DIY Organic Potting Mix's for Grass - Ace Spicoli

[acespicoli]

English version

Bread from Stones by Julius Hensel– Book Review

Bread from Stones “Our most optimistic expectations are no less than the realization of an old dream: ‘What will fertilizing with stone dust accomplish? It will turn stones into bread, make barren regions fruitful, and feed the hungry.’” --Ward Chesworth and coauthors, quoting Julius Hensel...

www.remineralize.org

Agrominerals - Wikipedia

en.wikipedia.org

Read the book Bread from Stones very interesting concepts

https://drive.google.com/file/d/1P7xV8QFoa79BObiV7ZDcZLhlz9JcvI-5/view?usp=sharing

A poster here in this thread had mentioned to add glacial rock dust once

Also greensand is already part of the fertilizer and river sand I have some clay sorbent im considering trying
theres always room improvement

will review the rock fertilizer recipes in the book as time goes on and leave results
Agrominerals very brilliant my PHD friend Thank you for sharing !

 

[acespicoli]

Pages in category "Soil physics"​

The following 60 pages are in this category, out of 60 total. This list may not reflect recent changes.

​

• Soil physics

B​

• Bioclogging
• Bound water
• Bulk density

C​

• Capacitance probe
• Capillary fringe

D​

• Darcy (unit)
• Darcy's law
• Disc permeameter
• Dispersion (geology)
• Drainage equation

E​

• Ecohydrology
• Epiphreatic zone
• Expansive clay

F​

• Field capacity
• Finite water-content vadose zone flow method
• Frequency domain sensor

G​

• Groundwater recharge

H​

• Horton overland flow
• Hydraulic conductivity
• Hydraulic redistribution
• Hydrus (software)

I​

• Infiltration (hydrology)
• Infiltrometer
• Integral energy

M​

• Macropore
• Mariotte's bottle
• Moisture equivalent

N​

• Neutron probe
• Nonlimiting water range

O​

• Optimum water content for tillage

P​

• Pedotransfer function
• Percolation test
• Permanent wilting point
• Permeability (materials science)
• Phreatic zone
• Porosity

R​

• Richards equation
• Routing (hydrology)
• Runoff curve number

S​

• SahysMod
• SaltMod
• Soil crust
• Soil gas
• Soil moisture sensor
• Soil moisture velocity equation
• Soil-plant-atmosphere continuum
• Sorptivity
• Specific storage
• Stress distribution in soil

T​

• TDR moisture sensor
• Tensiometer (soil science)
• Soil thermal properties
• Thixotropy
• Time-domain reflectometer

V​

• Vadose zone

W​

• Water content
• Water cycle
• Water potential
• Water retention curve

 

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Permanent wilting point (PWP) or wilting point (WP) is defined as the minimum amount of water in the soil that the plant requires not to wilt. If the soil water content decreases to this or any lower point a plant wilts and can no longer recover its turgidity when placed in a saturated atmosphere for 12 hours. The physical definition of the wilting point, symbolically expressed as θpwp or θwp, is said by convention as the water content at −1,500 kPa (−15 bar) of suction pressure, or negative hydraulic head.[1]

• Available water capacity
• Ecohydrology
• Field capacity
• Moisture equivalent
• Moisture stress
• Nonlimiting water range
• Soil plant atmosphere continuum
• Water retention curve

 

[PH donner]

Agrominerals - Wikipedia

en.wikipedia.org

Read the book Bread from Stones very interesting concepts
View attachment 19081307
https://drive.google.com/file/d/1P7xV8QFoa79BObiV7ZDcZLhlz9JcvI-5/view?usp=sharing

A poster here in this thread had mentioned to add glacial rock dust once

Also greensand is already part of the fertilizer and river sand I have some clay sorbent im considering trying
theres always room improvement

will review the rock fertilizer recipes in the book as time goes on and leave results
Agrominerals very brilliant my PHD friend Thank you for sharing !

Yes, I know that book.
There was a time when I spent many hours looking for this kind of information on the net.

I would like to point out that you can speed up the process that the plants can absorb it by adding 10/15% pure worm poop.

 

[acespicoli]

We call that EWC Earth Worm Castings here.
Did raise Red Wigglers also known as Eisenia fetida

Was a good point to add the living soil so to speak has organisms that are able to

dissolve minerals from rock

2.4 - Types of Weathering - Biological | Soil Genesis and Development, Lesson 2 - Processes of Weathering - passel

passel2.unl.edu

Many times we forget what we learn until we need to remember

 

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• Carbon cycle
• Nitrogen cycle

Ratio of carbon to nitrogen​

A conceptual view of C cycling and N cycling during organic matter decomposition.
The soil microbial population releases exoenzymes

(1), which depolymerize the dead organic matter
(2). The microbial decomposers assimilate the monomers
(3) and either mineralize these into inorganic compounds like carbon dioxide or ammonium
(4) or use the monomers for their biosynthetic needs. N mineralization leads to a loss of ammonium to the environment
(5), but this process is only relevant if the organic matter has a low C:N ratio. Ammonium from the environment can be immobilized if the dead organic matter has a high C:N ratio and thus provides insufficient N
(6). The high microbial N demand leads to a retention of N within the organic matter and thus to a decrease of the C:N ratio over the course of decomposition. [3]

Whether nitrogen mineralizes or immobilizes depends on the carbon-to-nitrogen ratio (C:N ratio) of the decomposing organic matter.[4] In general, organic matter contacting soil has too little nitrogen to support the biosynthetic needs of the decomposing soil microbial population.

If the C:N ratio of the decomposing organic matter is above circa 30:1 then the decomposing microbes may absorb nitrogen in mineral form as, e. g., ammonium or nitrates. This mineral nitrogen is said to be immobilized. This may reduce the concentration of inorganic nitrogen in the soil and thus the nitrogen is not available to plants.

As carbon dioxide is released during the generation of energy in decomposition, a process called "catabolism", the C:N ratio of the organic matter decreases.
When the C:N ratio is less than circa 25:1,
further decomposition causes mineralization by the simultaneous release of inorganic nitrogen as ammonium. When the decomposition of organic matter is complete, the mineralized nitrogen therefrom adds to that already present in the soil and therefore increases the total mineral nitrogen in the soil.

 

[acespicoli]

• Carbon cycle

 

[PH donner]

There was a time when Mearl consisted of algae and coral reefs, unfortunately this is no longer the case for environmental reasons. Sad but understandable. This was/is truly a wonderful addition. especially in areas with hard water.

 

[acespicoli]

There was a time when Mearl consisted of algae and coral reefs, unfortunately this is no longer the case for environmental reasons. Sad but understandable. This was/is truly a wonderful addition. especially in areas with hard water.

