What you need to know about Soil

Discussion in 'Planting, growing, nurturing Plants' started by Bryant RedHawk, May 3, 2017.

  1. Bryant RedHawk

    Bryant RedHawk Junior Member

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    Soil Science is a chemical study of dirt, it is not about soil but rather about the base components needed for dirt to be ready to become soil.
    There is a problem with the way most people use soil science.
    Most people that want to start gardens or farms or any type of growing of plants will be advised “get a soil test” it will tell you what you need to add to grow great plants.
    When you take your samples of your land to the lab and they give you your analysis report.
    There is no mention of the biology that sample contained, only the mineral components, perhaps the particle size break down will be included in a “complete” soil analysis you will also get “micronutrient” lists.
    The report will also tell you what to do to get that point we call “normal” but it will again only be mineral additions, pH adjustment amendments and perhaps particle size amendment, all based on what is considered to be “normal, friable, land”.
    Nothing about anything biological that needs to be added will be mentioned. Why is this?
    It is because then we would not be soil scientist we would be biologist or microbiologist.
    See the problem here?

    Soil is Living, Dirt is Inert.
    In this thread we are going to gain knowledge about the mineral parts of land.
    Then we are going to gain knowledge about the living part and how these parts go together to create the medium that all life is dependent on for life, that we call soil.
    Then we are going to learn some methods for getting that hunk of land we call our own to become the best soil it can be for what we want to grow.

    Given that land usually contains decent amounts of the right minerals, fair pH range, good enough particle size distribution, enough organic matter to hold good amounts of water.
    The real issue becomes how to get those minerals into a form that the plants can actually use.
    This is not the focus of Soil Science, even though the name indicates otherwise.
    This is the goal of this thread, to get all the information needed to arrive at the perfect or as perfect as possible soil condition and health for optimal plant growth.
    While having good soil can seem to be complicated, (it can be very much so) it can also be very manageable with the right knowledge.

    Perhaps the most important things in this thread will be ways you can determine, on site, what you need to do and how to best accomplish this yourself.
    Sure you can use your plants to tell you, but that means that by the time they are showing you something is wrong, it is too late for that crop.
    I consider the most important tool for people doing what we are doing to be a microscope, without one you will never know what life your soil contains nor how much of that life your soil contains.
    Interestingly enough, that soil life will tell you more than all the comprehensive soil tests you ever have done can tell you. Why is this?
    Because most likely your land already has the quantities of minerals (at least for the most part) that what you want to grow need to be there.
    Without the right soil biota present we are not being the good steward for those plants we want to thrive, nor are we making the best use of most of the water we manage to store in the land.
    The goal here is to disperse that knowledge needed to have gardens that even in draught periods of a year or more will produce at least a decent amount of food.
    I will end this thread with some step by step methods, along with tests for making sure you are heading to that wonderful place called great soil.

    Redhawk

    This will be done in installments so it doesn't take a huge amount of space all at one time.
     
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  2. Bryant RedHawk

    Bryant RedHawk Junior Member

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    Consider a handful of soil. How does it appear to you, as dirt (a collection of minerals), or soil? At first glance it may appear very ordinary, something you routinely take for granted, it’s all the same isn’t it? However, once we make a closer inspection, we find that soil is far from ordinary, and certainly not dirt. It is the home of innumerable numbers of organisms, both easily visible and microscopic. Soil acts as Earth’s recycler, filter, purifier, and storehouse. The soil ecosystem recycles dead organisms into the building blocks of new life, it transforms toxic substances into simple compounds, it renders pathogenic organisms harmless, and it purifies and stores water as it passes through. Soil is a dynamic living system that functions as the interface between land and sky, the living and the dead. Soil is the repository of fertility and life on this planet. Even though the nature and properties of soil vary greatly by location, its role in the ecosystems and the ways in which it functions are basically constant from one place to another worldwide.
    Soils perform five key functions in the global ecosystem. Soil serves as a:
    1. medium for plant growth,
    2. regulator of water supplies,
    3. recycler of raw materials,
    4. habitat for soil organisms, and
    5. landscaping and engineering medium

    The first important function: As an anchor for plant roots and as a water holding tank for needed moisture, soil provides a hospitable place for a plant to take root. Some of the soil properties affecting plant growth include: soil texture (coarse of fine), aggregate size, porosity, aeration (permeability), and water holding capacity. This is paramount for any of us that want to grow our own food(s). A soil that is fine in texture, has good permeability, containing a good amount of humus will hold a vast amount of water. Another important function of soil is to store and supply nutrients to plants. The ability to perform this function is referred to as soil fertility. The clay and organic matter (OM) content of a soil directly influence its fertility. Greater clay and OM content will generally lead to greater soil fertility.

