Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

solution flows into the growing medium and is taken up by roots. The runoff nutrient solution is directed back to the reservoir as soon as it drains from the growing medium. Rockwool, gravel, coconut coir, and expanded clay are the most common growing mediums found in top-feed systems. Versatile top-feed systems can be used with individual containers or slabs in individual beds or lined up on tables.
    Top-feed systems come in many configurations. Systems with several gallons of growing medium are best for growing large plants that may require support. Small containers are perfect for smaller plants.
Top-Feed Buckets
    Self-contained top-feed buckets consist of a growing container nested inside a reservoir containing a pump. Individual buckets make culling out and replacing a sick plant quick and easy. Self-contained top-feed bucket systems are also perfect for growing large mother plants. The container can be moved anywhere easily. Some containers have a net pot suspended in the lid of a five-gallon (19 L) bucket/reservoir. The roots hang down into the reservoir. An air stone in the bottom of the reservoir aerates the nutrient solution. A separate pump cycles the irrigation to the container. Other self-contained top-feed buckets use a large growing container filled with expanded clay pellets. A pump constantly cycles nutrient solution in the system, aerating the solution and irrigating the plant. Roots grow down into the nutrient solution to form a mass on the bottom. Irrigation from the top circulates aerated nutrient solution and flushes out old oxygen-poor solution. Some systems contain a one-inch (3 cm) pipe to draw air directly down to the root zone. There are many different variations of this system, and they all work!

These top feed buckets filled with hydroclay are all set up and ready to be planted. More hydroclay will be added when clones are transplanted.

The grower plants three well-rooted cuttings in each container.
    Other top-feed bucket systems employ multiple buckets that are connected to a main reservoir. A flexible drain hose is attached near the bottom of the bucket/reservoir. The hose is connected to a drainage manifold that shuttles runoff nutrient solution back to a central reservoir.
    Each reservoir below the growing container holds an inch or two of water. It is important to regularly cycle irrigation in these gardens, so the solution in the bottom of the buckets does not stagnate.
    Top-feed buckets can also be lined up on a drainage table. Square containers make most efficient use of space. Plants are fed with irrigation tubing attached to a manifold. Once delivered, the nutrient solution flows and percolates through the growing medium. Roots take in the aerated nutrient solution before it drains onto the tray and back to the reservoir.

Containers are irrigated with spaghetti tubes attached to a manifold that runs between the rows. Excess nutrient solution drains out the bottom and is directed back to the reservoir via a drain tube.

This cutaway of a top-feed bucket system shows how roots dangle in a 100 percent humid environment before growing into the nutrient solution. Remember to screen the drain in the reservoir so roots do not block it.
    Individual containers in top-feed bucket systems are easy to arrange to fit into the allotted garden space. Plants can also be transplanted or removed from pots and cared for individually.
Top-Feed Slabs
    Top-feed slab systems are popular among small and large indoor and greenhouse growers. Rockwool or coco slabs covered in plastic serve as growing containers. The nutrient solution is delivered via spaghetti tubes from the top of the slab. An emitter attached to the spaghetti tube doses a specific measure of nutrient solution to each plant. The nutrient solution is aerated as it is applied, before being absorbed by the growing medium and draining back to the reservoir.
    A simple nutrient solution delivery manifold consists of emitters connected to spaghetti delivery tubes. The tubes are attached to a short manifold that is fed by a pump submerged in a reservoir.
    Emitters are designed to be anchored in growing medium and to emit a measured dose of nutrient solution.
    Some systems use individual trays to contain slabs. Nutrient solution is pumped from the reservoir and delivered to plants via spaghetti tubes attached to emitters. Individual trays are easy to configure for different sized gardens.
Tables of Slabs
    You can also set up a drainage table