with 90° elbows and the line to a header at the front of the plant rows�
Then use two elbows and a reduced slip-thread busing in each to adapt to the ½″ poly adapters� The ½″ black poly hose is attached to each adapter and runs to the end of each row where a figure “8” end stop is placed� Punch holes for the emitters at the location of the plants and insert an emitter in each� Attach a drip line to each emitter at one end and a barbed stake at the other that sits at the base of each plant�
Bato buckets are special pots designed for using coarse substrates such as perlite and expanded clay� I do not recommend them for finer substrates since the buckets retain a small reserve of solution at the bottom of the pot� Also, any recirculation of the leachate with a fine medium would be more complex in managing due to potential salt build-up� The buckets have an indentation at the back to enable them to sit on a 1½″ drain pipe� A ¾″ diameter double elbow forms a siphon to drain from the pot to the drain pipe (Figure 13�18)� This siphon keeps about 1″ of solution in the bottom of the bucket� This persistent reservoir of solution in the bucket is important with coarse substrates�
They are made by a company in Holland and hence are also referred to as “Dutch” bato buckets� These buckets are suitable for vine crops� They are made of rigid plastic, measuring 12″ × 10″ × 9″ deep (Figure 13�18)� The bato buckets are placed on a 1½″ or 2″ PVC drain pipe to enable recirculation of the nutrient solution� The rows are spaced 6 ft apart and the bato buckets are staggered at 14-16″ centers within the rows� Some hobby units are available as a self-contained supporting structure, pots, and irrigation system in compact configuration (Figure 13�19)� As long as the plants are V-cordon trained to optimum spacing at the top of the crop, the narrow spacing of the pots is functional� Two plants are grown in the buckets, with the exception of one for European cucumbers to obtain the correct growing area per plant� Irrigation is by a drip system�
In an indoor bato bucket system, the pots will have to be raised above a solution tank with a framework of steel or wood� The frame has to be just high enough to permit gravity flow of the recycled solution to the tank as shown in the diagram of a commercially available hobby system (Figure 13�20)�
The following materials list is to build a system of two 10-ft rows of bato buckets with the same irrigation system as described previously under “Drip Irrigation
System�” The irrigation system is exactly as outlined; therefore the materials for that portion include all items 1-13 listed earlier with a 50-gal tank� The additional materials needed are listed in the following text:
1� There are nine bato buckets per row, so a total of 18 bato buckets� 2� Thirty feet of PVC pipe of 1½″ diameter for the drain collection lines� 3� Various 1½″ PVC fittings for the drain return to the solution tank include
90° elbows (3), female adapter plus threaded plugs (2), and one tee�
Construct the supporting framework as shown in Figures 13�19 and 13�20� Make two individual benches, one for each row of pots� You may place ½″ thick plywood on
the top of the benches, but it is not necessary for bato buckets as they are supported at their drain end by the drain pipe� Once the framework is completed make up the drip irrigation system as described earlier� Then, secure the drain pipe system on the frame under the drain end of the bato buckets� Cut 1″ diameter holes along the top of the drain pipe at the positions of the pots (14″ centers starting 8″ in for the first one)� Join the two drain pipes with elbows and a tee to a common header that then enters the top of the solution tank� Locate the nutrient tank between the rows at the back wall� Connect all of the inlet pipes, bypass, filter to the pump and make up the header with risers up to the top of the first bato bucket in each row and connect, with an elbow and adapter, the black poly hose with the emitters and drip lines as shown in Figure 13�21�
One day prior to placing the pots with the perlite, moisten the perlite and flush the substrate with Zerotol (1¼ fl oz per gal)� Upon positioning the bato buckets, place the black poly hose along the top of the pots� The pots are now ready to transplant� During transplanting put one drip line with a barbed stake at the base of each plant� Irrigate 4-5 times per day with 5 min duration per cycle� Adjust the frequency of cycles with the stage of plant growth and cycle duration for 20% leachate�
Start seedlings in rockwool cubes that are transplanted to rockwool blocks before a second transplant (about 5-6 weeks after sowing for most vine crops except