    The second important function: As rain or snow falls upon the land, the soil is there to absorb and store the moisture for later use. This creates a subsurface pool of available water for plants and soil organisms to live on between precipitation or irrigation events. When soils are very wet, near saturation, water moves downward through the soil profile unless it is drawn back towards the surface by evaporation and plant transpiration. The amount of water a soil can retain against the pull of gravity is called its water holding capacity (WHC). This property is close related to the number of very small micro-pores present in a soil due to the effects of capillarity action. The rate of water movement into the soil (infiltration) is influenced by; texture, physical condition (structure and tilth), along with the amount of vegetative cover on the soil surface. Coarse (sandy) soils allow rapid infiltration, but have less water storage ability, due to their generally large pore sizes. Fine textured soils have an abundance of micropores, allow them to retain a lot of water, but also causing a slow rate of water infiltration. Organic matter tends to increase the ability of all soils to retain water, and also increases infiltration rates of fine textured soils.

    The third important function: Soil performs one of its greatest functions; Decomposition of dead plants, animals, and organisms by soil flora and fauna (e.g., bacteria, fungi, and insects) transforming their remains into simpler mineral forms, which are then utilized by other living plants, animals, and microorganisms in their creation of new living tissues and soil humus. Many factors influence the rate of decomposition of organic materials in soil. Major determinants of the rate of decomposition include the soil physical environment, and the chemical make-up of the decomposing materials. The activity levels of decomposing organisms are greatly impacted by the amount of water and oxygen present, and by the soil temperature. The chemical makeup of a material, especially the amount of the element nitrogen present in it, has a major impact on the ‘digestibility’ of any material by soil organisms. More nitrogen in the material will usually result in a faster rate of decomposition.
    Through the processes of decomposition and humus formation, soils have the capacity to store great quantities of atmospheric carbon and essential plant nutrients. This biologically active carbon can remain in soil organic matter for decades or even centuries. This temporary storage of carbon in the organic matter of soils and biomass is termed carbon sequestration. Soil organic carbon has been identified as one of the major factors in maintaining the balance of the global carbon cycle. Land management practices that influence soil organic matter levels have been extensively studied, and are often cited as having the potential to impact the occurrence of global climate change.

    The fourth important function: Soil is teeming with living organisms of varied size. Ranging from large, easily visible plant roots and animals, to very small mites and insects, to microorganisms (e.g. bacteria and fungi.) Microorganisms are the primary decomposers of the soil, they perform much of the work of transforming and recycling old, dead materials into the raw materials needed for growth of new plants and organisms. For instance; an earthworm in its burrow excretes its waste (middens) on the soil surface, once deposited there it is further broken down by bacteria and other soil organisms. Organic materials in soil are consumed and digested repeatedly by different organisms on their path to becoming humus.
    Most living things on Earth require a few basic elements: air, food, water, and a place to live. The decomposers in soil have need of a suitable physical environment or ‘habitat’ to do their work. Water is necessary for the activities of all soil organisms, but they can exist in a dormant state for long periods when water is absent. Most living organisms are “aerobic” (requiring oxygen), including plant roots and microorganisms, however some have evolved to thrive when oxygen is absent (anaerobes). Greater soil porosity and a wide range of pore sizes (diameter) in the soil allows these organisms to “breathe” easier. Soil texture has a great influence on the available habitat for soil organisms. Finer soils have a greater number of small ’micro-pores’ that provide habitat for microorganisms like bacteria and fungi. In addition to the need for suitable habitat, all soil organisms require some type of organic material to use as an energy and carbon source, which is what they require as food. An abundant supply of fresh organic materials will ensure a robust population of soil organisms.

    The fifth important function: Soils are the base material for roads, homes, buildings, and other structures set upon them, however, the physical properties of different soil types vary greatly. The properties of concern in engineering and construction applications include: bearing strength, compressibility, consistency, shear strength, and shrink-swell potential. These engineering variables are influenced by the most basic soil physical properties such as texture, structure, clay mineral type, and water content. Landscaping applications range in scale from bridge and roadway construction around highway interchanges to courtyards and greenspaces around commercial sites to the grading and lawns of residential housing developments. In all these instances, both the physical and ecological functions of soils must be considered. Exposure of soil at a construction site creates potential for soil erosion by water, wind, or both. Eroded soil pollutes waterways and causes sedimentation of ponds and reservoirs.
     