Maerl - Wikipedia

en.wikipedia.org

The sea is a meeting point of nutrients for sure, greensand

Greensand - Wikipedia

en.wikipedia.org

Glauconite - Wikipedia

en.wikipedia.org

Oyster shell

Kelp - Wikipedia

en.wikipedia.org

Kelp

Fish meal - Wikipedia

en.wikipedia.org

Phosphorite - Wikipedia

en.wikipedia.org

Langbeinite - Wikipedia

en.wikipedia.org

Our friend here Dank Frank and our host Gypsy also have a go in the yard and get some dirt method

 

[acespicoli]

Soil texture - Wikipedia

en.wikipedia.org

Soil horizon - Wikipedia

en.wikipedia.org

Aquifer - Wikipedia

en.wikipedia.org

Sub-irrigated planter - Wikipedia

en.wikipedia.org

 

[acespicoli]

please help - show me the best auto water!!! Do you know a better way, Do they work well ? Capillary Mat Systems

please help - show me the best auto water Some favorite hydro threads Hydro Showdown rdwc-grow-along snypes-guide-to-rdwc root volume rdwc been looking into automation (getting smarter or lazy 🤷‍♂️ ) peat based organic nute super soiless (organic-hydro???) Guide to Blumat-Regulated...

www.icmag.com

 

[acespicoli]

Dissolved Mineral Sources and Significance​

Home | NGWA / All About Groundwater / Groundwater Fundamentals

• Information on Earth’s Water
• Groundwater Facts
• Facts About Global Groundwater Usage
• Groundwater Use in the U.S.A.
• The Hydrologic Cycle
• Occurrence of Groundwater
• Forces Controlling Water in Rocks
• Unconfined or Water Table Aquifers
• Confined or Artesian Groundwater
• Springs
• Principles of Induced Infiltration and Artificial Recharge
• Evaluating the Hydrologic Properties of Water-Bearing Materials
• Unconformities and Groundwater Systems
• Relation of Salt Water to Fresh Water in Aquifers
• Dissolved Mineral Sources and Significance

The chemical character of groundwater is influenced by the minerals and gases reacting with the water in its relatively slow passage through the rocks and sediments of the Earth’s crust. Many variables cause extensive variation in the quality of groundwater, even in local areas. Generally, groundwater increases in mineral content as it moves along through the pores and fracture openings in rocks. This is why deeper, older waters can be highly mineralized. At some point, the water reaches an equilibrium or balance, which prevents it from dissolving additional substances.
About 50 properties are subject to determination, but only certain ones need be known to determine its usefulness. Dissolved minerals are reported in terms of several differing units of measurement. The most common practice is to report dissolved minerals in parts per million (ppm) by weight. One ppm is equivalent to the weight of one part of the dissolved mineral contained in one million parts by weight of the solution. Some agencies report analyses in units of milligrams per liter, which is equivalent to ppm. Hardness has been commonly expressed in grains per gallon. One grain per U.S. gallon equals 17.12 ppm.
The following characteristics of groundwater give it certain advantages over surface water.

1. Groundwater usually contains no suspended matter.
2. Groundwater, very rarely contains pathogenic bacteria; generally it contains microbes native to the formation, unless contaminated by human activity (Michael J. Schieders, Water Systems Engineering Inc., via personal communication.)
3. Groundwater is clear and colorless unless tainted with humic material.
4. The temperature of groundwater is relatively constant and is equivalent to, or greater than, the mean air temperature above the land surface. Temperatures can be altered by human influence.

The data presented is derived from work published by J.H. Criner, E.M. Cushing, and E.H. Boswell of the USGS (1961, Source and significance of dissolved mineral constituents and physical properties of natural waters, USGS Training Aid No. 1).

Corrosiveness​

Water that attacks metal is said to be corrosive. It frequently results in "red water" caused by solution of iron; however, not all red water is the result of corrosion. Water from some formations contains considerable iron in solution, which, on being exposed to the air, precipitates readily and gives a red-water effect. Acids and strong bases are capable of causing corrosion, and, together with an extreme pH, they support electrochemical processes that cause deterioration of water pipes, steam boilers, and water-heating equipment. Preventive measures involve control of these active agents or minimizing their effects and include maintaining proper pH stability in the treated water. Electrolysis control inside steel reservoirs and protective coating on metal surfaces also are used for protection against corrosion. Free carbon dioxide and other gases normally are removed by aeration and, if necessary, neutralized by the addition of either lime or soda ash.

In the photo at right, the red iron coloring and metals enrichment in this Colorado spring are caused by groundwater coming in contact with naturally occurring minerals present as a result of ancient volcanic activity in the area. Photo courtesy USGS.

Manganese​

Dissolved from some rocks and soils, and not so common as iron, manganese (chemical symbol Mn) has many of the same objectionable features as iron. The oxidized form of manganese causes dark brown or black stains. Large quantities of manganese are commonly associated with high iron content and acid water.

Calcium and magnesium​

Dissolved from practically all solids and rocks, but especially from limestone, dolomite, and gypsum, calcium (Ca) and magnesium (Mg) are found in large quantities in some brines. Magnesium is present in large quantities in sea water. It causes most of the hardness and scale-forming properties of water. Water low in calcium and magnesium is desired in electroplating, tanning, dyeing, and in textile manufacturing. Calcium and magnesium are the principal cause of the formation of scale in boilers, water heaters, and pipes, and to the objectionable curd in the presence of soap. These mineral constituents and hardness greatly affect the value of water for public and industrial uses.

Sodium and potassium​

Dissolved from practically all rocks and soils, sodium (Na) and potassium (K) are also found in ancient brines, sea water, some industrial brines, and sewage. Large amounts (500 ppm or more) in combination with chloride give a salty taste. High sodium content commonly limits use of water for irrigation. Sodium salts (50 ppm or more) may cause foaming in steam boilers. Compounds of sodium and potassium are abundant in nature and highly soluble in water. Some groundwater that contains moderate amounts of dissolved material may, in passing through sodium- and potassium-containing rock formations, undergo base exchange and become soft at greater depths.

Bicarbonate and carbonate​

Generated by the action of carbon dioxide in water on carbonate rocks such as limestone and dolomite, bicarbonate (HCO3-) and carbonate (CO3-2) produce an alkaline environment. Bicarbonates of calcium and magnesium decompose in steam boilers and hot-water facilities to form scale and release corrosive carbonic acid gas. In combination with calcium and magnesium, they cause carbonate hardness. Bicarbonate is of little significance in public supplies except in large amounts, where taste is affected or where the alkalinity affects the corrosiveness of the water.

Temperature​

The Earth’s temperature or chemical reaction affects the usefulness of water for many purposes. Most users desire water of uniformly low temperature. In general, temperatures of shallow groundwater show some seasonal fluctuation whereas temperatures of groundwater from moderate depths remain near or slightly above the mean annual air temperature of the area. In deep wells, the water temperature generally increases 1 °F for each 60 feet to 100 feet of depth.

Sulfate​

Sulfates (SO4-2)are dissolved from rocks containing gypsum, iron sulfides, and other sulfur compounds. Commonly present in mine water and in some industrial wastes, large amounts have a laxative effect on some people and, in combination with other ions, give a bitter taste. Sulfate in water containing calcium forms a hard scale in steam boilers.

Chloride​

Chlorides (Cl-) are dissolved from rocks and soils. Present in sewage and found in large amounts in ancient brines, sea water, and industrial brines, large quantities increase the corrosiveness of water and, in combination with sodium, give a "salty" taste. The chlorides of calcium, magnesium, sodium, and potassium are readily soluble. Drainage from salt springs and sewage, oil fields, and other industrial wastes may add large amounts of chloride to streams and groundwater reservoirs. Small quantities of chloride have little effect on the use of water. Sodium chloride imparts a salty taste, which may be detectable when the chloride exceeds 100 ppm, although in some water, 500 ppm may not be noticeable. Chlorides in high concentrations present a health hazard to children and other young mammals.

