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Viewed from Centre of Eternity 615.552.5747
-+- The Merry Pranksters from Menlo Park -+-
10.1990.01.01.10
Marijuana Grower's Handbook - part 10 of 33
by pH Imbalance
"Growing in the Ground"
from
Marijuana Grower's Handbook
[Indoor/Greenhouse Edition]
Ed Rosenthal
Some growers have the opportunity to grow plants directly in the ground.
Many greenhouses are built directly over the earth. Growing directly in the
soil has many advantages over container growing. A considerable amount of
labor may be eliminated because there is no need to prepare labor-intensive
containers with expensive medium. Another advantage is that the plants'
needs are met more easily.
Before using any greenhouse soil, it is necessary to test it. The pH and
fertility of soils vary so much that there are few generalizations that can
be made about them.
The most important quality of any soil is its texture. Soils which drain
well usually are composed of particles of varying size. This creates paths
for water to flow and also allows airs pockets to remain even when the soil
is saturated.
Soils composed of very fine particles, such as mucks and clay, do not
drain well. Few air particles are trapped in these soils when they are
saturated. When this happens, the roots are unable to obtain oxygen and
they weaken when they are attacked by anaerobic bacteria. These soils
should be adjusted with sand and organic matter which help give the medium
some porosity. Materials suitable for this include sand, compost, composted
manure, as well as perlite, lava, gravel, sphagnum moss, styrofoam particles
and foam particles.
Low lying areas may have a very high water table so that the soils remain
saturated most of the time. One way to deal with this problem is to create
a series of mounds or raised beds so that the roots are in ground at higher
level than the floor level.
Once soil nutrient values are determined, adjustments can be made in the
soil's fertility. For marijuana, the soil should test high in total
Nitrogen, and the medium should test high in Phosphorous and Potassium.
This is covered in subsequent files.
Growers use several methods to prepare the soil. Some prefer to till the
whole area using either a fork, a roto-tiller or a small tractor and plow.
The marijuana plant grows both vertical and horizontal roots. The
horizontal roots grow from the surface to a depth of 9-18 inches depending
on the soil's moisture. They grow closer to the surface of moist soils.
The vertical root can stretch down several feet in search of water. In
moist soils, the vertical roots may be short, even stunted.
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. Most soils should be dug to a depth of 6-9 inches.
The tighter the soil's texture, the deeper it should be filled.
If the soil is compacted, it is dug to a depth of two feet. This can be
done by plowing and moving the soil in alternate rows and then plowing the
newly uncovered soil. Soil texture adjustors such as gypsum are added to
the bottom layer of the soil as well as the top layer, but soil amendments
such as fertilizers or compst are added only to the top layer, where most of
the plant's roots are. Then the soil is moved back into the troughs and the
alternate rows are prepared the same way.
A variation of this technique is the raised bed. First, the whole area
is turned, and then aisles are constructed by digging out the pathways and
adding the material to the beds. With the addition of organic soil
amendments, the total depth of prepared soil may stretch down 18 inches.
Some growers use planting holes rather than tilling the soil. A hole
ranging between 1 and 3 feet wide and 1.5 and 3 feet deep is dug at each
space where there is to be a plant. The digging can be facilitated using a
post hole digger, electric shovel, or even a small backhoe or power hole
digger. Once the hole is dug the soil is adjusted with amendments or even
replaced with a mix.
No matter how the soil is prepared, the groundwater level and the
permeability of the lower layers is of utmost importance. Areas with high
water tables, or underlying clay or hardpan will not drain well. In either
case the harden should be grown in raised beds which allow drainage through
the aisles and out of the growing area, rather than relying on downward
movement through soil layers.
Soils in used greenhouses may be quite imbalanced even if the plants were
growing in containers. The soil may have a buildup of mutrient salts,
either from runoff or direct application, and pesticides and herbicides may
be present. In soils with high water tables, the nutrients and chemicals
have nowhere to go, so they dissolve and spread out horizontally as well as
vertically, contaminating the soil in surrounding areas.
Excess salts can be flushed from the soil by flooding the area with water
and letting it drain to the water table. In areas with high water tables,
flushing is much more difficult. Trenches are dug around the perimeter of
the garden which is then flooded with nutrient-free water. As the water
drains into the trenches, it is removed with a pump and transported to
another location.
Pesticides and herbicides may be much mroe difficult to remove. Soils
contaminated with significant amounts of residues may be unsuitable for use
with material to be ingested or inhaled. Instead, the garden should be
grown in containers using nonindigenous materials.
Usually plants are sexed before they are planted into the ground. If the
soil showed adequate nutrient values no fertilizer or side dressing will be
required for several months.
Several growers have used ingenious techniqures to provide their gardens
with earthy environments. One grower in Oregon chopped through the concrete
floor of his garage to make planting holes. The concrete had been poured
over sub-soil so he dug out the holes and replaced the sub-soil with a
mixture of composted manure, vermiculite, perlite, worm castings, and other
organic ingredients. He has been using the holes for several years. After
several crops, he redigs the holes and adds new ingredients to the mix.
A grower in Philadelphia lived in a house with a backyard which was
cemented over. He constructed a raised bed over the concrete using railroad
ties and filled it with a rich topsoil and composted manure mixture, then
built his greenhouse over that. The growing bed is about 15 inches deep and
the grower reports incredible growth rates.