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  3. Bryant RedHawk

    Bryant RedHawk Junior Member

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    Soil Quality, as a general concept, can be thought of as the ability of a soil to function, in either natural or managed ecosystems, to sustain plant and animal life, and maintain or enhance air and water quality.
    For agricultural ecosystems, we may consider Soil Quality as the ability of a soil to produce safe and nutritious crops in a sustained manner over the long-term, without impairing the resource base or harming the environment.
    Notice that this premise seems to be contrary to the currently accepted commercial agricultural model in the developed countries as well as those currently becoming developed countries.
    Machinery use is one of the catch 22’s of the modern agricultural model.
    Another is the relatively new “package” where seed is matched to herbicides and sold with discounts to entice farmers to purchase these products.

    Soil Quality has the potential for many different interpretations.
    Quality is dependent upon factors such as land use, soil management practices, ecosystem and environmental interactions, and the priorities of human societies.
    When considering Soil Quality in any specific case, it is necessary to identify the major issues of concern with respect to that soil’s function.
    Soil that is great for holding up buildings is not particularly good for raising any crops.
    Whatever definition of the term Soil Quality is deemed appropriate for a specific use, it should relate to the capacity of the soil to function effectively with regard to productivity; environmental quality; and plant, animal, and human health now and in the future.
    Since the majority of food and fiber needs of the human population are met by crops grown in managed agricultural ecosystems, the focus of government agencies is on those systems.
    However, the basic principles presented should be applicable to soils in other ecosystems, both natural and managed.

    Some soil properties can be relatively easy to observe, measure, and monitor over time:

    Soil properties used as indicators of soil quality.

    Physical
    Topsoil depth
    Texture and aggregation
    Aeration and infiltration
    Surface cover
    Compaction

    Chemical
    Organic matter content
    Salinity-electrical conductivity
    Acidity - alkalinity (pH)
    Nitrate nitrogen

    Biological
    Soil Respiration (CO2)
    Microbial activity/biomass
    Earthworm counts
    Plant vigor


    Major factors which lead to reductions in soil quality, land degradation, and soil erosion:

    • Mismanagement: Lands that are improperly managed (e.g., improper tillage) lose their topsoil.
    Either in large chunks during extreme erosive events, or little by little over an extended period of time, the soil disappears from the land resulting in reduced productivity and a degraded condition.

    • Salinization: Results from the accumulation of salts in improperly irrigated soils, most frequently in arid regions.

    • Overharvesting: Occurs on cultivated soils when repeated harvests are made from land without returning organic residues and mineral nutrients to the soil.

    • Contamination: Exposure of soil to toxic substances, as a result of industrial processes or chemical spills, can severely damage the ability of a soil to perform its ecosystem function.

    Cultural and environmental factors which enhance or degrade soil quality:

    Soil Quality Enhancing
    organic material additions
    plant growth
    cool, humid climate
    vegetative cover
    fibrous root systems of plants
    minimal tillage operations
    wildlife

    Soil Quality Degrading
    overharvesting
    bare fallow
    fire
    hot, arid climate
    exposed soil
    erosion
    intense tillage
    wildlife


    For plant growth, the topsoil is the richest and most valuable part of the soil.

    Topsoil formation is a very slow process (in nature, (we are developing methods that enhance the speed of natural topsoil production)), which makes it a non-renewable (within the current standard thinking), (but re-usable) resource in terms of human lifespans.
    Keeping the soil in place while it is used for construction or crops is one of the greatest challenges faced by engineers and land managers.
    Unfortunately the current engineering manifest does not take soil condition (other than what is best for their use) into account.
    Soil erosion losses are greatest when the soil surface is exposed to intense rainfall, resulting in gulley formation.
    Natural soil fertility is largely contained in the remains of formerly living things, also known as organic matter.
    Continuous removal of plant material for food or forage leads to gradual depletion of natural soil fertility.
     
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  4. Bryant RedHawk

    Bryant RedHawk Junior Member

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    Soil Orders
    Soil properties can vary greatly from one location to the next, even within distances of a few meters.
    These same soil properties can also exhibit similar characteristics over broad regional areas of like climate and vegetation.

    The most general level of classification in the USDA system of Soil Taxonomy is the Soil Order.
    All of the soils in the world can be assigned to one of 12 orders.
    By surveying soil properties of color, texture, and structure; thickness of horizons; parent materials; drainage characteristics; and landscape position, soil scientists have mapped and classified nearly the entire contiguous United States and much of the rest of the world.