Aluminum​

Aluminum (Al) is derived from bauxite and other clays. Although present in many rocks, aluminum is not highly soluble and precipitates readily. There is no evidence that it affects use of water for most purposes. Acid water (low pH) often contains greater amounts of aluminum. Such water is troublesome for boiler feed because of the formation of scale.

Silica​

Dissolved from practically all rocks and soils, silica (SiO2) is generally found in small amounts from 1 ppm to 30 ppm. Higher concentrations generally occur in highly alkaline water. Silicas form a hard scale in pipes and boilers. Carried over in steam of high-pressure boilers, silicas form damaging deposits on the delicately balanced blades of steam turbines. Silica also inhibits the deterioration of zeolite-type water softeners, but does not affect water for domestic purposes. Groundwater generally contains more silica than surface water.

Iron​

Extremely common, iron (Fe) is dissolved from practically all rocks and soils. Water having a low pH tends to be corrosive and may dissolve iron in objectionable quantities from pipe, pumps, and other equipment. More than 1 ppm to 2 ppm of soluble iron in surface water generally indicates the presence of acid wastes from mine drainage or other sources. More than about 0.3 ppm stains laundry and utensils reddish-brown. Objectionable for food processing, beverages, dyeing, bleaching, ice manufacturing, brewing, and other processes, moderately large quantities cause unpleasant taste and favor the growth of iron bacteria under slight oxidizing conditions and typical groundwater temperatures. On exposure to air, iron in groundwater is readily oxidized and forms a reddish-brown precipitate. Iron can be removed by oxidation, sedimentation, and fine filtration, or by precipitation during removal of hardness by ion exchange (not a recommended practice).

Nitrate​

Sources of nitrate (NO3-) are decaying organic matter, legume plants, sewage, nitrate fertilizers, and nitrates in soil. Nitrate encourages growth of algae and other organisms that cause undesirable tastes and odors. Concentrations much greater than the local average may suggest pollution. Nitrate in water may indicate sewage or other organic matter. In amounts less than 5 ppm, nitrate has no effect on the value of water for ordinary uses.

Dissolved solids​

Chiefly, "dissolved solids" is the total quality of mineral constituents dissolved from rocks and soils, including any organic matter and some water of crystallization. Water containing more than 1,000 ppm of dissolved solids is unsuitable for many purposes. The amount and character of dissolved solids depend on the solubility and type of rocks with which the water has been in contact. The taste of the water often is affected by the amount of dissolved solids.

Hardness as magnesium and calcium carbonates​

In most water, nearly all the hardness is due to calcium and magnesium carbonates. All of the metallic cations other than the alkali metals deposit soap curd on bathtubs. Hard water forms scale in boilers, water heaters, and pipes. Hardness equivalent to the bicarbonate and carbonate is called carbonate or "temporary" hardness because it can be removed by boiling. Any hardness in excess of this is called noncarbonate or "permanent" hardness. Noncarbonate hardness is caused by the combination of calcium and magnesium with sulfate, chloride, and nitrate. Scale caused by carbonate hardness usually is porous and easily removed, but that caused by noncarbonate hardness is hard and difficult to remove. Hardness is usually recognized in water by the increased quantity of soap or detergent required to make a permanent lather. As hardness increases, soap consumption rises sharply, and an objectionable curd is formed. In the development of a water supply, hardness is one of the most important factors to be considered. In general, water of hardness up to 60 ppm is considered soft; 61 to 120 ppm moderately hard, 121 to 180 ppm hard, and more than 180 ppm very hard.

Turbidity​

Water turbidity is attributable to suspended matter such as clay, silt, fine fragments of organic matter, and similar material. It shows up as a cloudy effect in water and for this reason alone is objectionable in domestic and many industrial water supplies. Filtered water is free from noticeable turbidity. Unfiltered supplies, including those that contain enough iron for appreciable precipitation on exposure to air, may show turbidity. In surface water supplies, turbidity is usually a more variable quantity than dissolved solids.
Photo courtesy NCDFR.

Color​

Color refers to the appearance of water that is free of suspended matter. It results almost entirely from extraction of coloring matter and decaying organic materials such as roots and leaves in bodies of surface water or in the ground. Natural color of 10 units or less usually goes unnoticed and even in larger amounts is harmless in drinking water. Color is objectionable in the use of water for many industrial purposes, however. It may be removed from water by coagulation, sedimentation, and activated carbon filtration.

Fluoride​

Dissolved in small to minute quantities from most rocks and soils such as fluorspar and cryolite, fluoride (Fl) in drinking water has been shown to reduce the incidence of tooth decay when the water is consumed during a child’s period of tooth enamel calcification. However, it may cause mottling of the teeth depending on the concentration of fluoride, the age of the child, the amount of drinking water consumed, and the susceptibility of the individual.

Reactions with formation minerals​

A small number of minerals comprise nearly the entire mass of sandstone aquifers. The average sandstone, as determined by F.W. Clarke (1924, The data of geochemistry, fifth ed., USGS Bulletin 770), consists of 66.8 percent silica (mostly quartz), 11.5 percent feldspars, 11.1 percent carbonate minerals, 6.6 percent micas and clays, 1.8 percent iron oxides, and 2.2 percent other minerals. Limestone and dolomite aquifers are primarily calcium carbonate and calcium magnesium carbonate, respectively, but impure ones may contain as much as 50 percent noncarbonate constituents such as silica and clay minerals.
Quartz, the main constituent of sandstones, is the least reactive of the common minerals and, for all practical purposes, can be considered nonreactive except in highly alkaline solutions (Roedder, E., 1959, Physics and Chemistry of the Earth 3). Clays have been demonstrated to react with highly basic or highly acidic solutions.
Clay minerals are common constituents of sedimentary rocks. Roedder (1959) stated that sandstones containing less than 0.1 percent clay minerals might not exist anywhere in the United States, except possibly in small deposits of exceedingly pure glass sand. Clay minerals are known to reduce the permeability of sandstone to water as compared with its permeability to air (Johnston, N., and C.M. Beeson, 1945, Water permeability of reservoir sands, Petroleum Development and Technology, in Transactions of the American Institute of Mining and Metallurgical Engineers 160: 43-55; Baptist, O.C., and S.A. Sweeney, 1955, Effect of clays on the permeability of reservoir sands to various saline water, Bureau of Mines Report of Investigations 5180; Land, C.S., and A. Baptist, 1965, Effect of hydration of montmorillonite on the permeability of water-sensitive reservoir rocks, Journal of Petroleum Technology October). The degree of permeability reduction to water as compared with air is termed the water sensitivity of a sandstone by Baptist and Sweeney.

The above information is excerpted in large part from Chapter 23 of the 1999 NGWA Press publication, Ground Water Hydrology for Water Well Contractors.​

Groundwater | Dissolved mineral sources and significance

www.ngwa.org

 

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Forces Controlling Water in Rocks​

Home | NGWA / All About Groundwater / Groundwater Fundamentals

• Information on Earth’s Water
• Groundwater Facts
• Facts About Global Groundwater Usage
• Groundwater Use in the U.S.A.
• The Hydrologic Cycle
• Occurrence of Groundwater
• Forces Controlling Water in Rocks
• Unconfined or Water Table Aquifers
• Confined or Artesian Groundwater
• Springs
• Principles of Induced Infiltration and Artificial Recharge
• Evaluating the Hydrologic Properties of Water-Bearing Materials
• Unconformities and Groundwater Systems
• Relation of Salt Water to Fresh Water in Aquifers
• Dissolved Mineral Sources and Significance

The two most important forces controlling water movement in rock are gravity and molecular attraction. Gravity causes water to infiltrate until it reaches impermeable zones where it is diverted laterally. Gravity generates the flow of springs, rivers, and wells. If the pores in rocks and sediments are connected, gravity allows the water to move slowly through them. However, the smaller the opening, the harder it is for gravity to cause water movement. The second force, molecular attraction, slows the flow of water through small pores. Water is attracted to the surface of every particle with which it comes in contact. The force results from the attraction of the molecules of two substances for each other.

