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Viewed from Centre of Eternity 615.552.5747
-+- The Merry Pranksters from Menlo Park -+-
10.1990.01.01.15
Marijuana Grower's Handbook - part 15 of 33
by pH Imbalance
"pH and Water"
from
Marijuana Grower's Handbook
[Indoor/Greenhouse Edition]
Ed Rosenthal
The pH is the measure of acid-alkalinity balance of a solution. It is
measured on a scale of 0-14, with 0 being the most acid, 7 being neutral,
and 14 being most alkaline. [pH:In case you're wondering, I'm a total 0!]
Most nutrients the plants use are soluble only in a limited range of acidity,
between about 6 to about 7.5, neutral. Should the water become too acidic or
alkaline, the nutrients dissolved in the water become too acidic or alkaline,
the nutrients dissolved in the water precipitate and become unavailable to the
plants. When the nutrients are locked up, plant growth is slowed. Typically,
a plant growing in an environment with a low pH will be very small, often
growing only a few inches in several months. Plants growing in a high pH
environment will look pale and sickly and also have stunted growth.
All water has a pH which can be measured using aquarium or garden pH
chemical reagent test kits or a pH meter. All of these items are available
at local stores and are easy to use. Water is pH-adjusted after nutrients
are added, since nutrients affect the pH.
Once the water is tested it should be adjusted if it does not fall within
the pH range of 6 to 7. Ideally the range should be about 6.2-6.8.
Hydroponic supply companies sell measured adjusters which are very
convenient and highly recommended. The water-nutrient solution can be
adjusted using common household chemicals. Water which is too acidic can be
neutralized using bicarbonate of soda, wood ash, or by using a solution of
lime in the medium.
Water which is too alkaline can be adjusted using nitric acid, sulfuric
acid, citric acid (Vitamin C) or vinegar. The water is adjusted using small
increments of chemicals. Once a standard measure of how much chemical is
needed to adjust the water, the process becomes fast and easy to do.
Plants affect the pH of the water solution as they remove various
nutrients which they use. Microbes growing in the medium also change the
pH. For this reason growers check and adjust the pH periodically, about
once every two weeks.
The pH of water out of the tap may change with the season so it is a good
idea to test it periodically.
Some gardeners let tap water sit for a day so that the chlorine
evaporates. They believe that chlorine is harmful to plants.
The pH of the planting medium affects the pH of the liquid in solution.
Medium should be adjusted so that it tests between 6.2-6.8. This is done
before the containers are filled so that the medium could be adjusted in
bulk. Approximately 1-2 lbs. of dolomitic limestone raises the pH of 100
gallons (4.5-9 grams per gallon) of soil 1 point. Gypsum can be used to
lower the pH of soil or medium. Both limestone and gypmsum have limited
solubility.
There are many forms of limestone which have various effectiveness
depending on their chemistry. Each has a rating on the package.
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