    Soil Orders and General Descriptions
    Type Description
    Entisols Little, if any horizon development

    Inceptisols Beginning of horizon development

    Aridisols Soils located in arid climates

    Mollisols Soft, grassland soils

    Alfisols Deciduous forest soils

    Spodosols Acidic, coniferous forest soils

    Ultisols Extensively weathered soils

    Oxisols Extremely weathered, tropical soils

    Gelisols Soils containing permafrost

    Histosols Soils formed in organic material

    Andisols Soil formed in volcanic material

    Vertisols Shrinking and swelling clay soils

    Descriptions of the 12 soil orders

    Entisols are a very diverse group of soils with one thing in common, little profile (horizon) development.
    Includes the soils of unstable environments, such as floodplains, sand dunes, or those found on steep slopes.
    Entisols are commonly found at the site of recently deposited materials (e.g., alluvium), or in parent materials resistant to weathering (e.g. sand).
    Entisol soils also occur in areas where a very dry or cold climate limits soil profile development.
    Productivity potential of entisols varies widely, from very productive alluvial soils found on floodplains, to low fertility/productivity soils found on steep slopes or in sandy areas.

    Aridisols are dry soils with CaCO3 (lime) accumulations, common in desert regions.
    The extent of aridisol occurrence throughout the world is widespread, second in total ice-free land area only to the entisols.
    Extensive areas of aridisols occur in the major deserts of the world, as well as in southwestern north america , Australia , and many Middle Eastern locations.
    Aridisols are commonly light in color, and low in organic matter content. Lime and salt accumulations are common in the subsurface horizons.
    Some Aridisols have an argillic (clay accumulation) B horizon, likely formed during a period with a wetter climate.
    Water deficiency is the dominant characteristic of Aridisols with adequate moisture for plant growth present for no more than 90 days at a time.
    Crops cannot be grown in these soils without irrigation. Productivity of Aridisols is generally low, and there is potential for land degradation due to overgrazing by livestock.
    If irrigation water is available, Aridisols can be made productive through use of fertilizers and proper management.

    Alfisols are found in cool to hot humid areas, and in the semiarid tropics; they are formed mostly under forest vegetation, but also under grass savanna.
    Extensive areas of alfisols are found in the Mississippi and Ohio River valleys in the USA, through Central and Northern Europeash and cinders near or downwind from volcanic activity.
    Generally lacking in development, they are not extensively weathered, forming in deposits from geologically recent events.
    Usually of high natural fertility, they tend to accumulate organic matter readily and are of a ‘light’ nature (low bulk density) that is easily tilled.
    These soils generally have a high productivity potential.

    Inceptisols are soils in the beginning stages of soil profile development.
    The differences between horizons (layers) are just beginning to appear.
    Some color changes may be evident between the emerging horizons, and the beginnings of a B horizon may be seen with the accumulation of small amounts of clay, salts, and organic material.
    These soils show more profile development than entisols, but have not developed the horizons or properties that characterize other soil orders.
    Inceptisols are commonly found throughout the world, and are prominent in mountainous regions.
    The natural productivity of these soils varies widely, and is dependent upon clay and organic matter content, and other edaphic (plant-related) factors.

    Mollisols take their name from the Latin word mollis, meaning soft.
    These mineral soils have developed on grasslands, vegetation that has extensive fibrous root systems.
    The topsoil of mollisols is characteristically dark and rich with organic matter, giving it a lot of natural fertility.
    These soils are typically well saturated with basic cations (Ca2+, Mg2+, Na+, and K+) that are essential plant nutrients.
    These characteristics of mollisols place them among the most fertile soils found on Earth. Found in North America from Texas up to Saskatchewan, Canada.

    Spodosols commonly form in sandy parent materials under coniferous forest vegetation.
    As a consequence of their coarse texture, they have a high leaching potential.
    Spodosols are characterized by high acidity, and have a subsoil accumulation of organic matter, along with aluminum and iron oxides, called a spodic horizon.
    Typically low in natural fertility (basic cations, Ca2+, Mg2+, and K+) and high in soil acidity (H+, Al3+), these soils require extensive inputs of lime and fertilizers to be agriculturally productive.
    Spodosols are most commonly associated with a cool and wet climate, but also occur in warmer climes such as in Florida, USA. Large areas of spodosol are found in northern Europe, Russia, and northeastern North America.