Molecular attraction of water in rocks​

The attraction between water and soil or rock particles is termed adhesion. It is effective only over short distances. Thus, only a thin film of water is locked to the outside of each grain resisting the flow downward in response to gravity. It is this adhesion that helps hold water in soil for plants. If gravity were the only force involved, all water would drain through the soil to some depth. In fine-grained sediments such as silt and clay, the aggregate surface area which can attract water molecules is very great. Fine-grained materials hold more water over a longer period of time than the same volume of coarse-grained materials such as sand or gravel.

Surface tension and capillarity​

The attraction of water molecules for each other is termed cohesion. It can be demonstrated by immersing a pencil in water and noting the drop that remains at the base of the pencil, seemingly held there by the water above it. This attraction is due to the surface tension characteristic of water, caused by cohesion. Water will also rise in a small tube if it is immersed. This phenomenon is called capillary action or capillarity. The smaller the tube, the higher the water will rise. In The Occurrence of Ground Water in the U.S. with a Discussion of Principles, USGS Water-Supply Paper 489 (1923), Oscar E. Meinzer states the reason for this attraction of the water for the walls of the tube as follows: "The water in a capillary tube is held up not only by the attraction of the walls of the tube for the water but by this attraction acting through the cohesion of the water, whereby the influence of the attraction of the water was extended far beyond the range of molecular forces." Capillary action is important in rocks and sediments because pores immediately above the saturated zone are filled with capillary water. The more fine-grained the sediment or rock, the higher the water is pulled. The diameter of the pore opening and the degree of connection with the saturated zone is very important. So much water is drawn into the pores above the water table that this zone is given a special term, the capillary fringe.

Permeability of rocks​

Permeability is the capacity of a rock to transmit water under pressure. If no pressure exists, a static equilibrium is present and there is no tendency for water to move. This condition is very rare in nature. Most water can be thought to be in the dynamic state or moving in response to a pressure gradient.
Meinzer defines permeability as follows: "The permeability of a rock is measured by the rate at which it will transmit water through a given cross section under a given difference of pressure per unit of distance." In a sequence of sedimentary rock with varying permeability, it commonly can be shown that horizontal permeability or permeability that is parallel to the bedding of rocks such as sandstone and conglomerate is greater than permeability at right angles to bedding. This is because some beds in the sequence have such low permeability that vertical infiltration is slow whereas lateral permeability in units below confining beds is good.
No rocks near the surface of the earth are impermeable if enough pressure is applied in forcing the water through the natural openings in the rock. However, the forces generated by nature are insufficient in some cases to produce detectable permeability and rocks with such characteristics are said to be relatively impermeable. Examples of such rocks are found in shales that contain clays that swell on wetting and thus close off natural openings that may exist when the rock is dry. On the other hand, coarse, clean gravel contains such large openings that it readily transmits water. Ordinarily, such deposits function as the best aquifers where they can be easily recharged. Dirty or clay-rich gravels have much less permeability because the fine silt and clay between the larger particles effectively slow down or block completely the flow of water through some of the pores between the sand grains.

Coefficient of permeability​

The coefficient of permeability (P) used by the USGS may be expressed as the number of gallons of water a day, at 60 °F, that is conducted laterally through each square foot of water-bearing material (measured at right angles to the direction of flow), under a hydraulic gradient of 1 foot per foot. It has the units of gallons per day per square foot (gpd per sq. ft.).
For analyzing field tests involving flow through the entire thickness of aquifers, it is generally more convenient to use the coefficient of transmissivity (T) of C.V. Theis (1935, The relation between lowering of the piezometric surface and rate and duration of discharge of a well using groundwater storage, Transactions of the American Geophysical Union 16, 519-524). Theis expressed as "T = coefficient of transmissiblity of aquifer, in gallons a day, through each 1-foot strip extending the height of the aquifer, under a unit gradient—this is the average coefficient of permeability (Meinzer) multiplied by the thickness of the aquifer." It is expressed in gallons per day per foot (gpd per ft.). Both definitions are based upon Darcy's law.*

Darcy's law​

Darcy’s law states that the rate of movement of water through porous media is proportional to the hydraulic gradient:

q = k × dh/dl​

in which q = velocity of movement; k = constant of proportionality, which is the hydraulic conductivity; and dh/dl = hydraulic gradient, expressed as a change in head (dh) over a given change in flow length (dl).
For review, hydraulic gradient is the change in static head per unit of distance in a given direction, usually the direction of maximum decrease. Hydraulic gradient may be expressed in ft. per ft. or cm, per meter, etc., in the same way slope may be written.
*Groundwater hydrology began as a quantitative science when Henry Philibert Gaspard Darcy (1803-1858), a French hydraulic engineer, published a report on the water supply of Dijon, France. Darcy's law is a foundation stone for several fields of study including groundwater hydrology, soil physics, and petroleum engineering.

The above information is excerpted in large part from Chapter 13 of the 1999 NGWA Press publication, Ground Water Hydrology for Water Well Contractors.​

Groundwater | Forces controlling water in rocks

www.ngwa.org

 

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Equilibrium constant - Wikipedia

en.wikipedia.org

Hydrolysis - Wikipedia

en.wikipedia.org

Capillary Mats

Even the most strong and powerful tree begins as a fragile sprout coming out of a tiny seed. Nurturing that sprout or clone when it's young requires much more attention than when it's older and in a larger container. In general, the larger the container, the less frequently it needs irrigation...

sustainablevillage.com

Bulk Materials

Better Ways To Water with Blumat Watering Systems.

sustainablevillage.com

 

[acespicoli]

O) Organic surface layer: Plant litter layer—the upper part is often relatively undecomposed, but the lower part may be strongly humified. A) Surface soil: Layer of mineral soil with most organic matter accumulation and soil life. Additionally, due to weathering, oxides (mainly iron oxides) and clay minerals are formed and accumulated. It has a pronounced soil structure. But in some soils, clay minerals, iron, aluminum, organic compounds, and other constituents are soluble and move downwards. When this eluviation is pronounced, a lighter coloured E subsurface soil horizon is apparent at the base of the A horizon. The A horizon may also be the result of a combination of soil bioturbation and surface processes that winnow fine particles from biologically mounded topsoil. In this case, the A horizon is regarded as a "biomantle". B) Subsoil: This layer normally has less organic matter than the A horizon, so its colour is mainly derived from iron oxides. Iron oxides and clay minerals accumulate as a result of weathering. In soil, where substances move down from the topsoil, this is the layer where they accumulate. The process of accumulation of clay minerals, iron, aluminum, and organic compounds, is referred to as illuviation. The B horizon has generally a soil structure. C) Substratum: Layer of non-indurated poorly weathered or unweathered rocks. This layer may accumulate more soluble compounds like CaCO3. Soils formed in situ from non-indurated material exhibit similarities to this C layer. R) Bedrock: R horizons denote the layer of partially weathered or unweathered bedrock at the base of the soil profile. Unlike the above layers, R horizons largely comprise continuous masses (as opposed to boulders) of hard rock that cannot be excavated by hand. Soils formed in situ from bedrock will exhibit strong similarities to this bedrock layer.

