by Ed Rosenthal
Fluorescents should be placed facing the wall so as to create a “wall” of lights. The plants are sandwiched between the wall and the bank of lights.
These plants were grown under a reflector that directed light to the walls as well as the floor. To utilize the light energy while keeping the plants from obstructing it, they were placed along the wall, behind netting.
The plants naturally spread out in three dimensions, but their depth or width can be controlled by training using stakes or plastic netting or even chicken wire placed on a frame. You can also just remove the branches that give the plant depth.
The netting is attached to the walls so there is a minimum 4" (10 cm) space between the netting and the wall. Twist ties are used to hold the branches to the frame.
EXAMPLE OF POOR GARDEN DESIGN
•The electrical system is haphazard and dangerous. The wiring is a series of extension cords, some of which are trailing to the floor. The wire jungle could be used as a net trap.
•The light is unprotected and can burst if it comes in contact with a drop of water.
•Without a reflector to direct the light much of it never gets to the garden, so it is wasted. The lamp is illuminating too large an area, about 60 sq ft (5.5 sq m).
•The fan is pointed directly on the light and blowing the hot air over the plant canopy.
•An old fashioned magnetic ballast powers the light; however, electronic ballasts use less power and would have saved about 8% in electrical costs.
•The ballast and tools are on a high shelf that makes them hard to get to.
•There is no indication of ventilation, heat exchange or CO2 enrichment.
SOIL
THE PURPOSE OF ROOTS
In earlier chapters most of the discussion was about the plant’s activities above the soil level. The plant’s roots, though hidden, are just as complex as the canopy.
It’s obvious that roots anchor a plant in place. The network of branches forms a tight relationship with the soil that firmly anchors the plant in the ground and holds it. Although the canopy may endure winds that tug and pull it, the roots provide stability to the stem, keeping it upright while allowing it to bend.
Roots supply the plant with water and nutrients. Using a complex series of bio-chemical processes, the roots gather nutrients and release sugars and enzymes into the environment.
Marijuana plants grow roots both vertically and horizontally. The horizontal roots can stretch out to a width equal to the plant’s canopy. This means that a plant that is 10' (3 m) wide has roots to match. The horizontal roots also grow down to a depth of between 9-18" (22-45 cm), depending on the soil’s moisture. The vertical roots can stretch down to 4' (1.2 m) or more in search of water; in moist soil, the vertical roots may be quite short.
ROOTS IN THE NATURAL SOIL ENVIRONMENT
Plants growing in a natural outdoor environment obtain their nutrients from the breakdown of complex organic chemicals into simpler water-soluble forms. The roots catch the chemicals using a combination of electrical charges and chemical manipulation. They are assisted by a thriving community of microorganisms that live in the rhizosphere, the area surrounding the root. These organisms are involved in a symbiotic relationship in which they help protect the root and supply it with minerals. In return the roots release sugars and other plant manufactures. This ecosystem is generally self-supporting.
NATURAL SOILS
Soils in the northern tier of North America and most of Europe form layers of decomposed plant material in two distinct patterns. Forest soils develop from the tree’s leaf drop. They form a layer by continually adding to the top layer. A typical soil of this kind has an undecomposed top layer. The contents are progressively more decomposed with the lower portions forming a fine compost. The depth of this layer varies by locale and natural environmental conditions as well as the forest’s history.
SOIL TIPS
Growing in soil has many advantages over any other method. It takes less labor and time to prepare the planting area. Adjusting the soil’s fertility with nutrients and amending it with additives such as compost, mulch, or fertilizer takes relatively little time and energy as compared with replacing a container’s soil.
Another advantage of soil is that it is easier to meet the plants’ needs as compared to using containers or hydroponic systems. Roots can stretch out and obtain water and nutrients from a larger area, and, as a result, they can support the needs of a larger plant.
There is no “perfect” soil for growing cannabis; different varieties each grow within a range of soil condition parameters. The soil must be well-drained, nutrient rich, and have a pH between 5.8-6.5.
Always test the soil to find out its requirements before preparing the soil for planting. The pH and fertility of soils vary so there are few generalizations that can be made about preparing them. Only after soil qualities and nutrient values are determined can the correct adjustments be made to optimize the soil’s fertility.
For marijuana plants, the soil should test high in the three macro-nutrients: nitrogen (N), phosphorous (P), and potassium (K) (see Nutrients). The most important quality of any soil is its texture, which is determined by the size of the soil particles. Marijuana prefers soil that drains well but also holds moderate to large quantities of water. Depending on the type of soil composition, add materials to improve the texture and nutrients.
When North America was colonized in the 16th century, earthworms were introduced that changed the soils in the eastern half of the continent. Earthworms pull semi-decomposed material down into their burrows, which have a depth of several feet. The large accumulation of duff that typified pre-colonial forests has largely disappeared. In its place, there is a smaller layer of decomposing compost soil. The mineral soil, which formed a distinct layer below the compost soil, is now laden with organic material and burrows that so it is more friable.