    Oxisols are the most weathered of the 12 soil orders in the USDA soil classification system.
    They are composed of the most highly weathered tropical and subtropical soils, and are formed in hot, humid climates that receive a lot of rainfall.
    Oxisols are located primarily in equatorial regions.
    These soils are extensively leached, and the clay size particles are dominated by oxides of iron and aluminum, which are low in natural fertility (Ca2+, Mg2+, K+) and high in soil acidity (H+, Al3+).
    While oxisols are typically physically stable, with low shrink-swell properties and good erosion resistance, these soils require extensive inputs of lime and fertilizers to be agriculturally productive.

    Histosols are soils without permafrost that are predominately composed of organic materials in various stages of decomposition.
    They generally consist of at least half organic materials (by volume).
    They are usually saturated with water which creates anaerobic conditions and causes organic matter accumulation at rates faster than that of decomposition.
    Little soil profile development is present, due to their saturated and anaerobic condition, however layering of organic materials is common.
    Histosols can form in wetland areas of any climate where plants can grow such as bogs, marshes, and swamps, but are most commonly formed in cool climates.

    Vertisols are soils with a high content of clay minerals that shrink and swell as they change water content.
    The clay minerals adsorb water and increase in volume (swell) when wet and then shrink as they dry, forming large, deep cracks.
    Surface materials fall into these cracks and are incorporated into the lower horizons when the soil becomes wet again.
    As this process is repeated, the soil experiences a mixing of surface materials into the subsoil that promotes a more uniform soil profile.
    Vertisols are usually very dark in color, with widely variable organic matter content (1 – 6%).
    They typically form in Ca and Mg rich materials such as limestone, basalt, or in areas of topographic depressions that collect these elements leached from uplands.
    Vertisols are most commonly formed in warm, sub-humid or semi-arid climates, where the natural vegetation is predominantly grass, savanna, open forest, or desert shrub.
    Large areas of vertisols are found in Northeastern Africa, India, and Australia, with smaller areas scattered worldwide.

    There are color maps available online to see the Soil Orders by continent, just do a search for "Soil Orders by Continent"
     
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  5. 9anda1f

    9anda1f Administrator Staff Member

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    Nice work! Thank you! Water is such a necessary component to the breakdown of organic materials (leading to humus) ... we find in our dry climate that most of this natural composting takes place during the wetter months of late fall through early spring. Tree sticks left on the ground turn into bleached white things resembling old bones. Will be doing some further experiments with pit composting in an attempt to lengthen the active period of organic material breakdown.
     
  6. songbird

    songbird Senior Member

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    a refresher for me if i had a bit more time to read it. thanks, will get back to it. :)
    getting back the busy season.
     
  7. Bryant RedHawk

    Bryant RedHawk Junior Member

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    Soil Tests are performed from a basis of pH being the most important factor. As most all of us in the permaculture world know, this is a fallacy since plants and trees have the ability to change the pH of their immediate environment (the 5 mm surrounding each root will have the pH adjusted to the plant specific optimal environment, this is created by the use of exudates and is but one of the reasons plants create exudates the other primary reason is communication between the plant and the microbiome they grow in (bacteria, fungi, and other soil living organisms).

    Studies have shown that the gross application of just about any "amendment" creates an out of balance environment which the plants and microbiome organisms then have to work harder to readjust back to the proper levels, if they can. It could be thought of as creating a gluttony situation for the plants and micro critters. The end result is that "fat" or "obese" plants are created by the well meaning farmer who follows his soil test recommendations to the letter. This is not a good practice, for nutritionally rich plants, which are perfectly capable of messaging the biome for the nutrients they need at the time they need them. The accepted model of what happens is a permeable membrane for Na, if there are more ions on the outside of the membrane, they will move inside to create a balance of ions, if you already have the right number of Na ions inside, you will get a super saturation of Na, inside the membrane, which means other, more necessary ions can't move in where they are needed. It can even lead to plant poisoning.

    It is always best to err on the low side of any recommended amendments found in a soil test, that way you don't shift the balance a huge amount at any time.
     
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  8. Bryant RedHawk

    Bryant RedHawk Junior Member

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    My own current research is the complex interactions of the primary microbiome found in soils in Arkansas. I had to narrow it down to that area since it is easiest for me to go gather samples to test. I am running chemical composition tests and microscopic observations of the bacteria, fungal hyphae, nematode and other organisms in each sample. If there is interest in such data, let me know and I will be happy to share the findings before I submit my DT.
     

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