In The Beginning
Thus the heavens and the earth were completed, and all their hosts. 2 By the seventh day God completed His work which He had done, and He rested on the seventh day from all His work which He had done. 3 Then God blessed the seventh day and sanctified it, because in it He rested from all His work which God had created [a]and made.
4 [b]This is the account of the heavens and the earth when they were created, in the day that the Lord God made earth and heaven. 5 Now no shrub of the field was yet in the earth, and no plant of the field had yet sprouted, for the Lord God had not sent rain upon the earth, and there was no man to [c]cultivate the ground. 6 But a [d]mist used to rise from the earth and water the whole [e]surface of the ground. 7 Then the Lord God formed man of dust from the ground, and breathed into his nostrils the breath of life; and man became a living [f]being. 8 The Lord God planted a garden toward the east, in Eden; and there He placed the man whom He had formed. 9 Out of the ground the Lord God caused to grow every tree that is pleasing to the sight and good for food; the tree of life also in the midst of the garden, and the tree of the knowledge of good and evil.
…18“Both thorns and thistles it shall grow for you; And you will eat the plants of the field; 19By the sweat of your face You will eat bread, Till you return to the ground, Because from it you were taken; For you are dust, And to dust you shall return.”
But now, O LORD, thou art our father; we are the clay, and thou our potter; and we all are the work of thy hand.
Pretty Dramatic huh! First I would like to start out by explaining a key to how this will be laid out. All quotes and professional text will be italicised. The explaining I do in between the text will be written in this aqua color. Pertainent information I feel important to the message in the professional text will also be highlighted in aqua color. The purpose of this article is not to try and persuade anyone that akadama is organic, which it isn’t, but to try and show some of the confusing and often times contradictory information that circulates around akadama. Internet discussion forums are ablaze with people looking for substitutes at any price, substitutes cheaper than the real thing, and substitutes in their own locality. In many parts of our USA people use tyrface as an alternative to akadama, thinking that adding a clay component along with lava, pumice will give them the magic combonation we seek. Sorry, it don’t work that way.
In the above text taken directly from the King james Bible, we can read of inferences to dust from the ground, building a human from dust of the ground, and a correlation between man and clay and the creator making man from clay. Why is this important? It is important because we have an acient text written so that everyone can understand it and see the reference to man and clay. So important in fact that one might think that clay, or soil if you will, contains the building block of life. From a biblical point of view it does. Later on we will discover how these building block might be used in other ways as well.
Lets read on:
Study suggests life began with clay, echoing Bible creation story
Published November 06, 2013
A new study suggests clay may have been the birthplace of life on Earth.
Cornell University researchers found that clay may have served as the first breeding ground for the complex biochemicals that make life possible, a finding that may reverberate with anyone familiar with the Biblical creation story.
“We propose that in early geological history, clay hydrogel provided a confinement function for biomolecules and biochemical reactions,” said Dan Luo, professor of biological and environmental engineering and a member of the Kavli Institute at Cornell for Nanoscale Science, according to Science Daily .
The clay absorbs liquids like a sponge and acts as the perfect place for chemicals to react with one another to form proteins, DNA and eventually living cells.
According to the Old Testament, God made the first man Adam from earth or clay. Adam comes from the Hebrew word adamah, which means earth. The Quaran, Greek mythology and other creation stories also say God molded man from clay.
Scientists found that the clay hydrogel could have protected the chemical processes until the membrane that surrounds living cells fully developed.
The study cites further evidence, nothing that geological history shows the first appearance of clay to be at the same time biomolecules began to form into cell-like structures.
How the biological machines evolved remains to be explained, Luo said. Luo and his fellow researchers are still trying to figure out why clay hydrogel is such a successful material in cell-free protein production.
This is important because it examines clays interaction with many organic activities throughtout the history of the Earth. It is important for me to lay down some text explaining what clay is and what it could be called.
From Wikipedia, the free encyclopedia
Clay is a fine-grained soil that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.
Clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays, but there is some overlap in both particle size and other physical properties, and there are many naturally occurring deposits which include silts and also clay. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 4-5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils’ Atterberg Limits. ISO 14688 grades clay particles as being smaller than 2 μm and silts larger.
Colloidal and chemical properties
The chemistry of soil determines the availability of nutrients, the health of microbial populations, and its physical properties. In addition, soil chemistry also determines its corrosivity, stability, and ability to absorb pollutants and to filter water. It is the surface chemistry of clay and humus colloids that determines soil’s chemical properties. “A colloid is a small, insoluble, nondiffusible particle larger than a molecule but small enough to remain suspended in a fluid medium without settling. Most soils contain organic colloidal particles called humus as well as the inorganic colloidal particles of clays.” The very high specific surface area of colloids and their net negative charges, gives soil its great ability to hold and release cations in what is referred to as cation exchange. Cation-exchange capacity (CEC) is the amount of exchangeable cations per unit weight of dry soil and is expressed in terms of milliequivalents of hydrogen ion per 100 grams of soil.
Mineral Colloids; Soil clays
Due to its high specific surface area and its unbalanced negative charges, clay is the most active mineral component of soil. It is a colloidal and most often a crystalline material. In soils, clay is defined in a physical sense as any mineral particle less than 2 µm (8×10−5 in) in effective diameter. Chemically, clay is a range of minerals with certain reactive properties. Clay is also a soil textural class. Many soil minerals, such as gypsum, carbonates, or quartz, are small enough to be classified physically as clay but chemically do not afford the same utility as do clay minerals.
Clay was once thought to be very small particles of quartz, feldspar, mica, hornblende or augite, but it is now known to be (with the exception of mica-based clays) a precipitate with a mineralogical composition that is dependent on but different from its parent materials and is classed as a secondary mineral. The type of clay that is formed is a function of the parent material and the composition of the minerals in solution. Clay minerals continue to be formed as long as the soil exists. Mica-based clays result from a modification of the primary mica mineral in such a way that it behaves and is classed as a clay. Most clays are crystalline, but some are amorphous. The clays of a soil are a mixture of the various types of clay, but one type predominates.