Grassland and prairie soils have a different history. The annual dieback of canopy growth deposits a small top layer that decomposes in the same way as in forest soils. However, most of the added organic material develops below the surface. It is fed by the dieback of annual plant roots. They compost in place, so the organic matter integrates with the mineral content of the soil, creating deep levels of nutrient-rich, composted material.
Warm soils such as those found in the warmer parts of North America and Europe contain much less organic matter and have fewer nutrients than northern soils because microorganisms, whose metabolic rates increase with the temperature, are more active, so they digest new organic matter almost as fast as it is deposited.
Gardeners can assess their soil using a soil-texture triangle that classifies the soil based on its percentages of sand, silt, and clay. Most gardens and fields that have been cultivated and have grown good crops fall within the acceptable categories of the soil triangle.
Moist warm tropical soils hold few nutrients. Nutrients in these areas are mainly held by living plants. As soon as vegetation dies, bacteria and other micro-life feast and render the nutrients water-soluble. They are absorbed into the soil and almost immediately taken up by the roots of higher living plants.
Underneath the layer of organic material in forest soils and the mixture of organic matter and minerals in grasslands lies the mineral soil, which contains little organic matter. The mineral portion of soils is usually composed of three main elements: sand, silt and clay. Each of them lends properties to the mix and each is needed in the mix in order to create a soil that promotes healthy growth.
The negatively charged molecules in clay cling together forming a barrier to water percolation. Clay has a negative electrical charge that binds minerals including Ca, magnesium, potassium and sodium. It releases them in exchange for weak hydrogen ions released by plant roots and microorganisms. Soils that are more than 30-40% clay are considered clay soils because the other ingredients are absorbed into the clay dough.
SOIL TYPE PARTICLE
Loams are composed of san
d, silt, and clay mixed with organic matter. As a result, the soil particles vary in size. This creates multiple paths for water to flow and also allows air pockets to remain, even when the soil is saturated.
Clay loams can be silty or sandy but are a little heavy and, in wet weather, can become saturated. Adding organic matter and sand increases porosity, although this may be an arduous undertaking.
Sandy soils leach water and nutrients. They need to be irrigated more often because they hold no water reserve. Sufficient amounts of compost, coir, peat moss, leaf clippings and planting mix add texture and increase its water- and nutrient-holding abilities.
Silty soils are composed of very small particles with a high surface-to-volume ratio that makes them chemically active. They hold nutrients in a buffer of charged particles, releasing them as roots draw them out using dilute acids. These soils hold water so well that heavy rains can result in anaerobic conditions, meaning the roots will be unable to get the oxygen they need. Sand and compost help increase soil porosity.
After assessing the soil’s pH, nutrients, and texture, the next step is usually tilling. There are two primary methods of preparing soil outdoors: either turning the whole area using a garden fork, rototiller, or tractor and plow or preparing discrete planting areas such as holes, or raised mounds or beds that hold a single plant or group of plants.
Tilling, or turning the soil over, breaks up compacted soil, and mixes in amendments such as compost and fertilizers, and making it easier for roots to penetrate.
Most of the time, soils need loosening to a depth of 10-15" (25-38 cm). However, soil with loose texture, sandy soils, and soils high in organic matter may have adequate aeration, porosity, and space for roots and may not have to be tilled at all.
Soil amendments and fertilizers to improve the nutrients are easily mixed into the soil when it is being prepared.
TEXTURE
Regardless of the particular composition of your soil, its texture is critically important to healthy plants. Texture refers to a soil’s density, particle size, and stickiness—all of which affect the soil’s ability to hold or drain water. Root health, and ultimately plant health, relies mainly on the soil’s drainage ability. If a pool of water develops after rain, the soil is saturated. There are no air pockets and the roots receive no oxygen; plants fail because root and stem rot attack roots weakened by the anaerobic conditions. Well-drained soil allows roots to be in contact with both water and air, the ideal condition for healthy growth.
Medium-textured soils—soils that drain well but can also hold an adequate amount of water—are best for cannabis. Loams, silts, and sands drain well and are usually loose enough to encourage healthy root development. Many clays and mucks are too compacted for lateral roots to penetrate, and when dry clay soils form hard crusts or clods, marijuana plants simply cannot thrive.
There are a few simple tests you should always perform before planting that will help you to check both the moisture-holding and drainage characteristics of your soil. For best results, test the soil when it is moist but not wet.
First, dig a hole 3' (0.9 m) deep so you can examine the soil’s profile; that is, the composition of its layers. You can use the method described in the box "Determining Soil Texture" to get a more accurate sense of the soil’s relative percentages of clay, sand, silt, and humus, but even a visual inspection should tell you what kind of soil you have. Soils that develop under trees or other overhanging plant cover have decaying plant matter at the top that decomposes into a layer of topsoil. The nutrients the plant needs to grow are found at the topsoil layer, though nutrients also leach to the next lower level.
Topsoil, which can be as shallow as an inch (2.5 cm) or several feet (a meter) deep, is usually the darkest of the layers. It is home to an abundance of life, including a variety of worms, bugs, and microorganisms such as yeasts, fungi, anachria and protozoa. If you can dig through the topsoil layer easily with your hands, its texture is right for healthy root growth.
By contrast, soil that has been covered primarily by grasses and annual plants has accumulated organic matter in a different way. Known as “prairie soils,” they may have a thin layer of topsoil near the surface, but the nutrient-rich area is deeper than the topsoil. The root layer of annual plants die off and decompose each year, leaving an organic component that provides nutrients, holds moisture, improves texture, and hosts beneficial organisms. This layer, while sometimes shallow, can reach a depth of 10' (3 m).
Whether you’ve got forest or prairie soil, you’ll find a layer of subsoil beneath the nutrient-rich upper layer. The subsoil can be composed of clay, sand, fine mineral particles, and small rocks. Sandy, rocky, and loamy subsoils provide excellent drainage without amending.
DETERMINING SOIL TEXTURE
Fill a quart jar two-thirds with water and add soil until the water nears the top. Screw on lid and shake thoroughly. Allow the soil to settle. The heaviest sand particles sink to the bottom and quickly become visible. It will take hours for the silt and clay particles to settle. The fine clay particles are so small that the molecular action of water will keep them in suspension indefinitely.
Below the subsoil, you may find clay or bedrock; both can create drainage problems, particularly if the area is in a spot with a high water table or where the soil tends to remain wet. If you are hitting clay or bedrock within three feet (0.9 m) of the soil surface, consider alternatives such as building raised beds or mounds to ensure proper drainage and adequate root penetration.
After you’ve done your visual inspection of the soil, you should use the squeeze test. Take a handful of soil from each layer and squeeze it tightly. Release it, and then poke the soil ball you’ve created with a finger. If it falls apart easily, the soil is either sandy or loamy. If the soil remains hard and stuck together, or if it feels sticky, you have quite a bit of clay or muck present and you need to amend it.
Testing soil for drainage is very simple. Fill the hole you’ve dug with water, wait one half-hour to allow the water to penetrate the surrounding soil, and then fill the hole again with water. If the moisture drains easily, the soil you are working with is sandy soil. If the water has still not drained through after 24 hours, the soil has very poor drainage.
TYPES OF SOIL
Each type of soil has its own unique characteristics that determine how it interacts with plants. Soils can be mainly classified as sands, clays, silts, loams, or mucks. Most soil is a combination of two or more of these. Sand granules, bits of clay, organic matter, and fine silty material can all be found in a random handful of soil.
SANDY SOILS
Sand is formed from ground or weathered rocks, including limestone, quartz, granite and shale. Sand doesn’t form bonds easily so little water is trapped. Sandy soils drain quickly and they don’t hold moisture and nutrients very well. Some sandy soils are particularly fertile, however, because they contain significant amounts (up to 2%) of organic matter. This matter also helps the soil hold water.
Sandy soils are rich in potassium (K), magnesium (Mg), and trace elements, but are often too low in phosphorous (P) and nitrogen (N). Nitrogen, the most soluble of the elements, is quickly leached from sandy soil. Yellow, pale, stunted or very thin plants growing in sandy soil usually indicate low nitrogen.
Sandy soils are easily prepared for cannabis cultivation. First, clear the ground cover from the soil. Next, treat it with humus, manure, chopped plant debris, chopped newspaper, real charcoal or other organic, nitrogen-containing fertilizer. Adding mineral soil (sub-soil) or used planting mix increases its water-holding capacity and fertility.
Sandy soil with some organic matter or loam that are supporting healthy plants doesn’t usually need to be turned or tilled because plant roots can penetrate easily. Hoe the planting row immediately before planting. Add nutrients using water-soluble fertilizers.
Water-holding pellets, made with polymers that swell to hold water and release it gradually as the soil dries, lengthen the time between waterin
gs.
Sandy soils are improved by spreading layers of uncomposted vegetative matter over the garden area. Nutrients gradually leach into the soil and the protective layer acts as a mulch to slow evaporation.
SILTS
Silts are composed of fine particles of organic matter combined with minerals such as quartz or other fine sands. Silty soils resemble a sort of mucky clay when wet, and look like dark sand or brittle clods when dry. Silts are the result of alluvial flooding, created by the deposits that remain after rivers and lakes flood. Alluvial silty soils are most commonly found in the Midwest, in valleys and along river plains. The Mississippi Delta, for example, is a very fertile alluvial plain.
If you have clay-loam or compacted soil you can use it for making raised beds. First, turn the soil in the whole area. Construct aisles by digging out pathways and adding soil from the aisles to the beds. As you fill the beds amend the clay-loam by mixing in organic soil amendments and sand. Build the bed 2' to 3' tall (60-90 cm).
Silts drain well, but they also hold moisture well. They are rich in most nutrients unless they were leached out by bad gardening techniques. They are simple to work with when damp and are regarded as some of the most fertile soils for planting cannabis. Gardens using silty soils must be irrigated frequently. Usually, they support very healthy and hearty plants because they contain an excellent supply of nitrogen.