This information was obtained from the internet:
By Matt Rize
"Citric Acid and Cannabis Horticulture:
Citric acid is a weak organic acid, it is a tricarboxylic acid, C6H8O7 . It is a natural preservative and used to make food taste sour, like 'sour patch kids' and soda. In biochemistry, citric acid is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of virtually all living things.
This post is all about citric acid.. The Cannabis growers of the world use citric acid to lower water pH for container gardens. Cannabis grown in soil-less organics prefers a soil(less) solution around 6.3 pH, and hydro is lower. A neutral water pH is 7.0, and my tap water is usually around 8.0 pH. So WHY do we use citric acid, and not the countless other acids, to lower our pH? The reasons are solid, let's investigate.
We need to begin by defining the important soil science terms that relate to soil-less organics.
Soil:
Layer of unconsolidated material found at the Earth's surface that has been influenced by the soil forming factors: climate, relief, parent material, time, and organisms. Soil normally consists of weathered mineral particles, dead and living organic matter, air space, and the soil solution.
Soil Solution:
Aqueous liquid found within a soil. This liquid normally contains ions released from mineral particles, organic matter or plant roots and leaves.
Soil Colloids:
Very small organic and inorganic particles found in a soil. Inorganic colloids are often clay particles. Soil colloids carry a negative electrical charge and are the primary sites for cation exchange. Soil colloids hold large quantities of elements and compounds which are used by plants for nutrition.
Ions:
An atom, molecule or compound that carries either a positive (cation) or negative (anion) electrical charge.
Cation Exchange Capacity:
The capacity of a soil to exchange cations with the soil solution. Often used as a measure of potential soil fertility.
Okay, now we have learned: what soil is, what a soil solution is, and how soil colloids play a key role in plant nutrition by holding elements and compounds.
BACK TO CITRIC ACID...
Citric acid is valuable as an additive in Cannabis horticulture for these reasons:
A. Citric acid (C6H8O7 ) bonds to Phosphorus anions (P-), making them soluble in the rhizosphere and soil solution.
Phosphorus anions (P-) are not easily mobile in the soil solution. The soil solution is a thin layer of water and microbes surrounding particles in media, soil-less and soil. Phosphorus anions bond with media particles, other elements, and organic matter. When bound P- is made insoluble and unavailable to plants roots. Citric acid bonds with P- and this keeps this needed nutrient in a form available to plant roots.
There are cations in the soil(less) solution. There are also cations in the cation exchange sites of media particles. Together these cations are held in equilibrium, but things can go wrong, especially in an unbalanced soil-less media. Managing this equilibrium is our goal.
By adding citric acid to our water and/or nutrient solution we release (solubilize) the Phosphorus anions. The roots can then use the ions in the soil solution and rhizosphere. The ability of roots to uptake all nutrients is directly dependent on pH of the solution, and the solubility of those nutrients. Citric acid (aka citrate) increases the bio-availability of Phosphorus anions (P-) present in the media.
B. Citric acid plays a role in the Krebs Cycle
Look for a post on this subject soon!
Look for an upcoming post on ROOT EXUDATES! Roots secrete all sorts of weak acids to free up N/P/K, Ca, Fe, and possibly other elements.
Root Exudates: (substances secreted by the roots).
Roots exude large amounts of citric acid into the grow media, this keeps the P- soluble in the rhizosphere and soil solution. This citric acid, and other acid root exudates , mineralize P- from organic matter like soft rock phosphate or bat guano.
Some good reading can be found below. Definitions were adapted from: PhysicalGeography.net.
1. Bioavailability of soil inorganic P in the rhizosphere as affected by root-induced chemical changes: a review
Philippe Hinsinger
Plant and Soil 237: 173–195, 2001.
2. Effects of root exudates on nutrient availability in the rhizosphere
A. Gransee
Plant Nutrition Developments in Plant and Soil Sciences, 2002, Volume 92, Symposium 9, 626-627,
3. Carbonic Acid Decomposition
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
By Matt Rize
"Citric Acid and Cannabis Horticulture:
Citric acid is a weak organic acid, it is a tricarboxylic acid, C6H8O7 . It is a natural preservative and used to make food taste sour, like 'sour patch kids' and soda. In biochemistry, citric acid is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of virtually all living things.
This post is all about citric acid.. The Cannabis growers of the world use citric acid to lower water pH for container gardens. Cannabis grown in soil-less organics prefers a soil(less) solution around 6.3 pH, and hydro is lower. A neutral water pH is 7.0, and my tap water is usually around 8.0 pH. So WHY do we use citric acid, and not the countless other acids, to lower our pH? The reasons are solid, let's investigate.
We need to begin by defining the important soil science terms that relate to soil-less organics.
Soil:
Layer of unconsolidated material found at the Earth's surface that has been influenced by the soil forming factors: climate, relief, parent material, time, and organisms. Soil normally consists of weathered mineral particles, dead and living organic matter, air space, and the soil solution.
Soil Solution:
Aqueous liquid found within a soil. This liquid normally contains ions released from mineral particles, organic matter or plant roots and leaves.
Soil Colloids:
Very small organic and inorganic particles found in a soil. Inorganic colloids are often clay particles. Soil colloids carry a negative electrical charge and are the primary sites for cation exchange. Soil colloids hold large quantities of elements and compounds which are used by plants for nutrition.
Ions:
An atom, molecule or compound that carries either a positive (cation) or negative (anion) electrical charge.
Cation Exchange Capacity:
The capacity of a soil to exchange cations with the soil solution. Often used as a measure of potential soil fertility.
Okay, now we have learned: what soil is, what a soil solution is, and how soil colloids play a key role in plant nutrition by holding elements and compounds.
BACK TO CITRIC ACID...
Citric acid is valuable as an additive in Cannabis horticulture for these reasons:
A. Citric acid (C6H8O7 ) bonds to Phosphorus anions (P-), making them soluble in the rhizosphere and soil solution.
Phosphorus anions (P-) are not easily mobile in the soil solution. The soil solution is a thin layer of water and microbes surrounding particles in media, soil-less and soil. Phosphorus anions bond with media particles, other elements, and organic matter. When bound P- is made insoluble and unavailable to plants roots. Citric acid bonds with P- and this keeps this needed nutrient in a form available to plant roots.
There are cations in the soil(less) solution. There are also cations in the cation exchange sites of media particles. Together these cations are held in equilibrium, but things can go wrong, especially in an unbalanced soil-less media. Managing this equilibrium is our goal.
By adding citric acid to our water and/or nutrient solution we release (solubilize) the Phosphorus anions. The roots can then use the ions in the soil solution and rhizosphere. The ability of roots to uptake all nutrients is directly dependent on pH of the solution, and the solubility of those nutrients. Citric acid (aka citrate) increases the bio-availability of Phosphorus anions (P-) present in the media.
B. Citric acid plays a role in the Krebs Cycle
Look for a post on this subject soon!
Look for an upcoming post on ROOT EXUDATES! Roots secrete all sorts of weak acids to free up N/P/K, Ca, Fe, and possibly other elements.
Root Exudates: (substances secreted by the roots).
Roots exude large amounts of citric acid into the grow media, this keeps the P- soluble in the rhizosphere and soil solution. This citric acid, and other acid root exudates , mineralize P- from organic matter like soft rock phosphate or bat guano.
Some good reading can be found below. Definitions were adapted from: PhysicalGeography.net.
1. Bioavailability of soil inorganic P in the rhizosphere as affected by root-induced chemical changes: a review
Philippe Hinsinger
Plant and Soil 237: 173–195, 2001.
2. Effects of root exudates on nutrient availability in the rhizosphere
A. Gransee
Plant Nutrition Developments in Plant and Soil Sciences, 2002, Volume 92, Symposium 9, 626-627,
3. Carbonic Acid Decomposition
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