Most clays are crystalline and most are made up of three or four planes of oxygen held together by planes of aluminium and silicon by way of ionic bonds that together form a single layer of clay. The spatial arrangement of the oxygen atoms determines clay’s structure. Half of the weight of clay is oxygen, but on a volume basis oxygen is ninety percent. The layers of clay are sometimes held together through hydrogen bonds or potassium bridges and as a result swell less in the presence of water. Other clays, such as montmorillonite, have layers that are loosely attached and will swell greatly when water intervenes.
There are three groups of clays:
- Crystalline alumino-silica clays: montmorillonite, illite, vermiculite, chlorite, kaolinite.
- Amorphous clays: young mixtures of silica (SiO2-OH) and alumina (Al(OH)3) which have not had time to form regular crystals.
- Sesquioxide clays: old, highly leached clays which result in oxides of iron, aluminium and titanium.
- Alumino-silica clays are characterised by their regular crystalline structure. Oxygen in ionic bonds with silicon forms a tetrahedral coordination which in turn forms sheets of silica. Two sheets of silica are bonded together by a plane of aluminium which forms an octahedral coordination, called alumina, with the oxygens of the silica sheet above and that below it. Hydroxyl ions (OH–) sometimes substitute for oxygen. During the clay formation process, Al3+ may substitute for Si4+, and as much as one fourth of the aluminium Al3+ may be substituted by Zn2+, Mg2+ or Fe2+. The substitution of lower-valence cations for higher-valence cations (isomorphic substitution) gives clay a net negative charge that attracts and holds soil cations, some of which are of value for plant growth. Isomorphic substitution occurs during the clay’s formation and does not change with time.
- Montmorillonite clay is made of four planes of oxygen with two silicon and one central aluminium plane intervening. The alumino-silicate montmorillonite clay is said to have a 2:1 ratio of silicon to aluminium. The seven planes together form a single layer of montmorillonite. The layers are weakly held together and water may intervene, causing the clay to swell up to ten times its dry volume. It occurs in soils which have had little leaching, hence it is found in arid regions. The entire surface is exposed and available for surface reactions and it has a high cation exchange capacity (CEC).
- Illite is a 2:1 clay similar in structure to montmorillonite but has potassium bridges between the clay layers and the degree of swelling depends on the degree of weathering of the potassium. The active surface area is reduced due to the potassium bonds. Illite originates from the modification of mica, a primary mineral. It is often found together with montmorillonite and its primary minerals. It has moderate CEC.
- Vermiculite is a mica-based clay similar to illite, but the layers of clay are held together more loosely by hydrated magnesium and it will swell, but not as much as does montmorillonite. It has very high CEC.
- Chlorite is similar to vermiculite, but the loose bonding by occasional hydrated magnesium is replaced by a hydrated magnesium sheet, firmly bonding the planes above and below it. It has two planes of silicon, one of aluminium and one of magnesium; hence it is a 2:2 clay. Chlorite does not swell and it has low CEC.
- Kaolinite is very common, more common than montmorillonite in acid soils. It has one silica and one alumina sheet per layer; hence it is a 1:1 type clay. One layer of oxygen is replaced with hydroxyls, which produces strong hydrogen bonds to the oxygen in the next layer of clay. As a result kaolinite does not swell in water and has a low specific surface area, and as almost no isomorphic substitution has occurred it has a low CEC. Where rainfall is high, acid soils selectively leach more silica than alumina from the original clays, leaving kaolinite. Even heavier weathering results in sesquioxide clays.
- Amorphous clays are young, and commonly found in volcanic ash. They are mixtures of alumina and silica which have not formed the ordered crystal shape of alumino-silica clays which time would provide. The majority of their negative charges originates from hydroxyl ions, which can gain or lose a hydrogen ion (H+) in response to soil pH, and hence buffer the soil pH. They may have either a negative charge provided by the attached hydroxyl ion (OH–), which can attract a cation, or lose the hydrogen of the hydroxyl to solution and display a positive charge which can attract anions. As a result they may display either high CEC, in an acid soil solution, or high anion exchange capacity, in a basic soil solution.
- Sesquioxide clays are a product of heavy rainfall that has leached most of the silica and alumina from alumino-silica clay, leaving the less soluble oxides of iron Fe2O3 and iron hydroxide (Fe(OH)3) and aluminium hydroxides (Al(OH)3). It takes hundreds of thousands of years of leaching to create sesquioxide clays. Sesqui is Latin for “one and one-half”: there are three parts oxygen to two parts iron or aluminium; hence the ratio is one and one-half. They are hydrated and act as either amorphous or crystalline. They are not sticky and do not swell, and soils high in them behave much like sand and can rapidly pass water. They are able to hold large quantities of phosphates. Sesquioxides have low CEC. Such soils range from yellow to red in colour. Such clays tend to hold phosphorus tightly rendering them unavailable for absorption by plants.
Above I have highlighted the parts about organic matter as well as the term “soil”. I think that is important when discussing a narrow band of text about soil specifically for bonsai. For years, decades, terms used in books to explain what a bonsai should be planted in have been termed soil, loam, organic, and inorganic
Soil is the mixture of minerals, organic matter, gases, liquids and a myriad of micro– and macro- organisms that can support plant life. It is a natural body that exists as part of the pedosphere and it performs four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of the atmosphere; and it is a habitat for organisms that take part in decomposition and creation of a habitat for other organisms.
Soil is considered the “skin of the earth” with interfaces between the lithosphere, hydrosphere, atmosphere, and biosphere. Soil consists of a solid phase (minerals & organic matter) as well as a porous phase that holds gases and water. Accordingly, soils are often treated as a three-state system.
Soil is the end product of the influence of the climate, relief (elevation, orientation, and slope of terrain), biotic activities (organisms), and parent materials (original minerals) acting over periods of time. Soil continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion.
Most soils have a density between 1 and 2 g/cm3. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, although fossilized soils are preserved from as far back as the Archean.
Soil science has two main branches of study: Edaphology and Pedology (from Greek: pedon, “soil”; and logos, “study”). Pedology is focused on the formation, morphology, and classification of soils in their natural environment., whereas Edaphology is concerned with the influence of soils on organisms. In engineering terms, soil is referred to as regolith, or loose rock material that lies above the ‘solid geology’. Soil is commonly referred to as “earth” or “dirt“; technically, the term “dirt” should be restricted to displaced soil.[12
Loam is soil composed of sand, silt, and clay in relatively even proportions (about 40%-40%-20% concentration respectively). These proportions can vary to a degree however, and result in different types of loam soils: sandy loam, silty loam, clay loam, sandy clay loam, silty clay loam, and loam. Loam soils generally contain more nutrients, moisture, and humus than sandy soils, have better drainage and infiltration of water and air than silty soils, and are easier to till than clay soils. The different types of loam soils each have slightly different characteristics, with some draining liquids more efficiently than others.
Loam is considered ideal for gardening and agricultural uses because it retains nutrients well and retains water while still allowing excess water to drain away. A soil dominated by one or two of the three particle size groups can behave like loam if it has a strong granular structure, promoted by a high content of organic matter. However, a soil that meets the textural definition of loam can lose its characteristic desirable qualities when it is compacted, depleted of organic matter, or has clay dispersed throughout its fine-earth fraction.
|a Histosol profile|
|Used in:||WRB, USDA soil taxonomy, other|
|Parent material:||Organic matter|
In both the FAO soil classification and the USDA soil taxonomy, a histosol is a soil consisting primarily of organic materials. They are defined as having 40 centimetres (16 in) or more of organic soil material in the upper 80 centimetres (31 in). Organic soil material has an organic carbon content (by weight) of 12 to 18 percent, or more, depending on the clay content of the soil. These materials include muck (sapric soil material), mucky peat (hemic soil material), or peat (fibric soil material). Aquic conditions or artificial drainage are required. Typically, histosols have very low bulk density and are poorly drained because the organic matter holds water very well. Most are acidic and many are very deficient in major plant nutrients which are washed away in the consistently moist soil.
Histosols form whenever organic matter forms at a more rapid rate than it is destroyed. This occurs because of restricted drainage precluding aerobic decomposition, and the remains of plants and animals remain within the soil. Thus, histosols are very important ecologically because they, and gelisols, store large quantities of organic carbon. If accumulation continues for a long enough period, coal forms.
Most histosols occur in Canada, Scandinavia, the West Siberian Plain, Sumatra, Borneo and New Guinea. Smaller areas are found in other parts of Europe, the Russian Far East (chiefly in Khabarovsk Krai and Amur Oblast), Florida and other areas of permanent swampland. Fossil histosols are known from the earliest extensive land vegetation in the Devonian.
Histosols are generally very difficult to cultivate because of the poor drainage and often low chemical fertility. However, histosols formed on very recent glacial lands can often be very productive when drained and produce high-grade pasture for dairying or beef cattle. They can sometimes be used for fruit if carefully managed, but there is a great risk of the organic matter becoming dry powder and eroding under the influence of drying winds. A tendency towards shrinkage and compaction is also evident with crops.
- Conifer bark – in particular, “aged pine bark” or “aged fir bark”. Conifer bark is often sold as “orchid bark” (since orchids are usually planted in pure bark), as soil conditioner made of “decomposed pine bark” or the like, and as mulch. Most sources of conifer bark must be screened to remove large pieces (larger than about 1/4″ or 1/8″) and very small pieces (smaller than about 1/16″).
- Peat moss – retains a lot of water, so it is used sparingly. Peat moss is slightly acidic; some plants (in particular, azaleas) need acidic conditions to thrive.
- Potting soil – not widely recommended, but it works and is easy to find. May also contain slow-release fertilizer pellets, which can supplement periodic fertilization.
- Leftovers – the decomposed organic components from used soil is often the most convenient source of water-retaining organic material, especially soil from the same tree. There may be a danger of transferring harmful microorganisms (such as root rot). Keeping some soil from a previous potting is also a way to preserve helpful microorganisms (such as the symbiotic Mycorrhizae fungus), which is especially important for pine trees (although not as important as proper soil drainage!).
Soil with less than 20 percent organic matter in the upper 16 inches. An inorganic compound is a compound that is not considered “organic“. Inorganic compounds are traditionally viewed as being synthesized by the agency of geological systems. In contrast, organic compounds are found in biological systems. Organic chemists traditionally refer to any molecule containing carbon as an organic compound and by default this means that inorganic chemistry deals with molecules lacking carbon. The 19th century chemist, Berzelius, described inorganic compounds as inanimate, not biological, origin, although many minerals are of biological origin. Biologists may distinguish organic from inorganic compounds in a different way that does not hinge on the presence of a carbon atom. Pools of organic matter, for example, that have been metabolically incorporated into living tissues persist in decomposing tissues, but as molecules become oxidized into the open environment, such as atmospheric CO2, this creates a separate pool of inorganic compounds. The distinction between inorganic and organic compounds is not always clear. Some scientists, for example, view the open environment (i.e., the ecosphere) as an extension of life and from this perspective may consider atmospheric CO2 as an organic compound. The International Union of Pure and Applied Chemistry, an agency widely recognized for defining chemical terms, does not offer definitions of inorganic or organic. Hence, the definition for an inorganic versus an organic compound in a multidisciplinary context spans the division between living (or animate) and non-living (or inanimate) matter and remains open to debate according to the way that one views the world.
In many cases, “soil” is actually a misnomer, as the potting medium may contain no soil in the traditional sense. For trees growing in nature, the decaying organic matter in soil provides nutrients necessary for growth. In bonsai, limited soil volume means than any nutrients from natural organic matter is quickly depleted, so fertilizer and sometimes other supplements are added to the potting medium to provide nutrition. The fine particles of clay and organic matter in potting soil and most natural types of soil hold too much water and not enough air for all the but the most water-loving bonsai, so bonsai soils usually contain generous portions of course inorganic particles, such as grit and/or porous clay. These inorganic particles allow water to drain freely and create numerous small air pockets in the soil. Baked clay particles (including natural volcanic clays such akadama) also retain water and nutrients. To hold more water, most bonsai soils also contain some kind of organic component; the most common choice is small pieces of conifer bark (e.g., pine bark or fir bark), which provides better drainage and breaks down slower than peat moss or generic potting soil.
- Akadama – the traditional soil of Japanese bonsai. A natural volcanic clay surface-mined in Japan, akadama is an expensive (and fast-disappearing) soil component. It breaks down relatively quickly (a year or two) when exposed to freezing and thawing, but many bonsai artists attest to superior root development compared to manufactured substitutes.
- Arcillite – baked montmorillonite clay, sold as Turface, Schultz Aquatic Soil, and other products. Arcillite has an attractive reddish color that darkens to brown when wet. It has high nutrient-retention properties, and is very stable and long-lasting.
- Baked fuller’s earth – variable baked clay products, sold as an oil absorbent (e.g., Oil-Dri) and a variety of cat litters (e.g., Johnny Cat), among other products. The most economical, and often easiest to find, porous clay component. Some types of baked clay break down faster than others, and some are less attractive than others.
- Horticultural perlite – A very light-weight, fast-draining substance that holds a small amount of water. Perlite floats in water, breaks apart easily, and can be quite the eyesore on the soil surface. However, it is a helpful component in large pots, which can be extremely heavy when filled with dense soil components.
- Horticultural vermiculite- A light-weight, brown substance than retains more water than perlite.
- Crushed granite – an inert, non-porous particle that promotes drainage, often sold as poultry grit. The sharp edges are thought to stimulate splitting of roots and the growth of many small drinking roots.
- Flint grit – an inert, non-porous particle like crushed granite.
Soil organic matter
From Wikipedia, the free encyclopedia
Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal residues at various stages of decomposition, cells and tissues of soil organisms, and substances synthesized by soil organisms. SOM exerts numerous positive effects on soil physical and chemical properties, as well as the soil’s capacity to provide regulatory ecosystem services. Particularly, the presence of SOM is regarded as being critical for soil function and soil quality.
The positive impacts of SOM result from a number of complex, interactive edaphic factors; a non-exhaustive list of SOM’s effects on soil functioning includes improvements related to soil structure, aggregation, water retention, soil biodiversity, absorption and retention of pollutants, buffering capacity, and the cycling and storage of plant nutrients. SOM increases soil fertility by providing cation exchange sites and acting as reserve of essential nutrients, especially nitrogen (N), phosphorus (P), and sulfur (S), along with micronutrients, which are slowly released upon SOM mineralization[disambiguation needed]. As such, there is a significant correlation between SOM content and soil fertility.
SOM also acts the major sink and source of soil carbon. Given that SOM is typically estimated to contain 58% C (CITATION NEEDED), the terms ‘soil organic carbon’ (SOC) and SOM are often used interchangeably, with measured SOC content often serving as a proxy for SOM. Soil represents one of the largest C sinks on the planet and plays a major role in the global carbon cycle. Therefore, SOM/SOC dynamics and the capacity of soils to provide the ecosystem service of carbon sequestration through SOM management have received considerable attention in recent years.
The mass of SOM in soils as a percent generally ranges from 1 to 6% of the total topsoil mass for most upland soils. Soils whose upper horizons consist of less than 1% organic matter are mostly limited to desert areas, while the SOM content of soils in low-lying, wet areas can be as high as 90%. Soils containing 12-18% SOC are generally classified as organic soils.
It can be divided into three general pools: living biomass of microorganisms, fresh and partially decomposed residues, and humus: the well-decomposed organic matter and highly stable organic material. Surface litter is generally not included as part of soil organic matter.
Soil Organic Matter: The Living, the Dead, and the Very Dead
Vern Grubinger Vegetable and Berry Specialist University of Vermont Extension
Soil organic matter makes up only a few percent of most soils, but it has a great deal of influence on soil properties, and in turn, agricultural productivity.
What does it do? The list of soil properties affected by soil organic matter is long. It includes: aggregate stability (how well tiny clumps of soil hold together, which affects soil structure); cation exchange capacity (the ability of soil to hold onto positively charged nutrients for plant growth), nutrient release rate by mineralization (how much nitrogen, phosphorus and other elements are given off by microbial activity), and water-holding capacity.
How much is there? The amount of soil organic matter in a particular location is primarily due to natural factors like temperature (cool locations accumulate more organic matter), soil texture (clayey and silty soils tend to have more organic matter than sandy soils), and the drainage (poor drainage promotes soil organic matter build up). However, management also affects soil organic matter level, and it is not unusual for that level to decline over time in cultivated fields. Frequent tillage, periods of bare ground, and removal of crop residues all contribute to reductions in soil organic matter.
What is it? Soil organic matter is made up of plant and animal residues in different stages of decomposition, cells of soil microorganisms, and substances that are so well-decomposed it’s impossible to tell what they were to begin with.
Living organisms are also considered to be part of soil organic matter, and they play a big role in contributing organic residues to the soil and in formation of more stable types of organic matter. Plant roots and various soil animals (rodents, earthworms, mites, etc.) all provide organic materials to the soil that eventually become part of the soil organic matter cycle. There are four main processes in that cycle, and all of them rely on soil microbes: decomposition of organic residues, release of nutrients (mineralization), release of carbon dioxide (respiration), and transfer of carbon from one soil organic matter ‘pool’ to another.
Not just one kind of organic matter. In addition to organic matter that is alive, there are three types, or pools, of “dead” soil organic matter: active, slow, and passive. These are determined by the time it takes for them to completely decompose.
Active soil organic matter is primarily made up of fresh plant and animal residues that break down in a very short time, from a few weeks to a few years. This kind of organic matter is associated with a lot of biological activity. Passive soil organic matter, also known as humus, is not biologically active, meaning it provides very little food for soil organisms. It may take hundreds or even thousands of years to fully decompose! Slow soil organic matter is somewhere in between active and passive soil organic matter. It consists primarily of detritus, partially broken down cells and tissues that are only gradually decomposing. Slow soil organic matter is somewhat resistant to decay and may take a few years to a few decades to completely break down.
What is Humus? Hummus (with two m’s) is a middle-eastern food made from chick peas. Humus (one m) is the passive fraction of soil organic matter. It is a dark, complex mixture of organic substances that have been significantly modified from their original form over time, and it also contains other substances that have been synthesized by soil organisms. Usually, humus represents the majority of total soil organic matter, and it is relatively stable over time.
Humus has a lot to do with the ability of a soil to retain nutrients and water. Humus also supplies organic chemicals to the soil solution that can serve as chelates, which can hang onto trace elements and increase their availability to plants.
What is active soil organic matter? Active soil organic matter is ‘fresh meat’ to microbes. It is the readily digestible and easily decomposed portion of fresh organic (meaning carbon-containing) residues. Active soil organic matter plays a very different role than passive organic matter does. As it is decomposed by soil organisms it helps stabilize soil aggregates, it releases nutrients by mineralization, and it provides food for microbial activity, which can lead to suppression of plant diseases and enhanced plant growth.
The amount of active organic matter in the soil can change quickly, in just a year or two, and it’s highly influenced by soil management practices. To maintain the same level of active soil organic matter requires a constant supply of fresh organic materials, usually from growing plants. Crop roots, crop residues and cover crops all contribute to active organic matter. Soil must also be managed to minimize the loss of organic matter through oxidation (from aggressive tillage) and erosion (from ground left bare).
The amount of active soil organic matter and the proportion it makes up of total soil organic matter are good indicators of soil health. Unfortunately, most soil tests don’t differentiate between the different forms of soil organic matter; they just report the percent of soil that is total organic matter. As a result, farmers aren’t able to determine what is going on with their soil organic matter pools, and they can’t monitor how their management practices are affecting active soil organic matter levels.
The good news is that soil scientists are working to develop affordable tests active soil organic matter, and these should be commercially available in the near future.
Role in carbon cycling
Soil plays a major role in the global carbon cycle, with the global soil carbon pool is estimated at 2500 gigatons. This is 3.3 times the size of the atmospheric pool (750 gigatons) and 4.5 times the biotic pool (560 gigatons). The pool of organic carbon, which occurs primarily in the form of SOM, accounts roughly 1550 gigatons of the total global C pool, with the remainder accounted for by soil inorganic carbon (SIC). The pool of organic C exists in dynamic equilibrium between gains and losses; soil may therefore serve as either a sink or source of C, through sequestration or greenhouse gas emissions, respectively, depending on exogenous factors (Lal, 2004).
The last few thousand paragraphs have broken soil into groups and how those groups react in nature. The one thread winding its way through all the soils i SOM, Soil Organic Matter. Tghis SOM also called humas is part of the equation which makes organic additions to bonsai soil mixes work.
Humic acid is a principal component of humic substances, which are the major organic constituents of soil (humus), peat, coal, many upland streams, dystrophic lakes, and ocean water. It is produced by biodegradation of dead organic matter. It is not a single acid; rather, it is a complex mixture of many different acids containing carboxyl and phenolate groups so that the mixture behaves functionally as a dibasic acid or, occasionally, as a tribasic acid. Humic acids can form complexes with ions that are commonly found in the environment creating humic colloids. Humic and fulvic acids (fulvic acids are humic acids of lower molecular weight and higher oxygen content than other humic acids) are commonly used as a soil supplement in agriculture, and less commonly as a human nutritional supplement. As a nutrition supplement, fulvic acid can be found in a liquid form as a component of mineral colloids. Fulvic acids are poly-electrolytes and are unique colloids that diffuse easily through membranes whereas all other colloids do not. “Synthesis of fulvic acid (1a) was accomplished by a route involving selective ozonization of 9-propenylpyranobenzopyran (1c), obtained by a regioselective cyclization of the 2-methylsulphinylmethyl 1,3-dione(3c).”
Humic substances are formed by the microbial degradation of dead plant matter, such as lignin. They are very resistant to further biodegradation. The precise properties and structure of a given sample depend on the water or soil source and the specific conditions of extraction. Nevertheless, the average properties of humic substances from different sources are remarkably similar.
Humic substances in soils and sediments can be divided into three main fractions: humic acids, fulvic acids, and humin. The humic and fulvic acids are extracted as a colloidal sol from soil and other solid phase sources into a strongly basic aqueous solution of sodium hydroxide or potassium hydroxide. Humic acids are precipitated from this solution by adjusting the pH to 1 with hydrochloric acid, leaving the fulvic acids in solution. This is the operational distinction between humic and fulvic acids. Humin is insoluble in dilute alkali. The alcohol-soluble portion of the humic fraction is, in general, named ulmic acid. So-called “gray humic acids” (GHA) are soluble in low-ionic-strength alkaline media; “brown humic acids” (BHA) are soluble in alkaline conditions independent of ionic strength; and fulvic acids (FA) are soluble independent of pH and ionic strength.
Liquid chromatography and liquid-liquid extraction can be used to separate the components that make up a humic substance. Substances identified include mono-, di-, and tri-hydroxy acids, fatty acids, dicarboxylic acids, linear alcohols, phenolic acids, and terpenoids.
Organic matter soil amendments have been known by farmers to be beneficial to plant growth for longer than recorded history. However, the chemistry and function of the organic matter have been a subject of controversy since humans began their postulating about it in the 18th century. Until the time of Liebig, it was supposed that humus was used directly by plants, but, after Liebig had shown that plant growth depends upon inorganic compounds, many soil scientists held the view that organic matter was useful for fertility only as it was broken down with the release of its constituent nutrient elements into inorganic forms. At the present time, soil scientists hold a more holistic view and at least recognize that humus influences soil fertility through its effect on the water-holding capacity of the soil. Also, since plants have been shown to absorb and translocate the complex organic molecules of systemic insecticides, they can no longer discredit the idea that plants may be able to absorb the soluble forms of humus; this may in fact be an essential process for the uptake of otherwise insoluble iron oxides.
A study on the effects of Humic acid on plant growth was conducted at Ohio State University which said in part “humic acids increased plant growth” and that there were “relatively large responses at low application rates” 
Humus is the penultimate state of decomposition of organic matter; while it may linger for a thousand years, on the larger scale of the age of the other soil components, it is temporary. It is composed of the very stable lignins (30%) and complex sugars (polyuronides, 30%), proteins (30%), waxes, and fats. Its chemical assay is 60% carbon, 5% nitrogen, some oxygen and the remainder hydrogen, sulfur, and phosphorus. On a dry weight basis, the CEC of humus is many times greater than that of clay.[94
Cation Exchange Capacity in Soils, Simplified
(so that even I can understand it.)
©2007 by Michael Astera
All rights reserved
Revised Oct.31, 2008
Adsorb vs Absorb
adsorb (ad sôrb, -zôrb), v.t. Physical Chem. to gather (a gas, liquid, or dissolved substance) on a surface in a condensed layer: Charcoal will adsorb gases .
Please note the definition above, taken from my handy dictionary, flower press, and child booster seat, the real hardbound Random House second edition unabridged. It’s not absorb, it’s adsorb , with a “d”. We all know that a sponge absorbs water, a cast iron pot absorbs heat, a flat-black wall absorbs light. None of those gathers anything on the surface in a condensed layer, they soak it right in, they absorb it.
Adsorb is different, because it means to gather on a surface in a condensed layer . This is pretty much the same thing as static cling, like when you take a synthetic fabric shirt out of the clothes dryer and it wants to stick to you. You don’t absorb the nylon blouse, you adsorb it. Everyone got that? Good. On to Cation Exchange Capacity.
The Exchange Capacity of your soil is a measure of its ability to hold and release various elements and compounds. We are mostly concerned with the soil’s ability to hold and release plant nutrients, obviously. Specifically here today, we are concerned with the soil’s ability to hold and release positively charged nutrients. Something that has a positive (+) charge is called a cation, pronounced cat-eye-on. If it has a negative charge (-) it is called an anion, pronounced ann-eye-on. (Both words are accented on the first syllable.) The word “ion” simply means a charged particle; a positive charge is attracted to a negative charge and vice-versa.
Positively charged particles are known as cations. There are two types of cations, acidic or acid-forming cations, and basic, or alkaline-forming cations. The Hydrogen cation H+ and the Aluminum cation Al+++ are acid-forming. Niether are plant nutrients. A soil with high levels of H+ or Al+++ is an acid soil, with a low pH.
The positively charged nutrients that we are mainly concerned with here are Calcium, Magnesium, Potassium and Sodium. These are all alkaline cations, also called basic cations or bases. Both types of cations may be adsorbed onto either a clay particle or soil organic matter (SOM). All of the nutrients in the soil need to be held there somehow, or they will just wash away when you water the garden or get a good rainstorm. Clay particles almost always have a negative (-) charge, so they attract and hold positively (+) charged nutrients and non-nutrients. Soil organic matter (SOM) has both positive and negative charges, so it can hold on to both cations and anions.
Both the clay particles and the organic matter have negatively charged sites that attract and hold positively charged particles. Cation Exchange Capacity is the measure of how many negatively-charged sites are available in your soil.
The Cation Exchange Capacity of your soil could be likened to a bucket: some soils are like a big bucket (high CEC), some are like a small bucket (low CEC). Generally speaking, a sandy soil with little organic matter will have a very low CEC while a clay soil with a lot of organic matter (as humus) will have a high CEC. Organic matter (as humus) always has a high CEC; with clay soils, it depends on the type of clay.
Base Saturation %
From the 1920s to the late 1940s, a great and largely un-sung hero of agriculture, Dr. William Albrecht, did a lot of experimenting with different ratios of nutrient cations, the Calcium, Magnesium, Potassium and Sodium mentioned above. He and his associates, working at the University of Missouri Agricultural Experiment Station, came to the conclusion that the strongest, healthiest, and most nutritious crops were grown in a soil where the soil’s CEC was saturated to about 65% Calcium, 15% Magnesium, 4% Potassium, and 1% to 5% Sodium. (No, they don’t add to 100%; we’ll get to that.) This ratio not only provided luxury levels of these nutrients to the crop and to the soil life, but it strongly affected the soil texture and pH.
The percentage of the CEC that a particular cation occupies is also known as the base saturation percentage, or percent of base saturation, so another way of describing Albrecht’s ideal ratio is that you want 65% base saturation of Calcium, 15% base saturation of Magnesium etc. Don’t get too hung up on these percentages; they are general guidelines and can vary quite a bit depending on soil texture and other factors.
It’s still a little-known fact that the Calcium to Magnesium ratio determines how tight or loose a soil is. The more Calcium a soil has, the looser it is; the more Magnesium, the tighter it is, up to a point. Other things being equal, a high Calcium soil will have more oxygen, drain more freely, and support more aerobic breakdown of organic matter, while a high Magnesium soil will have less oxygen, tend to drain slowly, and organic matter will break down poorly if at all. In a soil with Magnesium higher than Calcium, organic matter may ferment and produce alcohol and even formaldehyde, both of which are preservatives. If you till up last years cornstalks and they are still shiny and green, you likely have a soil with an inverted Calcium/Magnesium ratio. On the other hand, if you get the Calcium level too high, the soil will lose all its beneficial granulation and structure and the too-high Calcium will interfere with the availability of other nutrients. If you get them just right for your particular soil, you can drive over the garden and not have a problem with soil compaction.
Because Calcium tends to loosen soil and Magnesium tightens it, in a heavy clay soil you may want 70% Calcium and 10% Magnesium; in a loose sandy soil 60% Ca and 20% Mg might be better because it will tighten up the soil and improve water retention. If together they add to 80%, with about 4% Potassium and 1-3% Sodium, that leaves 12-15% of the exchange capacity free for other elements, and an interesting thing happens. 4 or 5% of that CEC will be filled with other bases such as Copper and Zinc, Iron and Manganese, and the remainder will be occupied by exchangeable Hydrogen , H+. The pH of the soil will automatically stabilize at around 6.4 , which is the “perfect soil pH” not only for organic/biological agriculture, but is also the ideal pH of sap in a healthy plant, and the pH of saliva and urine in a healthy human.
So we are looking at two new things so far:
1) The Cation Exchange Capacity, and
2) The proportion of those cations in relation to each other: the percent of base saturation (% base saturation) and their effect on pH.
We are also looking at two old familiar things, clay and soil organic matter, and these last two need a bit more clarification.
How Clay and Humus Form
Clay particles are really tiny; I mean really. really tiny. They are so small that they can’t even be seen in most microscopes. They are so small that when mixed in water they may take days, weeks, or months to settle out, or they may never settle out and just remain suspended in the water; not dissolved, but suspended. A particle that remains suspended in water like this, suspended but not dissolved, is known as a colloid . Organic matter, as it breaks down, also forms smaller and smaller particles, until it breaks down as far as it can go and still be organic matter. At that stage it is called humus , and humus is also a colloid; when mixed into water humus will not readily settle out or float to the top. Colloids, because they are so small, have a very large surface area per unit volume or by weight. Some clays, such as montmorillonite and vermiculite, have a surface area as high as 800 square meters per gram, over 200,000 square feet (almost five acres) per ounce! The surface area of fully developed humus is about the same or even higher. Other clays have a much lower surface area, and some clays actually have a very low exchange capacity, while humus always has a high exchange capacity.
Mineral soils are formed by the breakdown of rocks, known as the parent material . Heating and cooling, freezing and thawing, wind and water erosion, acid rain (all rain is acid; carbon dioxide in the air forms carbonic acid in the rain), and biological activity all break down the parent material into finer and finer particles. Eventually the particles get so small that some of them re-form, that is they re-crystallize into tiny flat platelets, and become colloidal clay, made up mostly of silica and alumina. These clay particles aggregate into thin, flat sheets that stack together in layers.
How old a soil is usually determines how much clay it has. The more rainfall a soil gets, the faster it breaks down into clay. Arid regions are mostly sandy and rocky soil, unless they have areas of “fossil” clay. River bottoms in arid regions will often have more clay because the small clay particles wash away easily from areas without vegetation cover. As noted above, clays tend to stick together in microscopic layers. Newly formed clays will often be made up of layers of silica and alumina sandwiched with potassium or iron. On these young clays, the only available exchange sites are on the edges. As the clays age, the “filling” in the sandwich gets taken out by acid rain or soil life or plant roots, opening up more and more negatively charged exchange sites and increasing the exchange capacity. Eventually these clays become tiny layers of silica and alumina separated by a thin film of water. These are the expanding clays ; when they get wet they swell, and when they dry out they shrink and crack deeply. Because these expanding clays have exchange sites available between their layers and not just on the edges, they have a much greater exchange capacity than freshly formed clays. Over millions of years, the space in these expanding clays gets filled back in with hydrated aluminum oxide and they lose their exchange capacity again, this time permanently.
In the southern half of the USA, the age of the clay fraction of the soil generally increases going from West to East. The arid regions, from California to western Texas, are largely young soils, containing a lot of sand and gravel and some young clays without a lot of exchange capacity. The central regions, from West-central Texas and above into Oklahoma, Kansas, and Nebraska, contain well-developed clays with high CEC. Moving East, the rainfall increases, the soils are older, and the clays are generally aged and have lost much of their ability to exchange cations. Across Louisiana, Mississippi, Alabama, and Georgia the clays have been rained on and leached out for millions of years. Their reserves of Calcium and Magnesium are often long gone. The northern tier states, from Washington in the West to Pennsylvania and New York in the East were largely covered with glaciers as recently as 10,000 years ago, which brought them a fresh supply of minerals, and clays of high exchange capacity are common.
Organic Matter and Humus
Regarding soil organic matter (SOM) and humus, obviously any area that gets more rainfall tends to grow more vegetation, so the fraction of the soil that is made up of decaying organic matter will usually increase with more rainfall. Breakdown of organic matter is largely dependent on moisture, temperature, and availability of oxygen. As any of these increase, the organic matter usually breaks down faster. Moisture and oxygen being equal, colder northern areas will tend to build up more organic matter in the soil than hotter southern climates, with one extreme being found in the tropics where organic matter breaks down and disappears very quickly, and the other extreme being the vast. deep peat beds and “muck” soils of some northern states. As always, there are exceptions, such as the everglades of Florida, where lack of oxygen combined with stagnant water have formed the largest peat beds in the world; the area around Sacramento California is another example: there were muck soils 100 feet deep when that delta was first farmed by European settlers.
Ordinary organic matter from the compost or manure pile, or the remains of last years crops, doesn’t have much exchange capacity until it has been broken down into humus, and from what we know, the formation of humus seems to require the action of soil microorganisms, earthworms, fungi, and insects. When none of them can do anything with it as food anymore, it has ended up as a very small but very complex carbon structure (a colloid) that can hold and release many times its weight in water and plant nutrients. The higher the humus level of the soil, the greater the exchange capacity. The only way to increase humus in your soil is by adding organic matter and having healthy soil life to break it down, or to add a soil amendment such as lignite (also known as Leonardite), a type of soft coal that contains large amounts of humus and humic acids. Humus and humic acids have an exchange capacity greater than even the highest CEC clays.
OK, lets pull this information together. We have discovered that:
1) Alkaline soil nutrients, largely Calcium, Magnesium, Potassium, and Sodium, are positively charged cations (+) and are held on negatively charged (-) sites on clay and humus.
2) The amount of humus, and the amount and type of clay, determine how much Cation Exchange Capacity a given soil has.
3) We have also discussed the ideal base saturation percentages of these nutrients, approximately:
4% K (Potassium),
1-3% Na (Sodium)
4) We have talked a little about the effect of those ratios on soil texture and pH and why they are not hard and fast “rules”.
The next step is understanding how the plant, and the soil life, gets those nutrients from the exchange sites, the “exchange” part of the story.
Trading + for +
In the same way that acid rain can leach cations from the soil, plants and soil microorganisms more or less “leach” the cation nutrients from their exchange sites. These alkaline nutrients are only held on the surface with a weak, static electrical charge, i.e. they are “adsorbed”. They are constantly oscillating and moving a bit, pulled and pushed this way and that by other charged particles (ions) in the soil solution around them. What the plant roots and soil microorganisms do is exude or give off Hydrogen ions, H+ ions, and if enough of these H+ ions are given off that some of them surround the nutrient cation and get closer to the negatively (-) charged exchange site than the nutrient is, the H+ ions will fill the exchange site, neutralize the (- ) charge, and the nutrient cation will be free of its static bond and can then be taken up by the plant or microorganism.
The way this works specifically with plant roots is that the plant roots expire or breathe out carbon dioxide into the soil. This carbon dioxide (CO 2 ) combines with water in the soil and forms carbonic acid, and the H+ Hydrogen ions from the carbonic acid are what replaces the cation nutrient on the exchange site. The Calcium ion that is held to the exchange site has a double-positive charge, written Ca++. When enough H+ ions surround it that some of them get closer to the exchange site than the Ca++ ion is, two H+ ions replace the Ca++ ion and the plant is free to take the Ca++ up as a nutrient. Simple as that.
Now we move on to how the CEC is measured, and then, what to do with that information once you have it.
Exchange capacity is measured in milligram equivalents, abbreviated ME or meq. A milligram is of course 1/1000th of a gram, and the milligram they are referring to is a milligram of H+ exchangeable Hydrogen. The comparison that is used is 1 milligram of H+ Hydrogen to 100 grams of soil. If all of the exchange sites on that 100 grams of soil could be filled by that 1 milligram of H+, then the soil would have a CEC of 1. One what? One ME, one meq, one milligram of Hydrogen.
Let me repeat that: 100 grams of a soil with a CEC of 1 could have all of its negative (-) exchange sites filled up or neutralized by 1/1000th of a gram of H+ exchangeable Hydrogen. If it had a CEC of 2, it would take 2 milligrams of Hydrogen H+, if its CEC was 120 it would take 120 milligrams of H+ to fill up all of the negative (-) exchange sites on 100 grams of soil.
The “equivalent” part of ME or meq means that other positively (+) charged ions could be substituted for the Hydrogen. If all of the sites were empty in that 100 grams of soil, and that soil had a CEC of 1, 20 milligrams of Calcium (Ca++), or 12 milligrams of Magnesium (Mg++), or 39 milligrams of Potassium (K+) would fill the same exchange sites as 1 milligram of Hydrogen H+.
Why the difference? Why does it take 20 times as much Calcium as Hydrogen? It’s because Calcium has an atomic weight of 40, while Hydrogen, the lightest element, has an atomic weight of 1. One atom of Calcium weighs forty times as much as one atom of Hydrogen . Calcium also has a double positive charge, Ca++, Hydrogen a single charge, H+, so each Ca++ ion can fill two exchange sites . It only takes half as many Calcium ions to fill the (-) sites, but Calcium is 40 times as heavy as Hydrogen, so it takes 20 times as much Calcium by weight to neutralize those (-) charges, or 12 times as much Magnesium (Mg++, also a double charge), or 39 times as much Potassium, by weight . (Potassium’s atomic weight is 39, and it has a single positive charge (K+), so it takes 39 times as much K+ to fill all the exchange sites, once again by weight . The amount of + charges, the amount of atoms of K+ or H+, is the same.)
What We Have Learned
We have now learned the basics of CEC, cation exchange, in the soil.
1) Clay and organic matter have negative charges that can hold and release positively charged nutrients. (The cations are adsorbed onto the surface of the clay or humus.) That static charge keeps the nutrients from being washed away, and holds them so they are available to plant roots and soil microorganisms.
2) The roots and microorganisms get these nutrients by exchanging free hydrogen ions. The free hydrogen H+ fills the (-) site and allows the cation nutrient to be absorbed by the root or microorganism.
3) The unit of measure for this exchange capacity is the milligram equivalent, ME or meq, which stands for 1 milligram (1/1000 of a gram) of exchangeable H+. In a soil with an exchange capacity (CEC) of 1, each 100 grams of soil contain an amount of negative (-) sites equal to the amount of positive (+) ions in 1/1000th of a gram of H+.