Horizons and layers according to the World Reference Base for Soil Resources​

[edit]
The designations are found in Chapter 10 of the World Reference Base for Soil Resources Manual, 4th edition (2022).[2] The chapter starts with some general definitions:

The fine earth comprises the soil constituents ≤ 2 mm. The whole soil comprises fine earth, coarse fragments, artefacts, cemented parts, and dead plant residues of any size.

A litter layer is a loose layer that contains > 90% (by volume, related to the fine earth plus all dead plant residues) recognizable dead plant tissues (e.g. undecomposed leaves). Dead plant material still connected to living plants (e.g. dead parts of Sphagnum mosses) is not regarded to form part of a litter layer. The soil surface (0 cm) is by convention the surface of the soil after removing, if present, the litter layer and, if present, below a layer of living plants (e.g. living mosses). The mineral soil surface is the upper limit of the uppermost layer consisting of mineral material.

A soil layer is a zone in the soil, approximately parallel to the soil surface, with properties different from layers above and/or below it. If at least one of these properties is the result of soil-forming processes, the layer is called a soil horizon. In the following, the term layer is used to indicate the possibility that soil-forming processes did not occur.

The following layers are distinguished (see Chapter 3.3 of the WRB Manual):

• Organic layers consist of organic material: Have ≥ 20% organic carbon, not consisting of artefacts (related to the fine earth plus the dead plant residues of any length and a diameter ≤ 5 mm) and do not form part of a litter layer.
• Organotechnic layers consist of organotechnic material: Have ≥ 35% (by volume, related to the whole soil) artefacts containing ≥ 20% organic carbon; and < 20% organic carbon, not consisting of artefacts (related to the fine earth plus the dead plant residues of any length and a diameter ≤ 5 mm).
• Mineral layers are all other layers.

The designation consists of a capital letter (master symbol), which in most cases is followed by one or more lowercase letters (suffixes).

Master symbols​

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H: Organic or organotechnic layer, not forming part of a litter layer; water saturation > 30 consecutive days in most years or drained; generally regarded as peat layer or organic limnic layer.

O: Organic horizon or organotechnic layer, not forming part of a litter layer; water saturation ≤ 30 consecutive days in most years and not drained; generally regarded as non-peat and non-limnic horizon.

A: Mineral horizon at the mineral soil surface or buried; contains organic matter that has at least partly been modified in-situ; soil structure and/or structural elements created by cultivation in ≥ 50% (by volume, related to the fine earth), i.e. rock structure, if present, in < 50% (by volume).

E: Mineral horizon; has lost by downward movement within the soil (vertically or laterally) one or more of the following: Fe, Al, and/or Mn species; clay minerals; organic matter.

B: Mineral horizon that has (at least originally) formed below an A or E horizon; rock structure, if present, in < 50% (by volume, related to the fine earth); one or more of the following processes of soil formation:

• formation of soil aggregate structure
• formation of clay minerals and/or oxides
• accumulation by illuviation processes of one or more of the following: Fe, Al, and/or Mn species; clay minerals; organic matter; silica; carbonates; gypsum
• removal of carbonates or gypsum.

Nota bene: B horizons may show other accumulations as well.

C: Mineral layer; unconsolidated (can be cut with a spade when moist), or consolidated and more fractured than the R layer; no soil formation, or soil formation that does not meet the criteria of the A, E, and B horizon.

R: Consolidated rock; air-dry or drier specimens, when placed in water, will not slake within 24 hours; fractures, if present, occupy < 10% (by volume, related to the whole soil); not resulting from the cementation of a soil horizon.

I: ≥ 75% ice (by volume, related to the whole soil), permanent, below an H, O, A, E, B or C layer.

W: Permanent water above the soil surface or between layers, may be seasonally frozen

Soil horizon - Wikipedia

en.wikipedia.org

​

Base saturation​

Base saturation expresses the percentage of potential CEC occupied by the cations Ca2+, Mg2+, K+ or Na+.[1][4] These are traditionally termed "base cations" because they are non-acidic, although they are not bases in the usual chemical sense.[1] Base saturation provides an index of soil weathering[4] and reflects the availability of exchangeable cationic nutrients to plants.[1]

Anion-exchange capacity​

Positive charges of soil minerals can retain anions by the same principle as cation exchange. The surfaces of kaolinite, allophane and iron and aluminium oxides often carry positive charges.[1] In most soils the cation-exchange capacity is much greater than the anion-exchange capacity, but the opposite can occur in highly weathered soils,[1] such as ferralsols (oxisols).

 

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Rhizosphere - Wikipedia

en.wikipedia.org

Types of Roots​

Beyond just knowing what roots are, and do, you should also know the varied types of roots that exist. The most three common root types include -

1. Tap Root - A tap root references the large main base of the root that grows directly down into the soil.
2. Fibrous Root - Completely opposite of a tap root, fibrous roots are thinner branches that stem off of root tissue and grow into the medium.
3. Adventitious Root - Adventitious roots can sprout from any part of the plant, like the stem, and grow towards the medium.

Root - Wikipedia

en.wikipedia.org

A Complete guide to cannabis roots​

By:OG Wells

A common saying amongst growers is, healthy roots equal happy plants. Considering the roots serve as the base to successful growing plants. Without a healthy root system, your cannabis plant might not reach its full potential. So, ensuring a healthy environment for your roots to thrive is key to quality crops. That’s why we’ve put together your complete guide to cannabis roots, and how to provide optimal care.
CONTENTS

What do roots do?​

First thing’s first - let’s better understand the answer to the question, what do roots do? Cannabis roots are similar to the body’s vital organs, like the heart or brain that keep systems functioning, healthily. Roots act as the plant’s main control panel that intakes what the plant needs through the grow medium. Their primary function is absorbing water, nutrients and oxygen, and then delivering them properly to the plant. Hence, their importance to successful growth. Being the base of the plant, healthy roots are also necessary to stabilize or anchor the plant into the medium you’re growing in.

Types of Roots​

Beyond just knowing what roots are, and do, you should also know the varied types of roots that exist. The most three common root types include -

1. Tap Root - A tap root references the large main base of the root that grows directly down into the soil.
2. Fibrous Root - Completely opposite of a tap root, fibrous roots are thinner branches that stem off of root tissue and grow into the medium.
3. Adventitious Root - Adventitious roots can sprout from any part of the plant, like the stem, and grow towards the medium.

As for structure, the root’s main base typically begins growing down vertically into the soil or medium, and then branch into secondary roots. This secondary branch of roots is another heart-related reference, often called horizontal ‘capillaries’. Meaning the end shape of a healthy root system is usually similar to a pyramid.

How do roots develop?​

Roots do most of their developing in the vegetative stage of growth. They grow to their fullest potential in veg, and then begin to branch secondary roots once the plant has reached its flowering stage. The root capillaries are primarily responsible for absorbing nutrients to travel through the system, and back to the plant. Because roots grow in search of water, it’s important to use a medium or soil that enhances their ability to grow. Soils that are too compact can hinder secondary roots outreach. While soils that are over saturated can stunt growth altogether.

The signs of healthy roots​

When transplanting your plants from veg to flower, or into bigger pots - you’ll be able to get a first-hand glimpse into the root systems. So what are healthy roots supposed to look like? The signs of healthy roots include a milky white colouring, and should be odourless, too. If you’re growing in pots, you should be able to see the roots growing throughout the medium. In direct contrast to the roots circling around the edge of the container.

Keeping roots in good health​

Overall, there’s a few simple factors that when maintained, roots can remain in good health. Again, healthy roots produce high-quality plants making the following components that much more important to pay attention to.

Oxygen​

Plants receive oxygen through the roots, which is required for creating what’s known as the ATP molecule (adenosine triphosphate). This chemical is essential to successful growth, considering it’s the transporter of energy to the plant. Without a healthy root system, your plant might not get enough oxygen circulating which can cause a slow, starving death.
To improve oxygen intake for your plant, the following tips can help -

• Using smart pots or fabric pots.
• Adding perlite, vermiculite, or peat moss to your soil for an airy consistency.
• Using compost or organic soils with a blend of beneficial fungi, bacteria, insects, and microbes.

Temperature​

Just as important as oxygen for healthy roots is maintaining an ideal temperature, too. Cannabis roots are typically the happiest around 75℉ (24 ℃) where they can respire and grow properly. To regulate the temperature of your roots in soil-based systems, you can do any of the following-

• Promote air circulation with an air outtake and intake system, and fans near the base of your plants.
• Place thermometers throughout your grow set-up, and monitor temperatures regularly.
• Outdoors, cover the top layer of soil with hay or mulch to insulate the roots temperature.

In hydroponics, water should be kept between 66℉ - 77℉ (19℃ -25℃) for healthy roots. In this range, oxygen levels are at their highest which also promotes optimal nutrient uptake. Tips to regulating temperatures in hydroponic systems include -

• Installing a chiller system.
• Add ice to your reservoir as needed.
• Paint your container white, which reflects light and heat for cooling.

Water​

As we already mentioned, water is crucial to healthy root growth since roots extend in search of good ol’ H2O. So making sure you’re giving your roots the adequate amount, without overwatering is essential for cannabis plants. For soil environments, you’ll want to increase the amount of water slowly over time without over-doing it. It’s also beneficial to make sure you water all around the root especially towards the outer edge of the pot. In hydroponics, it’s all about the levels of water you submerge the roots in. You’ll want to maintain a fine line of keeping the roots wet to avoid drying out, but with enough air for respiration.

Nutrients​

Nutrients are just as beneficial for healthy root growth as they are for the boost in growth for plants. Phosphorus and potassium are the most vital to roots. These two nutrients promote the growth of new roots while also extending the existing roots, too. Nitrogen is also helpful for boosting levels of phosphorus, overall. Prepping your soil with these nutrients beforehand is ideal, by mixing in any of the following -

• Bone meal
• Rock phosphate
• Wood ashes
• Kelp
• Greensand

For hydroponics systems, using phosphorus and potassium rich fertilizers from the start can help promote healthy root growth. Or, use nutrients rich in vitamin b1, indole-3-butyric acid, or 1-Naphthylacetic acid which are additional root strengthening boosters.

Root issues to address​

When growing cannabis, it can be hard to decipher what signs or issues are what. Especially if they’re root issues that you can’t check or monitor, easily. We’ll make the issues simple with a breakdown of how to spot root issue symptoms, and what to do when they appear.

Overwatering & Under watering ​

A common mistake by beginner growers is overwatering or under watering. But fortunately it’s a mistake that shows itself quickly, and is easy to fix quickly, too. You’ll know your plant is getting too much or too little water, with the drooping or wilting of its leaves. When this occurs - check your soil. If it’s dry, you’re under watering. If it’s wet over a period of days, you’re overwatering. The solution? Simply change your watering cycle and amounts.
It’s best to let the soil completely dry out before re-watering. Do a weight check on your pots by lifting them before you water next, and make sure they’re light before water. If you’ve overwatered, let the pot completely dry out and use less water the first time you water again.

Nutrient Burn​

In cannabis, there can be too much of a good thing. Like nutrients, and the burn that can occur when you use an excessive amount. Overdoing nutrients can damage the health of roots which stunts the growth of your plant, and can decrease your final yields. So keep an eye out for upward facing fan leaves, or leaves with yellow brownish tips which are a telltale sign of nutrient burns. One factor that can affect nutrient uptake is pH balance, which can be addressed in a few ways.
First, reduce the amount of nutrients while you investigate the issue. Then, conduct a pH and EC check to decipher what is the cause of the burn. Flushing your plants with correct pH water for at least a week, is also recommended. Once they’re flushed, ensure you learn your lesson and reduce the amount of nutrients you use moving forward.

Root Rot​

With a name like root rot, you know it’s going to cause an issue in healthy growth for your plant. Meaning it’s important to avoid root rot before it occurs, especially since the signs can be harder to detect. Root rot occurs when bad fungi’s and bacteria build-up near the root system. This can occur from poor draining pots, and overwatering. The build up over time causes sickly, rotting roots.
The symptoms of root rot are similar to other common issues, like drooping, wilting, and yellowing leaves. But luckily, your sense of smell can help. Root rot will often emit a ‘rotten’ scent which you can sniff for, if you’re suspicious. Other than that, looking at the roots is the last resort which is obviously easier in a hydroponics system. If your roots are brown, and slimy then you’ve got a case of root rot.
To salvage your plants, immediately transplant into fresh, well-draining soil that’s chock-full of beneficial bacteria and fungi. Because of the shock, and obvious health issues you’ll want to ensure you monitor carefully and frequently from there. In hydroponics, you’ll want to completely clean and sanitize your entire system and add a bacterial agent to the fresh water. Before replacing your plants, gently washing the roots is also ideal.

Root Bound​

Bound roots often occur when using too small of a pot or container. The roots have no room to grow properly, so they begin circling, and ‘binding’ together. The entanglement of roots affects nutrient uptake, and will eventually halt growth of the plant. Again, without being able to see the roots - how will you tell if they’re bound? Here’s the biggest signs to look for

• Signs of nutrient deficiencies, like yellowing leaves.
• Soil that’s drying out quickly.
• Plant tipping or leaning.
• Growth slowing down dramatically.

Avoiding root bound is much easier than fixing it, so always be sure to transplant your plant into bigger pots as it grows. Or, transfer the plant to its final sized container earlier than usual. Checking your pot’s drainage holes is a good way to monitor the growth of cannabis roots in general, and when to identify the time to transplant. If you see the roots through these holes, move the plant to a bigger pot. If you come across a root bound plant, before switching pots you’ll want to loosen the roots first. To do so, shake off the soil from the roots and prune them slightly with sterilized trimmers.

Fungus Gnats​

Fungus gnats are the easiest root issue to identify, since you’ll see the flying bugs near the base of the plant. They’re also an issue you’ll want to treat quickly, since their larvae in wet soil feed off the root system overall damaging its health. If you want to keep a good eye on root issues before seeing the signs of them, you can periodically check your soil for fungus gnat eggs using a loupe if necessary for magnification. Not surprisingly, dropping or wilting leaves are also a sign of fungus gnat damage.
Once you’ve confirmed you have gnats, you’ll want to use sticky fly traps near the base of the plant. Because fungus gnats thrive in wet environments, hold off on watering and let your soil dry out, at the same time. To address the larvae, applying a mix of 1 part hydrogen peroxide to 4 parts water to the soil will kill what’s left behind. After that, and moving forward, cover your soil with perlite or sand as a barrier to bugs infiltrating the soil.

Healthy Roots for Happy High-Quality Plants​

Roots may be out of sight, but they should be far from out of mind. A healthy root system is the basis for happy, high-quality plants, and we all know what that means - maximized yields. With that in mind, use these tips and techniques to promote healthy root growth, and to avoid the common issues that can occur.

 

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Anions and cations​

Hydrogen atom (center) contains a single proton and a single electron. Removal of the electron gives a cation (left), whereas the addition of an electron gives an anion (right). The hydrogen anion, with its loosely held two-electron cloud, has a larger radius than the neutral atom, which in turn is much larger than the bare proton of the cation. Hydrogen forms the only charge-+1 cation that has no electrons, but even cations that (unlike hydrogen) retain one or more electrons are still smaller than the neutral atoms or molecules from which they are derived.
Anion (−) and cation (+) indicate the net electric charge on an ion. An ion that has more electrons than protons, giving it a net negative charge, is named an anion, and a minus indication "Anion (−)" indicates the negative charge. With a cation it is just the opposite: it has fewer electrons than protons, giving it a net positive charge, hence the indication "Cation (+)".

Since the electric charge on a proton is equal in magnitude to the charge on an electron, the net electric charge on an ion is equal to the number of protons in the ion minus the number of electrons.

An anion (−) (/ˈænˌaɪ.ən/ ANN-eye-ən, from the Greek word ἄνω (ánō), meaning "up"[13]) is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively charged and protons are positively charged).[14]

A cation (+) (/ˈkætˌaɪ.ən/ KAT-eye-ən, from the Greek word κάτω (kátō), meaning "down"[15]) is an ion with fewer electrons than protons, giving it a positive charge.[16]

There are additional names used for ions with multiple charges. For example, an ion with a −2 charge is known as a dianion and an ion with a +2 charge is known as a dication. A zwitterion is a neutral molecule with positive and negative charges at different locations within that molecule.[17]

Cations and anions are measured by their ionic radius and they differ in relative size: "Cations are small, most of them less than 10−10 m (10−8 cm) in radius. But most anions are large, as is the most common Earth anion, oxygen. From this fact it is apparent that most of the space of a crystal is occupied by the anion and that the cations fit into the spaces between them."[18]

The terms anion and cation (for ions that respectively travel to the anode and cathode during electrolysis) were introduced by Michael Faraday in 1834 following his consultation with William Whewell.

Natural occurrences​

Ions are ubiquitous in nature and are responsible for diverse phenomena from the luminescence of the Sun to the existence of the Earth's ionosphere. Atoms in their ionic state may have a different color from neutral atoms, and thus light absorption by metal ions gives the color of gemstones. In both inorganic and organic chemistry (including biochemistry), the interaction of water and ions is often relevant for understanding properties of systems; an example of their importance is in the breakdown of adenosine triphosphate (ATP), which provides the energy for many reactions in biological systems.

Ion - Wikipedia

en.wikipedia.org

 

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Plastics Topics – Static electricity and plastics 3 Triboelectric series Human skin Loses electrons.

Becomes positively charged. + ve.
Asbestos
Rabbit fur
Cellulose
Acetate
Glass
Human hair
PA (Nylon)
Wool
Lead
Silk
Aluminium
Paper
Cotton
Steel

Gains electrons.

Becomes negatively charged. -ve.
Wood
Hard rubber
Copper Silver Brass PS Polyacrylonitrile fibres (e.g., Orlon™) PMMA (Acrylic) Vinylidene Chloride Copolymers (e.g., SARAN™) PUR (Polyurethane) PE (Polyethylene) PP (Polypropylene) PVC PCTFE Silicon PTFE Silicone Rubber The Triboelectric series

https://tangram.co.uk/wp-content/uploads/Plastics-Topics-Static-electricity-and-plastics.pdf

 

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Soil Chemical Properties​

Overview​

Title Image "Nutrient bioavailability with regards to soil pH" is copyrighted and used with permission from the American Society of Agronomy, Crop Science Society of America and Soil Science Society of America.

Did you have an idea for improving this content? We’d love your input.

Introduction​

Learning Objectives​

• Explain the chemical properties of the soil and soil/medium pH on nutrient availability.
• Explain how soil pH effect nutrient availability for plants.
• Describe the process of cation exchange.
• Explain how negatively charged mineral ions are more likely to be leached.

​

Key Terms​

acidic soil - soil with a pH level less than 7
alkaline soil - soil with a pH level greater than 7
anion - negative ion that is formed by an atom gaining one or more electrons
cation - positive ion that is formed by an atom losing one or more electrons
cation exchange capacity - the measure of the total amount of exchangeable positive ions that a soil can hold
ion - atom or chemical group that does not contain equal numbers of protons and electrons
leach - the act of chemicals or minerals being drained away from soil by water
soil electrical conductivity - measure of the amount of salts in soil
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3_Soil-Chemical-Properties​

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Soil pH​

Even though most plants are autotrophs and can generate their own sugars from carbon dioxide and water, they still require certain ions and minerals from the soil. An ion is an atom or chemical that does not contain equal numbers of protons and electrons. Ions are either anions or cations. An anion is a negative ion that is formed by an atom gaining one or more electrons, and a cation is a positive ion that is formed by an atom losing one or more electrons. By definition, “pH” is a measure of the active hydrogen ion (H+) concentration. It is an indication of the acidity or alkalinity of a soil, and is also known as “soil reaction.” The pH scale ranges from 0 to 14, with values below 7.0 being considered acidic and values above 7.0 alkaline. A pH value of 7 is considered neutral, where H+ and OH- are equal, both at a concentration of 10-7 moles/liter. A pH of 4.0 is ten times more acidic than a pH of 5.0. Some minor elements (e.g., iron) and most heavy metals are more soluble at lower pH. This makes pH management important in controlling movement of heavy metals (and potential groundwater contamination) in soil.
The most important effect of pH in the soil is on ion solubility, which in turn affects microbial and plant growth. A pH range of 6.0 to 6.8 is ideal for most crops because it coincides with optimum solubility of the most important plant nutrients. Not all ions are equally available in soil water; their availability depends on the properties of the soil. Clay is negatively charged; thus, any positive ions (cations) present in clay-rich soils will remain tightly bound to the clay particles. This tight association with clay particles prevents the cations from being washed away by heavy rains, but it also prevents the cations from being easily absorbed by plant root hairs. In contrast, anions are easily dissolved in soil water and thus readily accessible to plant root hairs; however, they are also very easily leached or washed away by rainwater. In this way, the presence of clay particles creates a trade-off for plants: they prevent leaching of cations from the soil by rainwater, but they also prevent absorption of the cations by the plant. In acid soils, hydrogen and aluminum are the dominant exchangeable cations. The latter is soluble under acidic conditions, and its reactivity with water (hydrolysis) produces hydrogen ions. Calcium and magnesium are basic cations; as their amounts increase, the relative amount of acidic cations will decrease. Let's take phosphorous as an example (Figure 4.2.1) If soils are too acidic, phosphorus reacts with iron and aluminum. That makes it unavailable to plants. But if soils are too alkaline, phosphorus reacts with calcium and also becomes inaccessible.