cucumbers about 2 weeks) to rockwool slabs� Rockwool properties and products were discussed in Chapter 11�
For consistency in description of materials and components, the same size of rockwool system as for perlite bato buckets is presented that grows 36 vine crops in an area of 12 ft × 12 ft� There are two rows of plants, but instead of bato buckets, use 8″ wide rockwool slabs� The supporting framework for each bed differs somewhat in that it should slope 3% toward the solution tank�
A tray under the rockwool slabs collects the leachate from the rockwool slabs and returns it to the nutrient reservoir� To contain 8″ wide slabs construct watertight trays 10″ wide by 4″ high by 10 ft� Each tray has three slabs each with six plants of tomatoes, peppers, or eggplants as shown in Figure 13�17� Grow only three European cucumbers per slab to meet spacing demands of the plants� V-cordon train the plants as outlined in Chapter 24� To make the return tray waterproof, line it with 20 mil vinyl, folding and gluing it as was shown in the raceway construction in raft culture� A 1½″ diameter drain pipe is installed at the lower end within 2″ of the tray end in the same way as described for the raceway� The drains of the two trays are attached with a union to the collection pipe header going to the solution tank� The irrigation system is the same design as for the bato bucket perlite system shown in Figure 13�21� Items 1 through 13 of the materials for the drip irrigation system with a 50-gal tank are used in addition to the following�
1� Six rockwool slabs 4″ thick by 8″ wide by 39″ long� 2� Fifteen feet of PVC pipe of 1½″ diameter for the drain collection lines� 3� Various 1½″ PVC fittings for the drain return to the solution tank include
90° elbows (5), unions (2), bulk-head fittings (2), and one tee� 4� 1″ Styrofoam to insulate the slabs� 5� ¾″ thick plywood� 6� Fifty feet of 1″ × 4″ lumber for tray sides and ends� 7� Two pieces of 20-mil vinyl swimming pool liner 2 ft wide by 12 ft� 8� Vinyl cement� 9� White oil-based paint�
The benches for the slab trays are constructed the same as for the bato buckets with the exception of the 3% slope to the solution tank� The inner dimensions of the trays are 10″ × 10 ft × 3½″ high� Cut the plywood to 10 ft 4″ long by 11½″ wide� This is the bottom of the tray� Screw and glue the 1″ × 4″ boards around the perimeter of the plywood� Paint the wood after assembly, but before placing the vinyl liner� Drill the drain hole within 2″ of the end of the tray to get a snug fit for the 1½″ diameter pipe and seal it with bulk-head fittings as described in the construction of raceways earlier and as shown in Figure 13�22�
Once the collection trays are completed, put them in place and make up all of the return lines and attach the header to the trays with a union so that they can be dismantled for cleaning and/or repair� Then, fabricate the drip irrigation lines with the inlet pipe, bypass, and so on from the pump�
Test all of the irrigation and drainage systems with raw water in the solution tank to detect any leaks�
A key component is the 1″ thick Styrofoam� Use the high-density “Roofmate” type of Styrofoam� Cut the Styrofoam strips 8″ wide and a total length of 9 ft 8″ long so that they do not cover the drain as shown in Figure 13�22� The Styrofoam strips are placed immediately underneath the slabs� The Styrofoam between the bottom of the return tray and the slabs has two important functions� First, it insulates the slab keeping the roots warm� Second, it raises the slabs up slightly and away from the sides of the tray to permit easy flow of the leachate� After the slabs have been presoaked for several hours, cut drainage slits 1″ long on a 45-degree angle from the base of the slab liner at the level of the Styrofoam underneath� These drainage cuts are positioned between the plants� Three cuts are sufficient� Cut them on the same side (only one side) of each slab�
Seedlings are sown in 1½″ rockwool cubes, transplanted to 3″ blocks, and finally to the slabs after 5-6 weeks from sowing� Remember to presoak the slabs with a half strength nutrient solution prior to transplanting the seedlings in the blocks� At that time make up the nutrient solution in the tank�
Frequency of irrigation cycles is dependent upon stage of plant growth and the crop� Make the duration of any given cycle long enough to get at least 20% leachate�
The entire setup for coco coir culture is the same as for rockwool culture� The slabs for coco coir are the same dimensions as those for rockwool; however, they also make “mini” slabs that are shorter than the normal ones and are good for two plants only�
The only difference between these two cultures is the frequency and duration of irrigation cycles� Coco coir retains much more water than rockwool, so fewer irrigation cycles are needed� Leachate can be reduced to about 15% maximum with a shorter duration of any cycle�
Seedlings may be started in coco coir cubes and blocks such as those sold by Jiffy Products, but most growers still use the rockwool cubes and blocks and transplant to the coco coir slabs by setting them on top of the slabs as is done with rockwool slabs�
This is basically a wick type of system of a series of pots, but a patent system due to a special “AQUAvalve” that regulates the irrigation to the pots� For details visit their website (see Appendix) and Figures 13�23 and 13�24� They recommend using substrate 50/50 mixes such as coco/perlite, coco/expanded clay, and rockwool/ expanded clay�
The AutoPot requires no power, pumps, or timers to operate� It functions on the gravity of solution from a tank� This flow of solution to the pots is regulated by the AQUAvalve through gravity from the solution tank� It fills a tray under two pots to about ¾″ in depth and does not fill it again until the solution is used up by the plants in the pots� Each tray holds two pots� A capillary-like disc is set in the tray under the pots� A black “matrix” disc is set in the bottom of the pots before filling with a substrate� This also acts in bringing the solution in contact uniformly with the substrate�
This culture is not feasible on a larger scale than the small indoor units that were described in Chapter 12� A somewhat larger unit may be constructed as an A-frame� In this system make an A-frame of 1¼″ diameter PVC pipe and secure 1″ thick Styrofoam on the outside to hold the plants� The frame must sit above a nutrient tank� The width of the base should be a few inches narrower than the nutrient reservoir so that the solution will drain back to the reservoir� The system can grow low profile crops and medicinal plants whose roots are harvested for vitamins or drugs�
The following list of materials is for an A-frame of 3 ft wide base and 4 ft long� The height of the sides is 4 ft� The sides are therefore 4 ft × 4 ft with the bottom edge sitting on top of the nutrient reservoir that is 3 ft × 4 ft × 9″ deep� Construct the nutrient reservoir of wood and line it with 20-mil vinyl as was done for the raceway system�
1� Lumber for the reservoir includes 14 ft of 2″ × 10″ and ¾″ thick plywood for the bottom�
2� A piece of 20-mil vinyl liner 6 ft × 8 ft� 3� A-frame materials include: 1¼″ diameter schedule 40 PVC pipe, 90° elbows,
and tees�
4� A high pressure submersible pump with 200-mesh filter� 5� PVC pipe of ¾″ diameter schedule 80 supporting and connecting to the mist
nozzles� 6� Various PVC fittings for the mist distribution pipe� 7� A 24-h timer with minute intervals� 8� Two sheets of 4 ft × 8 ft × 1″ thick Roofmate Styrofoam� 9� Various hardware of bolts, plastic electrical ties, screws, glue, and so on�
Construct the nutrient reservoir with outside dimensions of 4 ft × 3 ft� Be sure to use screws and glue on all joints including the plywood bottom� Fold in the vinyl liner as described for the raceways previously� Paint the reservoir with white oil-based paint before lining it� This reservoir has no drain�
Once the reservoir is completed build the A-frame to fit onto it� Assuming that the exact outside dimensions are 48″ × 36″, make the A-frame slightly smaller to allow for the 1″ Styrofoam that will cover the sides and ends of the A-frame� The inside of the Styrofoam must overlap the reservoir frame by ½″ to permit the moisture when irrigating to run back into it� Refer to the drawings of Figure 13�25 for details� The outside dimensions of the A-frame without the Styrofoam then is as follows: width: 33″ less ½″ on each side = 32″; length: 48″ less ½″ on each end = 47″� First, construct the two ends using 1¼″ PVC pipe as shown in Figure 13�25� The lower base cross member is 36″ long in order to rest on top of the nutrient reservoir sides� One horizontal 1¼″ pipe (47″) going lengthwise is attached by stainless steel screws or bolts in the corners of each “A” to complete the frame�
Fit the two 36″ cross members of 1¼″ diameter PVC with a 90° elbow on each end at exactly the outside width of the nutrient reservoir so that these supports will fit snugly against the outside wall of the reservoir to strengthen it� These are attached to the top sides of the tank using 2″ self-tapping stainless steel screws� Fasten with selftrapping stainless steel screws the peak of the frames together using the horizontal member at the top angle�
Cut the Styrofoam to fit the sides and ends securing them to the A-frame with stainless steel self-tapping screws� Be careful that your measurements are correct so that the insides overlap into the solution reservoir about ½″ to allow drainage back to the solution tank to prevent leakage outside� Refer to the diagrams of Figure 13�25 for details� Cut ¾″ diameter holes in the side Styrofoam boards at 6″ × 6″ for lettuce, arugula, basil, and some herbs or 4″ × 4″ centers for smaller herbs� This is similar to the spacing for boards of raft culture so the 4 ft × 4 ft board would hold 64 plants at 6″ × 6″ spacing� Leave the Styrofoam ends of the A-frame off until the irrigation system is completed�
Make up the irrigation system using ¾″ diameter Schedule 40 PVC from the pump� Install the 200-mesh filter at the front of the header� Place the header with the mist nozzles on top of 1″ PVC frame cross members at 12″ above the nutrient reservoir� Install four mist fogger heads at 12″ centers in line along the top of the pipe� The position of the first mister is 6″ from the end and the other three are at 12″
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centers making the fourth one 6″ from the opposite end� A timer activates the pump to operate the mist cycles� The frequency and duration of the cycles depends upon the crop and its stage of growth, but as a guideline fog every few minutes for 5 sec, day and night�
This is a system developed to increase the number of plants in a unit area occupied� This system is for low-profile plants and is particularly suitable to most herbs and strawberries� Plant towers need about 10-12 sq ft of floor area to allow for adequate light� The best method of construction is with the use of special Styrofoam pots available in the marketplace (see Appendix for suppliers)� While in some cases you can grow bush tomatoes, peppers, or eggplants, light must be sufficient to penetrate the whole crop canopy� With those crops put only half the number of plants in a tower� With the square pots that are available, plant in the corners of the pots� The plant towers must be supported with a central pipe and be secured above by a cable or other bracket to the ceiling� The towers use a drip irrigation system, two drip tubes in the top pot and one in the middle pot of the tower� The towers must sit on top of a collection pots connected to piping that will conduct the solution back to a nutrient reservoir� I do not recommend using polyethylene sacks as they break with age� You can also construct a column from large diameter PVC pipes such as 8″ diameter� But, again the square Styrofoam pots are better to make transplanting or seeding with subsequent plant support easier than will be the case with pipe columns or sacks�
In the previous example for the bato buckets in a 12 × 12 ft growing space, we can fit about 10-12 plant towers� Here is a list of supplies needed for 10 plant towers� Seven pots per tower are sufficient as the pots are 9″ × 9″ × 8″ tall� Seven pots is a height of 56″� In addition to the pots is the height of the collection pot, at least 10″, plus the support frame height of 20″ for a total tower height of 86″� That height will just fit in a normal house ceiling height of 8 ft with some room above for the irrigation system, tower supports, and so on�
The towers are at 24″ centers with the first located 18″ from the wall� There are five plant towers per row and two rows spaced at 3 ft – 6 ft – 3 ft distances starting from the side wall of the room as shown in Figure 13�26� A 2″ diameter PVC collection pipe at the base of the plant towers returns the solution to the nutrient tank�
1� For up to 10 plant towers use a plastic storage bin of 50 gal as a nutrient tank�
2� If the plant towers are seven pots high you need 70 pots for 10 towers� 3� Thirty feet of 2″ PVC schedule 40 pipe for the drainage return pipe� 4� Fifty feet of drip line� 5� Thirty compensating emitters of 1-2 gph� 6� Time-clock controller with 24-h and 60-min increments� 7� One submersible pump having a lift capacity of 10 ft with 30 psi pressure�
8� Twenty feet of ¾″ PVC Schedule 40 pipe as the main to the height of the plant towers�
9� Thirty feet of ½″ black poly tubing� 10� Various PVC fittings including a ¾″ bypass ball valve, four ¾″ male adapt-
ers, six 90° elbows (¾″), two ½″ slip-thread reduced bushing, and two ½″ male barbed adapter to poly tubing�
11� Punch tool for making the holes for the emitters for the black poly lateral tubing�
12� Ten collection pots for the base of the plant towers� 13� One hundred feet of ¾″ diameter galvanized electrical conduit to support
the plant towers� 14� Various lumber or ¾″ square steel tubing to build a support stand for the
towers to keep them above the level of the nutrient reservoir� 15� One hundred feet of 1″ thin wall PVC for the sleeve over the conduit pipe to
permit easy rotation of the plant tower� 16� Ten rotation disks of ¼″ thick by 3″ × 3″ square plastic plate� Drill ¾″ hole
in center to permit conduit to pass through it� 17� Bulk-head sealed fitting for each collection pot or tray to connect ½″ black
poly line to return pipe�
First construct a supporting frame 24″ wide by 20″ high by 114″ long for the plant towers with the nutrient reservoir positioned underneath or in the center as shown in Figure 13�26� Attach a vertical member every 38″ along the length� Put braces on the end portions of the frame as shown in Figure 13�3 for the raceway system� The plant tower can be either set on top of the drain pipe as shown in Figure 13�27, or it can be set beside the drain pipe with a small hose line attached from the collection pot to the return pipe� If the plant tower is set beside the return pipe, cover the top of the frame with ¾″ plywood� Placing the collection bucket on top of the return pipe requires a sealed drain nipple from the bucket to enter the return pipe� Place the bottom end of the conduit in the collection pot to the side of the drain nipple after sliding the swivel plate and a 10″ long 1″ diameter PVC sleeve over the conduit as shown in Figure 13�27� This piece of pipe must be the same length as the height of the
collection pot or one inch shorter so that the tower will drain into the collection pot� Assemble the plant towers using the steel conduit and the 1″ PVC sleeve� Then, slide the special (Vertigro) Styrofoam pots over the conduit with its sleeve�
Stack the pots so that each is rotated by 45° to the one below and set them in the special locking indentations� Use a maximum of seven pots per tower� Put a 1″ diameter PVC tee at the top of the conduit and fasten the tee to ceiling with pipe strapping or other type of bracket� To permit disassembly of the plant tower remove the bracket holding the tee and slide out the remaining plant tower assembly� Once all of the plant towers have been placed at 2 ft centers, start on the irrigation and drainage system�
From the pump in the solution reservoir attach a ¾″ main using the male adapter, tees, and elbows to a bypass line as was shown in rockwool culture (Figure 13�22)� Past the bypass return line with the ball valve, continue the header up to within 2″ of the ceiling where a ¾″ × ½″ slip-thread adapter is connected to a tee at the top� Connect ½″ black poly hose to the ½″ barbed adapters of the tee going both directions to the plant tower rows� Support the PVC tee with a pipe strap or other bracket to the ceiling� The black poly hose attached to the barbed adapters passes through the 1″ tees at the top of each plant tower support pipe and is then plugged at the end using a figure “8” adapter or a short piece of 1″ pipe� Punch three holes in the black poly hose close to each tower and insert the emitters and then the drip lines to them� Two lines go to the top pot and the other one goes to the center pot of each tower�
Attach the bulk-head fitting to the lower side of each collection pan and connect it with a short piece of ½″ black poly hose to the 2″ return pipe to the solution tank� Be sure that the return pipe is lower than the base of the collection pan so that all solution will drain back from the pan to the return pipe by gravity� Alternatively, use a sealed ½″ or ¾″ PVC nipple on the bottom of the collection pot to enter the return pipe located immediately below as shown in Figure 13�27� The return pipe is plumbed back to the top of the solution reservoir as shown in Figure 13�26�
Fill the pots to within 1″ of the base of the adjacent upper pot with substrate of your choice depending upon the crop grown as outlined in the table of Chapter 15� Start herbs by seeding directly into the substrate of the pots� When seeding herbs be sure to use 8-10 seeds per corner planting site� With basil, bok choy, and arugula start the seeds in growing cubes and transplant to the pots after a few weeks� With strawberries you must purchase pre-chilled plants or bring in runners from your garden in the fall or early spring as they must go through a dormancy period� Start up the system to check for any leaks if these plant towers are located in your house as all solution must be contained to prevent damage to your floors�
