Marijuana Grower's Handbook
Page 28
You can adjust the moisture level of LECA by adding vermiculite. The vermiculite breaks apart and covers the pebbles. Use about 1 part vermiculite to 10 parts LECA by volume.
It is made by baking pure natural clay at 2200° F (1200° C) for three hours. As a result the pellets expand into a lightweight, semi-porous medium. It is pH neutral so it doesn’t affect the water/nutrient mix.
LECA provides both moisture and air to the roots using capillary action. The water/nutrient solution is wicked up along the pebble surface. Overwatering and root rot are eliminated due to the space between the pebbles which allows oxygen to get to the roots.
ROCKWOOL
Rockwool is sterile and convenient to set up and remove. It holds together well and is easy to handle if you follow basic precautions. It is made by melting basalt and chalk and then spinning the molten rock mixture in a process very similar to making cotton candy. Long strands are formed and then processed into different shapes, textures, and sizes that vary from 1” (2.5 cm) starter cubes up to 3”x 12”x 36” (7.5 x 30.5 x 91.5 cm) slabs.
Rockwool is constructed so that 18% of the space is reserved for air, even after the blocks have been irrigated to saturation. Water tension doesn’t rise as the material becomes drier, so it is easy for the plant to absorb moisture until it is used up. These two characteristics mean that rockwool retains both water and air, so the roots’ needs for oxygen and water are easily met.
Rockwool comes in many sizes and several forms including cubes and slabs, pellets and as rockwool “wool.”
New rockwool is highly alkaline because it contains residual lime as the result of manufacturing. To remove the lime, soak it in an acidic, 5.1 pH, water solution for 24 hours to dissolve the lime. Adjust the water using pH Down. Then flush the cubes or slabs with nutrient-water solution. They are now ready to use. From this point on, the rockwool has only a slight alkaline value. Adjust the pH of the nutrient-water solution so it is no higher than 6.1 to buffer the medium’s alkaline qualities.
Cubes range from 1” to 4”(2.5 -10 cm). The two sizes of “starter cubes” used for marijuana propagation are the 2”x 2”x 1.5” (5 x 5 x 3.75 cm) unwrapped cubes and the 1.5” square (3.75 cm) plastic-wrapped cubes that slow evaporation. The 4” (10 cm) square cubes are large enough to support small plants. For larger plants, place the starter cubes on top of rockwool slabs or into other growing mediums.
Roots quickly grow from the 4” (10 cm) cubes.
To move plants to larger quarters, place the cube over a 8” (20 cm) slab. The roots will quickly grow into it. Photos above: Angelic C.
Slabs are all 3 inches (7.5 cm) deep and 36" (91 cm) long and come in widths of 6, 8, 10 and 12 inches (15, 20, 25 and 30 cm). The 6”(15 cm) and the 8” (20 cm) width slabs are by far the most popular sizes and are large enough to grow just about anything.
The slabs come wrapped in plastic, which can be left on to prevent algae and other infections. Remove or slice the plastic on the bottom to allow easy drainage, but don’t remove the plastic from the top or sides. To transplant a cube to a slab, cut an “X” the size of the cube in the plastic. Fold up the corners of the “X”, and place the cube directly on top of the slab. The roots quickly grow into the slab and lock the cube in place.
Loose rockwool is another option. It is available with either water absorbent or repellant qualities. Using loose rockwool enables you to fill pots or other containers with the growing medium. Another benefit of using loose rockwool is that you can custom tune your medium to retain just the right amount of water for the set-up.
Use care when working with rockwool. Its dust and fibers pose health risks. They can cause skin rash or lodge in your lungs, causing temporary micro-ulcers. First, wet it down so fewer fibers become airborne. At the very least, wear a mask, long-sleeved clothing, and rubber gloves when working with dry rockwool. When working with loose rockwool, a bodysuit with ventilator is the best protection. Wetting the rockwool before handling reduces dust.
Rockwool is not environmentally friendly. It is hard to dispose of responsibly because it does not decompose, even when buried. Fortunately, rockwool is easy to re-use. Although most home gardeners use it only once, commercial greenhouses growing roses and tomatoes often use the material for one to two years, until it starts to fall apart.
Rockwool cubes can be used to grow large plants and support them through flowering.
To prepare rockwool for reuse, it’s best to let it dry out a bit, so figure on alternating two sets of blocks between crops. Cubes are easily removed, but it’s easier to work with slabs while they are in place. First, pull out stems and roots or cut them off. Then sterilize the rockwool by soaking it in a 3% hydrogen peroxide solution for 24 hours or by using drippers or ebb and flow to deliver the solution to the material. After treating with the hydrogen peroxide solution for 24 hours, rinse the rockwool thoroughly.
HYDRO METHODS
FERTIGATION
Fertigation is the simplest form of hydroponics. The plants are grown in regular planting containers. They are filled with non-nutritive planting mix and watered by hand, drip system or using a capillary mat. Nutrients are supplied using a nutrient/water solution.
Fertigation systems are frequently used in the nursery industry to grow potted plants. They are simple to construct and maintain and can easily be upscaled. Any non-nutritive medium can be used but peat moss and peat moss blends are favored because they are inexpensive, have good buffering ability and have good capillary action.
A reservoir is the simplest hydro system to set up and maintain.
Peat moss and vermiculite-perlite require less irrigation than other hydroponic mediums because they hold more water. Fertigation is often used in conjunction with capillary mats.
PASSIVE HYDRO SYSTEMS
Passive systems use capillary action to draw water through the planting medium. As water is used it creates “tension” which pulls water molecules up. It supplies plants with as much water as they need.
ACTIVE HYDROPONIC SYSTEMS
Active systems use pumps to move fresh water/nutrient solution to the plants so the environment is refreshed by a solution that hasn’t been mined of nutrients and oxygen. There are many types of active systems but most of them fall into one of five categories: deep water culture, drip, ebb and flow nutrient film and aeroponic systems.
THE RESERVOIR SYSTEM
The reservoir system is by far the easiest system to set up and maintain. Plants are grown in ordinary plant containers of the chosen size. The containers are placed in a tray that has walls 4-6 inches (10-15 cm) high.
The containers are filled with clay beads. Alternatively the bottom third of the container is filled with beads and the top portion is filled with a hydroponic mix such as vermiculite-perlite, peat moss (Sunshine Mix #4) or even a non-hydro planting mix. The container is placed in the tray, and sits directly in a hydroponic nutrient-water solution with about 20-25% of the container immersed in the water. Immerse a container with planting mix 4 inches (10cm) high in water 0.75-1 inch (2-2.5 cm) deep. A 12 inch (30 cm) tall container should sit in 2.5-3 inches (6.5-7.5 cm) of water.
The water in the system is circulated using a small pump or aerated using an air pump or bubbler. Its temperature is maintained at about 72˚ F (22˚ C) using an aquarium heater.
This may be the most inexpensive system and the fastest one to set up, and is an excellent technique for use outdoors since the container has its own limited reservoir and can be attached to a larger water source using a float valve.
Make sure to use a light colored plastic cover over the tray to prevent rain from entering and to keep the roots cool.
This technique can be adapted so that containers have their own internal reservoirs, rather than external trays. Fill the bottom 20% of the container with water. A gauge can be placed in the container to measure the water level.
To make a gauge use a plastic tube with some holes drilled in to allow water to enter and exit freely. Place it
vertically in the container and affix it with silicon glue or place the pebbles around so it is held vertically. Take a thin wooden or plastic rod and affix a cork on the bottom using silicon glue. A bamboo stake works well for this. Place the stake in the tube. The cork will float on top of the water, pushing the rod up to indicate water level. Mark the rod so it shows maximum desirable levels. To drain water from the pot remove the rod and insert a small tube attached to a pump or siphon.
It’s important to be as “green” as possible when growing green. The Tray Hugger line of reservoirs available from Humboldt Wholesale is made from 90% recycled plastic and features rounded corners and reinforced sidewalls.
Almost any tray can be used as a reservoir.
Another gauge can be made using a piece of transparent flexible plastic tubing. The tubing is inserted into a hole at the bottom of the container and silicon glue is used to prevent leaks. The tube is attached vertically to the side of the container so it indicates its water level. To drain water, change the tube’s position. Using tubing, several containers can be connected to a single reservoir regulated by float valves.
STEPS TO SETTING UP A RESERVOIR SYSTEM
1.Obtain enough clay beads to fill the containers.
2.Rinse the stones in water until the pH tests close to 7, neutral.
3.Pour the neutralized LECA into appropriate sized containers.
4.Place the containers in the tray.
5.Water the containers from the top to get started. Make sure the planting medium is thoroughly moistened
6.Mix nutrient/water solution and adjust it using meters to test the EC or ppm and pH of the solution.
7.Add a small submersible pump in the tray to circulate the water.
8.If the room temperature gets cool, it may cool the water too much. Add an aquarium heater to the tray.
9.Use a sheet of white/black polyethylene or other opaque cover to place over the tray. The cover keeps light from getting into the nutrient/water solution, where it would promote algae growth.
10. Optional Accessories: water reservoir regulated by a float valve. The water level of this system should be maintained at a fairly stable level. As the plants grow they will use larger quantities of water so it will have to be replaced more frequently as the garden proceeds towards flowering. With an external reservoir the system is automated and does not have to be serviced as long. Water should be added to containers with drains sitting in trays from the top so that any buildup of nutrient salts caused by evaporation gets washed back out of the container into the tray.
This system used a kiddie pool as the reservoir, and a pallet as a platform.
The roots often trail the wick down into the water. Roots that grow in water are thicker and have fewer root hairs, but supply the plant with enormous amounts of water. To keep them healthy, give them plenty of oxygen using a pump or air bubbler to circulate the water.
SUPPLIES AND TOOLS REQUIRED
•LECA (Lightweight Expanded Clay Aggregate)
•pH test meter or pH test paper
•Planting containers
•Tray with walls of the appropriate height.
•Hydroponic nutrient solution.
•EC or ppm meter
•Submersible pump
•Aquarium heater
•Tray cover
•Reservoir (optional)
•Float valve (optional)
THE WICK SYSTEM
The wick system is inexpensive to construct and easy to set up and maintain. The planting container is held above a reservoir. Both ends of braided nylon rope hang from holes in the bottom of the container into a reservoir filled with water/nutrient solution.
The principle that drives this system is capillary action, the same chemistry that draws water up a napkin. As the water is removed from the wick the water molecules above draw neighboring molecules towards them to maintain the electrical charge and ultimately equalize water tension. As a result, with no work on your part, the wick maintains moisture by drawing up water as needed.
The wick is made from braided nylon rope. The diameter of the rope increases with the size of the container.
An ordinary nursery container, a bucket or even a soil bag can be used. Before the container is filled with planting mix, install the wicks in the container. They should be long enough to stretch from the bottom of the reservoir through the bottom or side hole of the container, then exit the hole on the other side and run down to the bottom of the reservoir. Each container should receive two wicks at 90˚ angles.
Keeping the holes in the container small makes it difficult for roots to penetrate to the reservoir. Keeping the roots from growing down the wick into the reservoir may be a matter of convenience. However, once the roots hit the water, both their growth and the growth of the plant spurts because the roots now have access to cheap water and nutrients.
The wick system is self-regulating; the amount of water delivered depends on the amount lost through evaporation or transpiration. More than monitoring the containers to check to see that they are moist, with the wick system the main thing is to keep your eye on the reservoir. As long as the reservoir has water, the plants are being watered.
A number of different mediums can be used as planting mixes for wick systems, but virtually any planting mix can be used since soils generally draw water. Using a planting mix has the advantage of providing the plants with a nutrient-rich base that can be supplemented using a water/nutrient solution. If the medium does not seem to be drawing water and is too dry, adding 20% vermiculite to the mix will add drawing capacity.
A mix consisting half each vermiculite and perlite provides a non-nutritive medium that is easy to work with and has a nice consistency and draws water well. Using vermiculite-perlite allows you to have complete control over the nutrients being supplied to the plants. Adding 10% worm castings or compost increases the microbial life and provides a substrate for them to thrive. Their symbiotic relationship with the roots increases plant vigor and growth.
Each medium has a maximum saturation level. Beyond that point, an increase in the number of wicks does not increase the moisture level.
Wick systems are easy to construct. The wick should extend from the container to the bottom of the reservoir. Supports keep the containers above the level of the water in the tray. Cement or wooden blocks and pallets make good supports. Place the containers on the blocks. Make sure the wicks are touching the bottom of the tray. Fill the tray with nutrient/water solution. Replace the water in the tray as it evaporates or is absorbed by the medium through the wick.
You can construct variations of wick and reservoir systems using two planting containers such as five gallon (19 l) buckets. One container should fit inside the other. The bottom container, which has no drainage holes, will be the reservoir. It is fitted with a support on the inside bottom that keeps the upper container from fitting tightly into it. This keeps the containers from locking tightly, ensuring that they come apart easily. A block of wood or Styrofoam or even a rock can be used for this purpose.
Nylon starts to unravel when cut. Bind the ends together by heating the end with a jet flame, or use silicon glue.
CONTAINER DIAMETER ROPE DIAMETER
Up to 6” (15 cm) .25” (0.6 cm)
8-9” (20–22 cm) 3/8” (1 cm)
12–15” (30–38 cm) 5/8” (1.5 cm)
15”+ (38 cm +) 3/4–1” (2–2.5 cm)
If the unit is to be used outdoors drill holes in the outer container just below the level where the inner container will rest. These overflow holes prevent waterlogging of the upper container should it rain. Placing a cover over the container prevents water from entering.
Fit the inner container with wicks, place it in the reservoir container and fill it with planting mix. Using these closed systems rather than containers with drain holes that let water escape conserves water and requires less frequent irrigation.
The unit can be fitted with a water level gauge as described above.
It is easy to automate individual buckets so they are self-watering. Tubes connect several bottom containers to a reservoir regulated by a float value. The valve is adjusted to close when the water reaches a height about 0.5 inch (1.25 cm) below the bottom of the growing containers.
The automated wick system requires no power. Water siphons into the growing buckets as it is needed. To get the siphon started, the valve container is primed and raised above the level of the individual trays. Water flows from the valve to the plant trays as a result of gravity. Once the containers have filled and displaced air from the tubes, the water siphons automatically.
A simple system can be devised using a plastic kiddie pool and a shipping pallet. Place the pallet in the pool. Install wicks in the containers and place them so they sit firmly on the pallet. Fill the pool with water/nutrient solution up to the bottom of the pots. The wicks move the water to the pots automatically as needed.
Reservoir and wick systems are available from several manufacturers. They require no moving parts and are reliable, although much more expensive than homemade ones, which are simple to make. Although these systems are denigrated to an extent by industry because they are so simple to construct and maintain, they supply all the plant needs and are high producers. In addition they are much easier to care for than systems that move water from one container to another.
STEPS TO SETTING UP A WICK SYSTEM
1.Install the tray in the grow space.
2.Find a support to raise the containers 4”-6” (10-15 cm) from the bottom of the tray. Wood blocks, pallets, and cement blocks all work well.
3.Measure distance from bottom of the tray through the container and back to the tray bottom. Cut the nylon rope. Seal ends.