Figure 4.3.1 Nutrient bioavailability with regards to soil pH.Image used with permission from the American Society of Agronomy, Crop Science Society of America and Soil Science Society of America

Factors that affect soil pH include parent material, vegetation, and climate. Some rocks and sediments produce soils that are more acidic than others: quartz-rich sandstone is acidic; limestone is alkaline. Some types of vegetation, particularly conifers, produce organic acids, which can contribute to lower soil pH values. In humid areas such as the eastern US, soils tend to become more acidic over time because rainfall washes away basic cations and replaces them with hydrogen. Addition of certain fertilizers to soil can also produce hydrogen ions. Liming the soil adds calcium, which replaces exchangeable and solution H+ and raises soil pH. Lime requirement, or the amount of liming material needed to raise the soil pH to a certain level, increases with CEC. To decrease the soil pH, sulfur can be added, which produces sulfuric acid.
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3.2 Soil pH​

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Nutrient Availability​

How do plants acquire micronutrients from the soil? This process is mediated by root hairs, which are extensions of the root epidermal tissue that increase the surface area of the root, greatly contributing to the absorption of water and minerals. Root hairs absorb ions that are dissolved in the water in soil.

How do plants overcome these issues?​

The cell in the root utilizes active transport (use of energy to transport a substrate against the concentration gradient) to move mineral ions into the root cells. Proton pumps or ATPases, use ATP as an energy source to pump protons out of the cells and into the soils leading to an increase in the concentration of protons (H+) thus lowering the pH or acidifying the microscopic area of soil surrounding the root hair and generating electrochemical gradient (difference in concentration and electrical charge of species across a membrane). These pumps are located on the plasma membrane and are found in the cells of root hair, cortex, and endodermal layer. Based on apoplastic, symplastic or transmembrane route (unit 2, lesson 3 Xylem transport) the mineral ions are actively loaded into the root vascular system.
Protons pumped in the soil may participate in exchange of cations on the surface of the soil particles or accompany an anion into a plant cell or generate the gradient for specific ion to be transported across the plasma membrane into the cell. To facilitate the transport of cations and anions into the plant cells proton pumps work in conjugation with either antiporters, symporters, or uniporters (Figure 4.3.2). Antiporters transport different ions or molecules across the plasma membrane in opposite directions while symporters transport ions or molecules in the same direction. Uniporters transport one specific ion or molecule across the plasma membrane.

Figure: 4.3.2. Schematic diagram of a uniporter, symporter (symporter), and antiporter (Lupask, Public domain, via Wikimedia Commons)

Electrochemical gradient leads to two outcomes:

1. Protons bind to the negatively charged clay particles, replacing the cations from the clay in a process called cation exchange. The cations then diffuse down their electrochemical gradient into the root hairs. High concentration of negatively charged organic anions within the cells also favor the transport of cations into the cells.
2. The high concentration of protons in the soil creates a strong electrochemical gradient that favors transport of protons back into the root hairs. Plants use co-transport of protons via symporters down their concentration gradient as the energy source to move anions against their electrical gradient into the root hairs. (The soil environment is highly positively charged, so it is unfavorable for anions to leave the soil, but highly favorable for protons to leave the soil).

As of now, proton pumps are considered central to the mineral ion transport across the root plasma membrane. However, studies of the involvement of redox chains, and OH- efflux transporters during anion transport are also underway. Redox chains located on the plasma membrane are utilized by many plants, such as corn and oats, for anion absorption. Redox chains pump electrons out of the cells, thus creating an electrical gradient for anion uptake. More research is in progress to complete the characterization of proteins in the redox chains and understand their mechanisms. OH-efflux transporters are unique in enhancing the anion absorption by excreting negatively charged hydroxyl ion (OH-) outside of the root cell. These transporters need further research to increase our understanding of anion absorption in plants.
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3.3 Nutrient Availability​

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Cation Exchange Capacity​

The cation exchange capacity of a soil is a measurement of the magnitude of the negative charge per unit weight of soil or the amount of cations a particular sample of soil can hold in an exchangeable form. The greater the clay and organic matter content, the greater the cation exchange capacity should be; although, different types of clay minerals and organic matter can vary in cation exchange capacity. soil electrical conductivity is a measure of the amount of salt in soil. Because salts move with water; low areas, depressions, or other wet areas where water accumulates tend to be higher in electrical conductivity than surrounding higher-lying, better drained areas. Clay soils dominated by clay minerals that have a high cation-exchange capacity have higher electrical conductivity than clay soils dominated by clay minerals that have a low cation exchange capacity. Soils with restrictive layers, such as claypans, typically have higher electrical conductivity because salts cannot be leached from the root zone and accumulate on the surface.
Cation exchange is an important mechanism in soils for retaining and supplying plant nutrients, as well as for adsorbing contaminants. For example, it plays an important role in wastewater treatment in soils. Sandy soils with a low cation exchange capacity are generally unsuited for septic systems since they have little adsorptive ability and there is potential for groundwater.
Due to the influence of pH and clay on ion retention, as well as other parameters, the composition and texture of soil greatly influences the ability of roots to penetrate the soil, as well as the availability of water, nutrients, and oxygen:

Composition	Water availability	Nutrient availability	Oxygen availability	Root penetration ability
Sand	Low: water drains out	Low: poor capacity for cation exchange; anions leach out	High: many air-containing spaces	High: large particles do not pack tightly
Clay	High: water clings to charged surface of clay particles	High: large capacity for cation exchange; anions remain in solution	Low: few air-containing spaces	Low: small particles pack tightly
Organic matter	High: water clings to charged surface of clay particles	High: ready source of nutrients, large capacity for cation exchange; anions remain in solution	High: many air-containing spaces	High: large particles do not pack tightly

While plants have ready access to carbon (carbon dioxide) and water (except in dry climates or during drought), they must extract minerals and ions from the soil. Often nitrogen is most limiting for plant growth; while it comprises approximately 80% of the atmosphere, gaseous nitrogen is chemically stable and not biologically available to plants. Many plants have evolved mutualistic relationships with microorganisms, such as specific species of bacteria and fungi, to enhance their ability to acquire nitrogen and other nutrients from the soil. This relationship improves the nutrition of both the plant and the microbe.
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3.4 Cation Exchange Capacity​

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Dig Deeper​

Cation Exchange Video
Mineral Absorption Video:

Attributions​

"Adhesion and Cohesion of Water" by the United States Department of Agriculture Natural Resources Conservation Service is in the Public Domain.
Haynes, R.J. Active ion uptake and maintenance of cation-anion balance: A critical examination of their role in regulating rhizosphere pH. Plant Soil 126, 247–264 (1990). https://doi.org/10.1007/BF00012828
"Nutrient Acquisition by Plants" by Georgia Tech Biological Sciences is licensed under CC BY-NC-SA 3.0.
"Nutrient Bioavailability" graphic used with permission from the American Society of Agronomy, Crop Science Society of America and Soil Science Society of America.
OpenStax Biology 2e by Mary Ann Clark, Matthew Douglas, and Jung Choi is licensed under CC BY 4.0.
"Soil Electrical Conductivity" by the United States Department of Agriculture Natural Resources Conservation Service is in the Public Domain.
"Soil Physical and Chemical Properties" by the United States Department of Agriculture Natural Resources Conservation Service is in the Public Domain.

 

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The information described above is organized in table form below: