ABSTRACT

There is a great variety of hobby indoor hydroponic systems in the market� All hydroponic systems, whether hobby or commercial size, can be placed within two groups according to their circulation of the nutrient solution� One is the recirculated or closed system; the other is that which is a nonrecycled or open system� Clearly, indoors in your home you must use a recirculation or a waste water collection system to prevent flooding your basement or other location having the hydroponic facility� In terms of nutrient management, recycled systems are more challenging than open systems� This is due to shifts in pH and nutrient levels of each element within the nutrient solution� Plants do not take up all elements at the same rate or quantity, especially under varying environmental conditions� As a result, each essential element in the nutrient solution changes with time at differing rates� This causes shifts in pH and the total salts in the solution measured by electrical conductivity (EC)� However, in small household units when you find large changes in EC occurring you can simply dump the old solution (use it on your houseplants) and make up a new batch� The pH can easily be adjusted at any time with an acid or base as described earlier in Chapters 7 and 9�

Open systems are easier to manage since each irrigation cycle adds new solution� You must add sufficient solution to get some leachate as was discussed in Chapter 6� To overcome problems of disposal of the leachate (drainage) during each irrigation, simply place the growing units above a collection pipe that can conduct the spent solution to a waste reservoir� The waste solution can be used to water your house plants or even outside soil garden� Open systems have the advantage that if a disease got into the system, it would not spread back into the plants as it may in a recycled system�

The following discussion of small indoor units is organized from the most simplified ones to more complex ones� These are all recycled systems� In Chapter 13, larger systems of both recycled and nonrecycled systems are presented�

This is a very simple system using a standard plastic flat (10½″ × 21″) without holes and a compact cell tray insert (Figure 12�1)� These compact cell trays come in many different sized cells or cube partitions� They are readily available in garden centers� You may even have some left over from the last time you bought bedding plants for your outside garden� The best size for growing herbs and small lettuces is either a “24” or “36” cell tray� Cut out one corner of sufficient size to fit a plastic 1-gallon container� The plastic container must have a large lid of about 4″–5″ in diameter� Drill a ¼″ diameter hole in the middle of the lid and glue a ¼″ wide cork ring of 3″ in diameter� If you cannot find such cork rings, you may purchase a sheet of ¼″ thick cork and cut one from it� Remove a small gap from the ring, about ½″, so that it is not complete (Figure 12�2)� This gap is going to allow the solution to flow from the bottle to the bottom of the tray� Place your finger on the hole in the lid after filling the bottle with nutrient solution and invert it into the corner of the flat where the corner of the cell tray was removed� Solution will flow from it until the level in the tray reaches the level of the hole in the lid� From then on, it will automatically siphon whenever the solution level in the tray falls below the lid face allowing air to enter the bottle� Refill the solution bottle as it empties from the plants’ water demand�

Use either perlite or vermiculite or a mixture of 20% peat with 80% of either perlite or vermiculite as the substrate� Place the substrate in the cell tray; water it with a watering wand or watering can to thoroughly moisten the medium prior to sowing the seeds� You must use raw water only until germination of the seeds takes place and

the seedlings form their first true leaves, then use a half-strength nutrient solution for the next few weeks before using full strength solution� Do not use the inverted bottle reservoir in the tray until the seedlings are ready for the nutrient solution� You must harvest the herbs, basil, arugula, and lettuce fairly small otherwise they will extend due to the tight spacing restricting light to each individual plant� These types of crops would normally be for 4-6 weeks depending upon their nature of growth� The tray may be used to grow mesclun mixes of baby lettuce, herbs, arugula, beets, mustards, mizuna, chard, and spinach�

The wick system is an old system, but it works, especially for individual pots� This is a very simple form of hydroponics� It can be set up as a single pot or a series of pots or a tray of medium sitting on top of a nutrient reservoir (Figure 12�3)� One or more wicks are positioned in the substrate and hang down into a reservoir of nutrient solution below� Capillary action moves the solution from the reservoir to the base of the plants as the medium dries� Use cotton or nylon fibrous rope� Bury one end of the wicks in the substrate close to where the plants are growing and let the other end dangle down into the nutrient reservoir below� It is best to flare the ends of the wicks to get better uptake and distribution of the solution� The choice of medium to use in this system is a 50/50 mixture of perlite and vermiculite�

These are any simple systems whereby no electricity is needed for pumps or other components� It is simply the addition of nutrient solution to the growing unit by raising and lowering of a tank during an irrigation cycle (Figure 12�4)� This can be done by hand� When the reservoir is raised, the solution will flow from the tank

to the plant tray and when the reservoir is lowered below the level of the growing bed the water will drain back into the tank� This technique is a flood and drain system� The frequency of irrigation cycles depends upon the nature of the growing substrate� You may use perlite alone, a mixture of perlite and peat (50/50), perlite and vermiculite (50/50), peatlite mixture, coco coir mixture, gravel, pebbles, coarse sand, scoria, or expanded clay� The finer the material, the less irrigation

cycles needed per day� With peatlite or coco coir alone, one irrigation per day would be sufficient�

This same principle may be applied to growing herbs, lettuce, arugula, basil, and even flowers in vertical sacks (Figure 12�5)� Sacks are constructed of 6-mil layflat polyethylene that will give a diameter of 6-8″ when filled with a substrate� Cut the sacks about 6 ft long� Tie the bottom with string and fill the sack with moistened peatlite or coco coir� To make it lighter make a mixture of 70% coco coir and 30% rice hulls�

This medium must be moistened prior to placing it in the sack as water will not wet the dry substrate thoroughly when placed in the sack� Break up the peat or coco coir and mix it with some water in a wheelbarrow� Add a little water at a time and mix it uniformly� Test the moisture level in the medium by taking a handful of it and squeeze it until you see a small amount of water coming out� When you release pressure on it, the ball of medium should slightly break apart, but not collapse� At that point you have adequate water incorporated into the substrate� Be careful not to add

too much water� That would be indicated by the ball not breaking slightly and excess moisture draining through your fingers upon squeezing it�

Once you fill the sack, tie the top of the sack leaving about 10″–12″ empty� Fold this end over and tie it again back to the sack� This will allow a loop by which you can support the sack to a frame above with a hook or rope� Use a 2 L (1/2 gallon) plastic water bottle as the solution reservoir� Cut a hole in the top of the sack immediately below the tie of the string� Insert the neck of the bottle in the sack through the hole� For a collection tank use a pail or plastic container with a top� Make some holes in the top of the lid and place it directly under the sack drain end� To irrigate take the water from the collection tank and fill the top irrigation bottle letting it percolate through the sack� Replace the collection pail under the sack to reuse the solution� Of course, as the plants use the solution you will need to add more new solution to the fill bottle�

Cut 1″ holes in the sack going down the sack spacing them at 6-8″ depending upon the crop you wish to grow� Use closer spacing for smaller plants� Stagger the position of the holes to improve light penetration to the crop� Start seedlings in rockwool or Oasis cubes and transplant to the sacks once they are about 2″ tall (usually 3-4 weeks old)�

You can do this same vertical culture using 6″ diameter polyvinyl chloride (PVC) pipe instead of the plastic sacks (Figure 12�6)� Cut 1″ holes in the pipe for the transplants similar to that for the sacks� However, it is best to use 1″ 90° elbows for the plant sites as shown in Figure  12�6� This will support the plants during transplanting� The PVC pipe can sit on a collection pipe of similar diameter that would conduct the solution to a tank� Cut the collection pipe in half lengthwise and fill it with gravel substrate to permit unobstructed drainage to the collection tank� The vertical pipe can also be supported by the collection pipe with additional support to secure its position at the top� Place a one-gallon plastic bottle on top of the pipe�

Remove the bottle cap from the container and invert it into the top of the growing pipe� You can use this fill bottle as a funnel or simply keep it as a storage bottle with nutrient solution that you collect from the drainage of the vertical grow pipe�

In the preceding systems of sack and column culture, a substrate is used to grow the plants�

These sack and column culture systems can be fully automated by having a nutrient reservoir underneath with a submersible pump operated by a time clock� Such automated systems with their plumbing are shown in Figures 12�5 and 12�6� The column culture system may also be set up as an aeroponic method without any substrate� In that case, the nutrient line will have mist jets every 6″ along the pipe opposite the plant sites� The pipe may be installed inside the column or outside entering the column from above as shown in Figure 12�6 as alternative piping� If the column is used with a substrate, the outside plumbing method would be used with drip lines at the top of the column similar to the sack culture system� The plant sites should be arranged spirally down the column at 6-8″ centers�

Both sack culture and column culture are suitable only for low-profile plants like lettuce, arugula, basil, and herbs�

If you wish to grow lettuce, arugula, basil, and some herbs, a simple raft culture system may be constructed� With this system construct a bed from concrete blocks or treated wood� The blocks can be 4″ thick by 8″ by 16″� Place them on edge to get an 8″ depth of the bed� Make the inside dimensions several inches wider on each side of a 4 ft × 4 ft frame� Line it with 12-mil polyethylene (black) or a 20-mil thick vinyl swimming pool liner� Fold the inner corners up like an envelope and glue these laps, if vinyl, using vinyl cement� If using polyethylene bring the liner onto the top of the cement blocks and hold it down with a perimeter piece of lumber� If you use 2″ × 8″ treated lumber, you can staple the liner to the top of the lumber and then nail a lathe around the perimeter to secure the liner edge uniformly�

Purchase a 4 ft × 8 ft × 1″ thick Styrofoam� Use the pink or blue “Roofmate” denser material as it will not break as easily as the less dense white material� Cut the board into 4 ft × 4 ft� Using a saw hole drill cut holes of ¾–7 8″ diameter so that the grow cubes (rockwool or Oasis) will fit snugly into the holes during transplanting� The holes are spaced 6″ × 6″ center to center� Make up nutrient solution to fill the raft bed to within 1″ from the top� The volume of water in this size of bed is as follows:

Volume = length × width × height V = 4 ft × 4 ft × 7″/12″ = 9�33 cubic feet Conversion to U�S� gallons: 1 cubic ft = 7�48 gallons Therefore: 9�33 × 7�48 = 70 gallons

Start your seedlings as explained in Chapter 14� Upon transplanting the seedlings to the raft system aerate the solution several

times a day by beating the solution with a whisk� Alternatively, of course, you could add an air pump with a tube attached to an airstone in the bottom of the bed�

There are two main water culture systems, raft or floating and nutrient film technique� In this section the raft system is presented� This system is ideal for lettuce, arugula, basil, mint, watercress, and a few other herbs� It is not suitable for vine crops or long-term plants due to eventual lack of oxygenation to plant roots� A small indoor unit can be constructed of the following components�

1� A plastic storage bin with lid for keeping clothes or other items is great for a nutrient reservoir (Figure 12�7)� Use a large one at least 14″ wide by 18″ long by 8″ deep, between 12 and 15 gallons� It must have a relatively flat lid and the bin should be of an opaque color such as black or dark blue to prevent light from entering� If light comes in contact with the nutrient solution, algae will grow in it causing plugging of lines and unwanted build-up of slime in the system� Also, you can wrap the bin with aluminum foil to

prevent light and heat accumulation� The plants are seeded in rockwool or Oasis cubes and within 3 weeks transplanted to 2″ diameter net pots that support the plants in the lid of the storage bin (nutrient tank)�

Alternatively, use storage or tote bins without a lid and cut a 1″ thick Styrofoam board to float on top of the solution (Figure 12�8)� Prepare it as described earlier in “Manual Systems�” Be sure to use the dense “Roofmate” type of Styrofoam� Cut ¾″ holes spaced 6″ × 6″ for lettuce, arugula, and basil� For smaller herbs make the spacing 4″ × 4″� The use of the Styrofoam cover over a plastic lid is that it insulates the solution below, but that should not be an issue if this is for growing plants inside your home under artificial lights�

2� An air pump, such as a fish aquarium pump with plastic tubing� 3� A fish aquarium airstone attached to the other end of the tubing� This is

located in the nutrient reservoir to add oxygen to the solution� You may purchase this equipment at a pet store where fish and aquariums are sold� Use an airstone 4-6″ long to give lots of oxygen to the nutrient solution� Assembly is shown in Figures 12�7 and 12�8�

The principle of the NFT system is to keep a constant flow of thin layer of solution through the plant roots in a channel or grow tray� This is a recirculation method returning the solution from the grow tray back to the nutrient reservoir below� The components are as follows�

1� One or two grow trays or gutters constructed from a 2″ PVC pipe� There are commercial NFT channels available at hydroponic stores� If you want

to use a 2″ PVC pipe, you will need the following fittings for each channel: one end cap, one 2″ 90° elbow with a 2″ × 1″ reduced bushing, 4″ of 1″ PVC pipe as the drain spout back to the reservoir underneath� If an elbow is used one end cap will be sufficient� However, it would be better to use one 2″ × 1″ reduced tee just before the end of the pipe and another end cap� That would be more effective than using the elbow and reduced bushing at the drain end of the pipe� Then, the end of the tee with the added 1″ spout would enter the lid of the reservoir�

2� Purchase a small submersible pump, such as a “Little Giant” fountain pump or a smaller submersible pump, at a hydroponic or irrigation store� Poly tubing to connect the pump with the inlet end to the growing channel� Drill a small hole on the top of the pipe at the front end where the solution will enter�

3� A nutrient reservoir of a storage bin as described earlier in “Floating System�”

4� An aquarium air pump and airstone as was also described in “Floating System�”

5� Small 2″ × 2″ round plastic mesh pots available at a hydroponic shop� These are needed to support the growing cube with the transplant� During transplanting place the seedling in the mesh pot, which sits in the hole in the growing channel�

1� Drill one small hole in the storage bin lid near one end and the other at the opposite end� These must be just large enough to fit the poly hoses from the pump in the nutrient tank going to the NFT channels and the other from the air pump to the reservoir connecting the airstone�

2� The NFT channels will need 2″ diameter holes drilled at the plant spacing of 6″ or 4″ according to the crop spacing needed� Be sure that these holes will not cut the sides of the pipe� These plant holes are to fit the 2″ net pots with the transplants as shown in Figure 12�9�

Keep all the holes in line at the top edge of the pipe� Do this by snapping a chalk line along the top� Once the holes have been drilled, use sandpaper to eliminate all sharp edges of the holes� Then, glue an end cap at the inlet end and a reduced tee (2″ × 1″) before the end cap at the drain end of each channel�

3� Drill a 1¼″ hole in the reservoir lid at the return end of the NFT channels to allow the 1″ diameter tee and spout to enter the tank for drainage back to it�

4� Make a support pipe to be placed at the top edge of the grow pipes� This is done by using a short piece of 3″ PVC pipe and cutting 2″ holes in it to hold the grow pipes� Be sure that in this case the 2″ or slightly larger holes will cut the side of the support pipe to permit the nesting of the grow pipes� This can be done with a hole saw and then widen the edges with a hacksaw until the grow pipes nest securely� You could also use a short piece of 4″ diameter pipe to do this as the support pipe� The principle here is to support one end

of the growing pipe at least 2″ above the lid of the reservoir underneath� This will give adequate slope so that the solution will quickly run back to the nutrient reservoir giving the solution some oxygenation as it falls back into the reservoir� Simply lay the support pipe on top of the reservoir lid at the inlet end of the growing pipe as shown in the plan view of Figure 12�10�

The flow of the nutrient solution should be between 1 and 2 L (¼–½ gallon) per minute� That rate of flow will provide good oxygenation� If you use ¼″ tubing from the pump to the channel insert a small piece of drip line into the end where it is entering the channel to reduce the flow, if necessary�

The final assembly will appear as in the diagram (Figure 12�10)�

This system consists of a growing tray sitting above a nutrient solution reservoir� The principle here is to flood the growing tray with the nutrient solution and then allow it to drain back to the reservoir below� Substrate should be porous such as gravel, pea gravel, expanded clay, or coarse sand� Do not use any fine medium like peatlite, coco coir, or sawdust as these will hold too much moisture and there will be a lack of oxygen to the plants�

A submersible pump in the solution reservoir pumps the solution into the tray� The pump is operated by a timer to automatically irrigate several times a day depending on the stage of plant growth and moisture retention of the medium� A sealed fill/drain fitting must be attached to the bottom of the grow tray� When the timer shuts off the pump, the solution will run back to the reservoir below through the pump�

This type of hydroponic system can grow most plants including vine crops of tomatoes, peppers, eggplants, and cucumbers�

1� Two storage bins, one for the nutrient tank and the other for the growing tray� The growing tray may be larger than the solution reservoir, but should be shallower� A large grow tray would sit on top of the solution reservoir�

Use at least a 15-20 gallon bin for the reservoir with a depth of 1 ft or more� The grow tray should be wider and longer in order to sit above the solution tank supported by ¾″ square metal tubing spanning the reservoir (Figure 12�11)� The depth of the growing tray should be 8-10″� A second option is to have the length and width of the growing tray slightly smaller than that of the reservoir enabling it to nest within the reservoir as shown in Figures 12�12 and 12�13�

2� A frame to support the growing tray may be constructed of 1″ schedule 40 PVC or ¾″ square steel or aluminum tubing that could be cut and bolted together with brackets or if the reservoir bin is strong enough, simply place a few square steel tubing bars across it as shown in Figure 12�11�

3� A submersible pump with ½″ polyethylene tubing� 4� One bulk-head fitting to seal the entrance of the tube from the pump into

the bottom of the grow tray� Bulk-head fittings have rubber washers on each side and screw tightly against the tray to seal it from leaking� Alternatively,

you could use some air-hose fittings available in an aquarium shop� Seal those with silicone rubber�

5� An overflow pipe that regulates the maximum height of the solution entering the grow tray� This pipe should be long enough to regulate the solution level within 1″ from the surface of the substrate in the grow tray and extend below into the solution reservoir to avoid any spillage� It must also be sealed with some type of fitting similar to the pump inlet tube�

Assemble the ebb and flow system as shown in the diagrams (Figures 12�11 through 12�13)� Probably the most difficult parts to install are the inlet pipe and overflow pipe in the bottom of the grow tray so that a water-proof seal is attained� The construction of the support frame for the grow tray must maintain the grow tray level in all directions above the nutrient reservoir� Be sure to wrap the reservoir with aluminum foil to prevent light from entering� Also, purchase a lid for the storage-bin reservoir� Make an access panel of 2″ × 2″ at one corner of the lid to enable the addition of water to the tank�

When mixing the nutrient solution remove the lid of the tank, pump, and fittings and slide the tank from underneath the growing tray� It is important to construct the frame of the growing tray high and wide enough so as not to restrict movement of the reservoir below for making up the solution� When the plants use up about half of the nutrient solution in the reservoir add water only the first time, and the second time it goes down change the solution� Clean the reservoir well with a 10% bleach solution to disinfect it and then rinse it with clean water before making up the solution�

This ebb and flow system can be modified to use pots with substrate instead of a full tray of aggregate� To construct this system use a grow tray of 4-6″ deep instead of 8-10″� Place 1″ of aggregate in the bottom of the grow tray to prevent algae growth in the tray� Set three-gallon nursery pots on top of the gravel in the tray as shown in Figure 12�11� Fill the nursery pots with coarse sand or perlite� The rest of the growing tray is made similar to that described earlier with the exception that the overflow pipe is set 2″ high above the base of the tray� The remaining components are the same�

Drip irrigation is the most widely used and versatile method of hydroponics� Operation is simple with a timer activating a pump to initiate an irrigation cycle� During a cycle of irrigation, the solution is pumped from the nutrient reservoir to the base of the plants through a drip line (Figure 12�14)� Drip irrigation systems may recycle the nutrient solution to the nutrient tank or it may leach to waste� In a recirculation (closed) system the pH and strength (EC) of the solution must be checked periodically and adjusted� As a result, the recycled system is more complicated to manage compared to an open system in which the excess solution drainage (leachate) is run to waste� In the nonrecovery design, the nutrient solution is made up and applied to the plants during irrigation cycles with the same pH and concentration without needing adjustments� The nutrient solution may be stored in a large cistern or tank� It can also be mixed as concentrated “stock” solutions that are diluted by

an injector system upon demand for an irrigation cycle� This is the most common method for large hydroponic operations� For indoor hobby units simply make up a batch of nutrient solution in a storage tank� The larger the tank the less frequent will be its makeup�

Suitable substrates include peatlite, coco coir, perlite, vermiculite, sawdust, rockwool, rice hulls, and expanded clay� Any of these will grow most plants including the vine crops� The basic setup is very similar to that of ebb and flow systems with the exception that the nutrient solution is pumped to the base of the plants at the top of the tray and distributed with a drip manifold to individual drip lines (Figure 12�14)� The solution is returned to the tank underneath by a drain pipe sealed to the bottom of the grow tray� The growing tray must be level in all directions to prevent any water accumulation� An option to fill the grow tray with medium is to use pots in the tray� Set them on top of a black weed mat or on about 1″ of gravel or expanded clay to facilitate drainage and to prevent algae growth� The size and number of pots is dependent upon the crop grown� For lettuce and herbs use eight 4″ pots� For vine crops a maximum of two 10″ pots is feasible providing the plants are V-cordon trained in both directions� In this manner, separate the top of the crop sufficiently to get 3�5 sq ft of surface per plant� Place two drip lines in each pot� It is advantageous to include an air pump connected to an airstone placed inside the solution tank to improve oxygenation�

1� Two plastic storage bins as described earlier for the ebb and flow system� The grow tray should be 8-10″ deep so that there is adequate space for growing vine crops�

2� PVC or steel pipe framework to support the grow tray above the solution reservoir�

3� Submersible pump with tubing, drip manifold, drip lines, and stakes to hold the drip lines in place�

4� An aquarium air pump placed outside, connected with poly tubing to an airstone (4-6″) in the solution tank�

5� A ¾–1″ diameter drain pipe attached flush with the bottom of the grow tray on one end using a bulk-head fitting or other that gives a complete seal against leaking�

6� A time clock to control irrigation cycles by the pump�

The assembly as shown in Figure 12�14 is very similar to that of the ebb and flow system with the exception of the different placement of the drain pipe and the use of the drip lines to the top of the grow tray� Drip irrigation supplies may be purchased from an irrigation or hydroponic store or online�

Seedlings are started in rockwool cubes, transplanted to blocks (vine crops), and later transplanted again to the grow tray once they are 6″ or so tall� The procedures for growing seedlings are discussed in Chapter 14�

One of the very earliest indoor units using drip irrigation was that of the “tube-intube” design as was shown in Figure 1�2 of Chapter 1� A fish aquarium air pump is mounted on one edge of the growing tray with a ¼″ diameter poly hose connecting it to a slightly larger diameter hose in the nutrient solution of the reservoir underneath� The key to success here is to use a slightly larger hose to join about 1″ insertion of the smaller diameter hose allowing the air to suck in the nutrient solution as it enters the larger hose� Connect the larger tube to the smaller one with a pin� The larger hose must be loose enough for the solution to enter at the union as the air is bubbled up through the larger hose� The movement of air drags the nutrient solution into the larger tube and raises it up into the grow tray above� The larger hose enters the grow tray and lies on the top of the substrate� This area of the hose above the substrate has small holes drilled into it every 2″� The holes must be no larger than 1 16″ in diameter so that all of the nutrient will be carried along its length on the top of the medium�

To support the grow tray without a tray support frame do as follows: Purchase the grow tray a few inches smaller in length and width than the reservoir� Drill ¼″ diameter drainage holes in the bottom of the grow tray 3″ × 3″ spacing to within 2″ of the outside perimeter� Do not use a lid on the reservoir below� Place two or three ½″ square aluminum-or chrome-plated supports across the top of the nutrient tank and set the grow tray on top of those bars in a position between the drainage holes� To use a lid on the lower tray, it is possible if it has a lip that seals the bin around the edges� However, to get good drainage position the upper grow tray on top of the lid of the lower reservoir and drill holes through both the bottom of the grow tray and the lid of the reservoir at the same time in the identical same positions� Glue or silicone a few guides, using small plastic tubing, positioned at the corners of the grow tray and adhered to the lid of the reservoir� In that way, when you place the grow tray on the top of the reservoir, the drainage holes will line up� Refer to Figure 1�2 to follow the assembly of the drip systems�

The air pump can be activated with a time clock for the use of fine substrates in the grow tray or for coarser material such as rocks or pebbles allow the pump to run constantly� The air pump not only moves the solution from the reservoir below, but also adds oxygen to the solution as it moves up to the grow tray�

For this form of drip system, you may use expanded clay, pea gravel, coarse sand, perlite, vermiculite, or rockwool granules� Do not use peatlite mix or coco coir due to excessive moisture retention� You could use rice hulls as they have lower water retention� Coarse vermiculite and perlite are the best substrates for this system� If you wish to use pea gravel or expanded clay add a ½″-thick layer of peatlite or coco coir layer on top to achieve capillary sideways movement of the solution�

Rockwool is a common substrate used in hydroponic culture and it is available at hydroponic stores� As discussed in Chapter 14, the seedlings are started in

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rockwool cubes that are transplanted to rockwool blocks� From there, they are transplanted to the rockwool growing system using rockwool slabs 4″ thick by 6″ wide by 36-39″ long� The simplest method of construction for an individual unit is to purchase a plastic bin of minimum length of 36″ by 18″ wide by at least 8-10″ deep (Figure 12�15)� A greater depth is fine as that will increase the overall volume of the tank and reduce the frequency of adding water and/or changing the solution� If you can find this size of container, a second grow tray above will not be necessary providing the tray has a locking lid that positions the lid top below the sides of the bin� If such dimensions are not available use two bins as described for the drip irrigation system�

Use the lid as the support tray for the rockwool slabs� With the preceding dimensions of the bin, the system will fit two slabs� Feeding of the plants to their bases is by a drip irrigation system operated by a timer� As described for drip irrigation systems, position the end of the drip line with a special barbed stake guide� There are several differences with this drip system compared to the ones described earlier� The pump is connected to PVC pipe that is converted to ½″ black poly hose using a barbed adapter at the entrance to the slabs above the lid� The black poly line runs along the length of the lid between the two slabs� Drip lines are attached to the black poly line using 0�5-gallon per hour pressure compensating emitters punched into the line� Each emitter is attached to a 16″ length of drip line of 0�160-0�220″ diameter�

With vine crops such as tomatoes, peppers, cucumbers, or eggplants, each slab will contain three plants so a total of six drip lines are required, one to each plant base� The end of the black poly hose is bent over and secured with a figure “8” adapter or a short 3″ piece of 1″ diameter PVC pipe� The key to success with this number of plants is the V-cordon training in both directions to provide 3�5 sq ft per plant at ceiling height� Plant only one cucumber plant per slab�

1� One plastic storage bin with a lid measuring 36″ × 18″ × 8-10″ or more in depth�

2� Submersible pump of minimum capacity of 80 gallons per hour (gph)� 3� Compensating emitters of 0�5 gph� 4� Drip line-0�160-0�220″ diameter, 10 ft� 5� Barbed stakes: six� 6� Figure “8” end stop or 3″ of 1″ diameter PVC pipe� 7� Schedule 40, ¾″ diameter PVC pipe: 2 ft� 8� Male adapter to fit pump outlet diameter, a reduced bushing from ¾″ diam-

eter to the diameter of the pump outlet� 9� Fittings: ¾″ PVC 90° elbow, ¾″ × ½″ slip by thread bushing, ½″ barbed

adapter (thread-barb), 1″ hose clamp� 10� PVC glue and cleaner 11� An aquarium pump, poly tubing, and 6″ airstone to aerate the solution� 12� A 24-h time clock with 5-15 min intervals, no greater� 13� A poly punch tool to make the holes in the black poly hose for the emitters�

First assemble the drip hose and emitter system� Glue the various fittings, punch the holes for the emitters (six for vine crops) evenly along the length of the black poly hose starting at 3″ from the PVC adapter and no closer than 6″ to the end� Push in the emitters and attach the drip lines with the barbed stakes at their ends� Then, make up the PVC piping from the pump to the black poly lateral hose� Use Teflon tape on all threaded fittings� Refer to the diagram for details�

With the air pump attach a section of poly tubing long enough to reach the inside of the reservoir and there connect to the airstone�

Make ¼″ drainage holes on the top of the lid for recycling the solution leachate from the slabs to the reservoir below� Make two rows of these holes about 4″ apart going down the center of the lid and within 1½″ of the edge� Drill the two rows of holes 4″ apart and stagger their positions (Figure 12�16)� At one end make holes 4″ apart to intercept any runoff that does not go down the center of the lid�

Drill a hole large enough to fit the PVC pipe from the pump in the middle of the opposite end to the drain holes, 3″ from the edge of the reservoir� Construct a little stand about 1″ high at one of the corners of the lid to support the air pump� Drill a ½″-diameter hole for the air hose to enter the reservoir to connect to the airstone� Cut a 3″ × 3″ square access panel in the lid at the middle or corner of one end to permit the addition of water to the reservoir� Refer to the diagrams for details (Figures 12�15 and 12�16)�

If you cannot find a storage bin 36″ long, design the system as explained earlier, but cut the rockwool slabs shorter to fit the lid dimensions� It may be possible to grow only four vine crops in such a smaller unit� If you cut the end of a slab staple it closed�

When growing vine crops that are trained vertically in a small hydroponic unit support them above with a wire and space this wire to give adequate light to the entire plants as explained in Chapter 24� V-cordon train them away from the grow tray� The support cable must be at least 30″ apart at the top of the mature plants� In your basement or a spare room use ceiling hooks to support the plant strings�

This system is the very same as the rockwool one, but instead of using rockwool slabs, use coco coir slabs� The dimensions of the coco coir slabs are similar to those of rockwool� The biggest difference in cultural techniques is that coco coir needs less frequent irrigation cycles compared to rockwool� Generally, two to three cycles per day are sufficient� You need a 15% leachate during each irrigation, whereas with rockwool the leachate should be 20%–25%�

An aeroponic system is one of the most highly technical methods of hydroponics and most risky should a loss of power occur to delay irrigation cycles� In this system, the plants are supported in the top (lid) of the reservoir with their roots suspended below in the air space between the solution and top cover� The roots are misted every few minutes with nutrient solution� The submersible nutrient pump is controlled by a timer that runs the pump for a 1 min and 4 min off on a 24-h basis�

The nutrient reservoir should be of 15-20 gallons with a depth of at least 12″� It must come with a lid that secures the sides of the bin� This system is best for small plants such as lettuce, basil, arugula, and herbs, but with care and experience it could grow vine crops� All of the crops are started in rockwool cubes and transplanted to 2″ mesh pots that are placed in 1¾″ diameter holes on the top of the bin lid� For lettuce, basil, and arugula use 6″ × 6″ spacing of holes, and for other herbs you may use 4″ × 4″ spacing� Stagger the position of the holes if possible� The exact layout of the plant holes depends upon the dimensions of the storage bin� For example, a bin 16″ wide by 20″ long by 12″ deep, as shown in Figure 12�17, has a volume of 17 U�S� gallons� It would hold eight plants (four per row) in two rows spaced 8″ apart� The spacing within each row is 2½″—5″—5″—5″—2½″�

1� A 15-20-gallon storage bin (2-2½ cu ft) with lid� 2� A high pressure submersible pump� 3� PVC pipe of ¾″ diameter for the mist nozzle distribution pipe and the sup-

port pipe frame� 4� Various PVC fittings for the mist distribution pipe� 5� An accurate 24-h timer with minute intervals� Alternatively, use two timers,

one of 24-h intervals and the other of 1 h with 1-min intervals� Place these in series�

The pump and all piping are set within the nutrient reservoir� The mist jets mounted in the PVC header pipe is located above the level of the nutrient solution� Assemble the piping and mist jets first then place them in the nutrient reservoir� A supporting

frame of PVC pipe is constructed to support the mist-jet manifold above the level of the nutrient solution�

Cut 1¾″ diameter holes in the reservoir lid at spacing according to the nature of the crop as described earlier� Make a 2″ × 3″ access panel at one corner of the lid to add water or nutrients� The mist nozzles should be located about 4″ below the top of the lid� The maximum level of the solution is to be 6″ to permit adequate air space above for the mist distribution and the aeration of the plant roots� These details are outlined in Figures 12�17 and 12�18�

Use two bins, a lower nutrient reservoir and an upper growing tray� The growing tray should be several inches smaller in length and width from the reservoir so that it will sit flat on the cover of the reservoir� The growing tray should be about 6″ deep with a cover� It sits on top of the lid of the nutrient tank� Install a ½″ diameter drain pipe at the center of one end of the grow tray to return the solution to the tank below� Seal the drain pipe to the bottom of the grow tray as explained earlier for other units�

Use ½″ high-pressure tubing from the submersible pump to the base of the grow tray� As it enters the grow tray use a rubber washer to seal it� Connect the tubing to a ½″ barbed tee as it enters the growing tray� With a short piece of tubing connect both sides of the tee to ½″ PVC using barbed-PVC adapters as shown in Figure 12�19� This will allow the growing tray to be detached during cleaning between crops� In the grow tray, the PVC pipe is branched with the tee to form two mist nozzle manifolds� Insert the mist nozzles at about 6″ spacing along the manifold depending upon the grow tray dimensions� The misting assembly sits on the base of the grow tray as shown in the diagrams of Figure 12�19� Cut holes in the grow-tray cover for the plant

pots as described earlier� Use Schedule 40 or 80 PVC pipe that has thick walls so that the mist nozzles can be attached to the pipe�

Drill ¼″ holes in the lid of the nutrient tank about 5-6″ apart for drainage back to the solution tank of any solution that may leak from the grow tray�

These types of aeroponic units are available at hydroponic shops and online (refer to Appendix)