California Soil Ecology - What is Living Soil?
Understanding Sustainable Soil Structure Management and Fertility
What is living soil? It is the key to sustainable soil structure management and fertility! A primary goal of sustainable living on a small farm is obviously to produce an abundance of safe nutritious food – enough to meet your needs as well as a surplus to barter with others or value add for addition income.
To achieve this goal, you must first understand how soils work, then get to know your own soil and take appropriate steps to optimize its fertility and productivity.
What is Living Soil?
The goal of sustainable soil management is living soil. So what is living soil? It is perhaps easiest to start by considering situations where the soil ecosystem is dead.
Hydroponic systems have essentially dead soils – plants grow in soil media that merely provide the roots with something to hold onto while being loose enough to allow air to get to them.
Nutritional needs of hydroponic plants are met not from the “soil”, but from fertilizers dissolved into their irrigation water. Similar soluble fertilizers are also used in conventional farming systems whose soils are often only barely alive due to chemical use.
The plants are forced to intake the soluble nutrients whenever they drink, and as a result grow rapidly and produce hefty crops. The farmer gets paid, the consumer gets attractive looking food, and all seems well. So what’s wrong with that?
Dead Soil - Farming Outcomes
Here are some of the problems of plants grown this way:
• Poor vitality:
Force-fed plants are inherently weak and need protection from pests, diseases and weeds via chemicals and poisons.
The soluble fertilizers leach away and contaminate rivers and streams causing eutrophication and algal blooms.
• Low nutritional value:
Force-fed plants have low nutritional value, and taste like it too!
• Low drought tolerance:
Force-fed plants are highly dependent on moisture to maintain a comfortable dilution of the fertilizer salts dissolved in their cells. So the plant dies as soon as soils start to dry out.
• Climate unfriendly:
Agricultural crop chemicals and fertilizers require a large amount of energy to produce, contributing to the greenhouse effect.
So...What is Living Soil?
Living soil on the other hand is full of life. What is living soil but a functional ecosystem of soil critters and microbes that interact with plants to naturally promote healthy growth. For those of us aspiring to sustainable living, eating vibrant plants and animals is a cornerstone to sustainable health.
Living Soil – Farming Outcomes
The benefits of living soil are many:
Produce delicious, nutrient-rich foods.
• High vitality:
Naturally grown plants are inherently strong and need less protection, allowing organic food production methods to be used.
• Drought tolerant:
As their food is in colloidal states rather than being soluble, naturally grown plants only feed when they want to, are not overloaded with chemical salts, and can continue to grow under drier conditions.
• Low pollution:
Fertilizers used are not soluble so stay in the soil where they are needed rather than leaching away and causing pollution.
• Greenhouse friendly:
Does not require energy intensive inputs of agricultural crop chemicals and fertilizers.
What Lives in Soil?
Because it’s hard to make a dollar from all the amazing ways that soil life enhances the vitality and productivity of the entire soil/plant system, there has been very little study into soil biology. However we do know that a diverse range of creatures and microbes contribute to what is living soil including:
• Macro-fauna such as earthworms, slugs, nematodes, termites and earth-mites
• Micro-flora including a range of varieties of soil fungi, molds, yeasts and algae
• Micro-fauna including many types of bacteria and protozoa in soil
• Other microbes such as actinomycetes which are in between bacteria and algae and break down tough organic material even under tough conditions
The weight of all these critters in a healthy living soil combined is as much as that of the livestock that grazes above the surface! They are integral to a healthy soil system that supports healthy plant growth.
What is living soil contributing to productivity?
Soil life works in beneficial relationship to plants, both directly and indirectly. Consider these examples:
• Worms are good for soil:
Earthworms benefit soil by bringing surface nutrient materials into the soil where they can be accessed to feed the soil ecosystem.
They make use of low grade wastes and excrete and recycle them as nutrient rich worm castings. These castings also have a high capacity to bind and hold soil nutrients in a colloidal (non-soluble) state.
The slime-lined tunnels they make create channels for the movement of air and water through the soil.
• Soil fungi are amazing:
Have you ever lifted up a rock and seen a delicate network of filaments and threads lacing the soil underneath? These are the hyphae of soil fungi. Some types of fungi live symbiotically with plants.
They attach to plant roots and take in sugars that plants are able to make from photosynthesis of sunlight.
In return the fungi reach out with their long hyphae and scout the surrounding area for nutrients that the plant needs. It’s amazing that the presence of symbiotic fungi can increase the availability to plants of some nutrients by nine-fold!
• Soil bacteria are tops:
There are many types of bacteria in soil that perform life enhancing and unique services that benefit plants. One that is well-known is nitrogen fixation.
Nitrogen (N) fixing bacteria have the ability to grab and make use of N from the very air. Some species have a symbiotic relationship with particular plants where they make this N available to those plants in little nodes that form on the plants’ roots especially for this purpose.
• Soil algae are essential:
Soil algae are capable of photosynthesis. So like plants, they can convert sunlight into carbohydrates and sugars. They have an important role to play in working symbiotically with fungi to form a skin of lichen to protect soils that are too degraded to support higher plant life.
• Soil microbe complexes are cool:
In addition, complexes of soil microbes work on grosser rock and mineral complexes to break it down so that it becomes available as essential minerals to the wider soil/plant ecosystem. In a similar way they also break down gross organic materials and convert them to useful nutrients.
These complexes build up the humus and colloidal organic material in the soil and hold soil particles together in crumbs that provide plant accessible nutrients and create pores for the penetration of water and air into the soil.
• Soil life adds life:
The only reason existence can resist the universal trend towards disorder and disassembly (entropy) is because of life. Life re-uses, recycles and restores itself from the spent disarray of dead matter.
In soil this is particularly striking. The life in soil makes use of dead organic material and exhaled atmospheric gases to rebuild itself. It deposits the results into a bank that enriches the soil.
The action of soil organisms in living soil under ideal conditions is to convert organic wastes into humus. Humus provides good structure and available plant nutrients to soils. Humus is dark brown so soil color is a good indicator of its organic matter content. High humus, dark soils have:
• High fertility
• Low erosion potential
• High available Nitrogen
• Good aeration
Because soil life activity tends to be concentrated in the top layer of the soil profile, soil is usually darkest at the surface, becoming progressively lighter with depth.
You can check on the balance of the account by measuring the amount of organic matter in your soil. Ideally the soil is 3% or more organic material.
The organic matter has several functions: acting as a buffer to prevent changes in pH; absorbing and retaining moisture in the soil; and holding onto free nutrients, that might otherwise be washed out of the system, until plants need them (“soil cation exchange capacity”).
What About Harmful Soil Life?
While normally only a very small part of soil life, harmful varieties of fungi, nematodes and macro-fauna may proliferate and cause problems when the soil system is stressed and out of balance.
Meeting the Needs of Soil Life
Apart from very specialized creatures, most life on Earth - from bacteria to humans - has these same basic needs in common:
Water is the basis to all life on Earth. The soil ecosystem will only function at peak productivity if adequate moisture is available to support cell function within its biota.
Because of the integral relationship between plant health and soil health, when you feed the soil you feed the plants. So what does soil life need? The same nutrients that we need – proteins, carbohydrates and essential minerals and trace nutrients.
A rarely appreciated fact is that both plants and soil critters need air! Well structured soils provide this air via soil pores that exist around small clumps of soil held together by soil life. Such soils will have a crumb-like feel to them. Sustainable soil structure management promotes soil life as the key to maintaining healthy soil structure.
All life has an acceptable range of pH and temperature within which constitutes a comfortable environment in which they can function at their optimum. If conditions become too hot or cold, too acidic or alkaline, life energy is compromised or if extreme, extinguished. This is the basis of the disinfecting qualities of strongly alkaline substances such as bleach, designed to kill life.
Knowing what is living soil’s ideal conditions and ensuring they are met allows you to optimize the productivity of your small farm system.
Checking Out Your Soil
• Soil organic matter
• Types of Soil
• Soil Structure (infiltration test)
• Soil Profile
When it comes to farm production potential, soils ain’t soils. There are a wide range of soil types. Why is soil so important? Because each differs in its intrinsic ability to provide what is soil life, and thus plants’, basic needs.
Types Of Soil
All soil is a combination in varying proportion of three main types of soil particle: sand, clay and silt. The amount of sand, silt, and clay affects these important soil properties:
• Ability of the soil to store water and nutrients
• Speed that water will infiltrate and flow through the soil
• How easily air can infiltrate the soil
• What kind of plants the soil will grow well in the soil
• How deep plant roots can extend
How to Recognize Different Types of Soil
Want to know how to tell the difference between them? So, time to get your hands dirty!
Go out there and get a few samples (about a coffee cup full) from the top 4 to 6 inches of your soil(s).
It is also wise to get to know your soil the way your plants will – down to the rooting depth. So use a shovel or post-hole digger to get down and dirty at expose at least 1 to 2 ft of the soil profile. You will notice definite layers to the soil profile that change with depth, each with its own color and texture.
Soil Texture - How does your soil feel?
You can glean much about your soil’s composition by how its texture feels in your hands when it is wet or dry. So grab some and have a feel!
Sand is the largest particle in the soil, varying in size from fine sand (0.05mm) up to coarse sand (2.0 mm).
• Because sand granules have sharp edges, when you rub it, it feels rough and gritty whether wet or dry.
• When you add some water to it and try to form it into a ball or a sausage, it falls apart.
The size of silt soil particles is in between sand and clay, between 0.002 and 0.05 mm.
• When you rub it, it feels smooth and powdery. When moistened it feels smooth but not sticky.
• When you add some water to it and try to form it into a ball it holds together, but will break into sections if you try to roll it into a thin sausage
Clay has the smallest soil particle being less than 0.002 mm in size.
• When you rub dry clay it feels smooth. When moistened it feels smooth but sticky.
• When moist, clay can be molded, with a bit of pressure, into stable balls or rolled into a long sausage that holds together even if you pick it up at one end.
Loam is a combination of sand, silt and clay particles so has texture properties of each.
• Loam soil feels smooth, but partially gritty.
• When wet it is sticky and readily forms a ball, but the ball crumbles easily.
Jar Test for Telling Soil Type
• Half fill a large jar with a sample of your soil.
• Make up to almost full with clean water.
• Put on a tight fitting lid and shake the jar until you have broken up any soil clods and lumps into suspension.
• Leave it undisturbed to settle for 24 hours or so then come back and check it out.
The different soil particle types – silt, sand and clay – will have settled out into distinct layers. You will gain an excellent indication of your soil type and its properties simply by noting the relative proportion of each type of particle in your soil!
Properties of each soil type
Soils high in sand content are described as “light” soils. Sand has:
• Poor ability to store nutrients
• Excellent water infiltration so is usually well drained, unless it is water repellent or compacted
• Poor water holding capacity so requires more frequent watering
• Good aeration (lots of large air spaces around the sand granules) unless compacted
• Good ability to store nutrients
• Good water infiltration unless compacted
• Good water holding capacity
• Good aeration unless compacted
Soils high in clay content are described as “heavy” or “tight” soils. Clay soils have:
• Excellent ability to store nutrients.
• Poor water infiltration – water will tend to pool and take a long time to drain away. Poor drainage suffocates susceptible plants because the water stops air from penetrating the soil. Clay makes good dam building material though!
• Excellent water holding capacity, but water is so tightly held it is not easily accessed by plants
• Poor aeration
Soil Structure & Soil Testing
It is due to the action of soil life that structure develops in a soil. Soil structure is the clumping together of soil particles into aggregates by humus. The clumps hold nutrients and retain moisture, while the space around the clumps allow air and water to percolate through the soil.
A well structured soil will be fertile with good drainage, and will have a crumb-like texture.
Poor soil structure occurs commonly in low organic matter sands - the soil pores around the sand particles are large so lose water and do not hold nutrients.
It also occurs in non-structure clays where the soil pores around the tiny clay particles are so tight that it is hard for water or air to penetrate them.
Both can be improved by the addition of organic matter (e.g. compost or mulch) forked into the top 30 cm.
Living soil will convert this organic matter into humus which will then allow aggregates to form, and good soil structure to be developed.
Sustainable soil structure management similarly depends of feeding and looking after soil life so that it can do its job of building good soil structure and fertility.
The first commandment of sustainable small farm living is “know thy soils”. And the only reliable way to gain the information you need to strategically build the productivity of your soils is by having the right soil analysis done.
Many soil testing laboratories are allied with chemical fertilizer manufacturers. So commonly they only look at aspects of soil nutrition that can be remedied by the application of mainstream fertilizers and amendments such as lime, superphosphate and NPK (combination of nitrogen, phosphorus and potassium). While following their recommendations will normally improve soil productivity, it does not optimize it!
Soil optimization is an exact science requiring more complex considerations.
The Albrecht Method of Soil Testing
Dr William Albrecht was a brilliant scientist who, in aspiring from a young age to serve humanity at the highest possible degree, devoted his career to soil science.
Why soil science? Because he was the first scientist to recognize that all our nutrition and thus health comes from soil.
Albrecht who was Professor of Soils at the University of Missouri, conducted thousands of soil experiments between 1918 and 1974. Over a lifetime of research, he developed the means to perfect the chemical make-up of soil.Today, sustainable organic farming utilizes the “Albrecht System” of soil management. Soil Nutrition
Healthy crops, animals and humans depend utterly on soil fertility, which in turn depends on adequate and balanced amounts of organic material, major elements and trace minerals. Soil pH
Soil pH is conventionally considered as a measure of the activity of hydrogen ions (H+) in a solution containing soil. The soil pH scale ranges theoretically from 0 (extremely acidic) to 14 (extremely alkaline), but these extremes are rarely found in reality. A reading of 7 is neither acid nor alkaline, but “neutral”.
Why is soil pH important?
Because it not only affects the physical comfort of soil life, but also the availability of soil nutrients for plants and soil life alike.
As the chart shows, at a slightly acidic pH (5.5 to 6.5), the availability of most soil minerals is optimal. Alkaline or acid soil types may favor the odd specially adapted species of plant, but most types of plants will do best in this mildly acidic pH range.
[Effect of alkaline or acid soil types on mineral availability]
Because of a simplistic view of soil pH, pH correction recommendations usually dictate the addition of lime to alkalinize acidic soils, or of sulfur to acidify alkaline soils.
However, Albrecht taught that soil pH is not merely measuring its hydrogen ions. In fact, four major cations (positively charged mineral elements) contribute to soil pH: calcium (Ca++), magnesium (Mg++), potassium (K+) and sodium (Na+).
He also found that these cations must be in balance with each other.
If these major cations are not in balanced proportions with each other:
• Soil structure is compromised.
The most important cations affecting soil structure are magnesium and calcium. A soil with excessive magnesium compared with calcium will be sticky when wet (walk on it and you will develop elevator shoes!) and tend to be too tight and crack when dry. A soil with excessive calcium over magnesium will tend to be too open, and apt to dry out rapidly. So sustainable soil structure management begins with balancing these cations.
• Dominant elements suppress the availability of those in shorter supply.
Even with a good supply of calcium, for example, soil life and plants may still suffer from calcium deficiency if magnesium is relatively over-abundant in the soil.
Albrecht Soil Testing
The Albrecht system comprises strategically developed soil testing procedures to measure and prescribe the correct chemistry to achieve your soil’s real potential.
Albrecht-educated soil laboratories provide soil amendment recommendations aimed at bringing a soil to its optimum state in terms of structure, fertility and ability to grow nutritious, healthy food.
Collecting Your Soil Sample for Testing
It is pretty simple to collect a soil sample, but care must be taken to ensure it will give you the information you are looking for.
All the soil sampling equipment you will need is a clean, flat, square ended spade and a clean dry bucket. Call the Lab ahead of time and they will supply you with a sample bag for the final sample which will show how much soil should be in it. Around 300 grams is about right.
Depth of Soil to Sample
This depends on what you want to grow! For productive vegetables, vines and orchards you’ll need to collect the top 15cm (6 inches). If you are only growing pasture, the top 10cm (4 inches) will be sufficient.
Where to Sample
If you have significant areas of distinctly different soil types (for example, one of clay loam and another of loamy sand) you will need to sample them separately.
Your sample should be representative of the area you want to optimize. I achieve this by zig-zagging across the area and taking several (say 20) samples. Then mix these thoroughly together forming a batched sample from which your sample for testing can be taken.
Where Not to Sample
Avoid areas that are not representative of the average condition of your soil. For example, places where metal scrap has been left to rust, animals have decomposed, fertilizer has been stored, stock tends to congregate, or that are close to old water-tanks, troughs, buildings, roads, gateways, fencelines or burn-off.
Soil Test Results
Your laboratory will analyze your sample and measure the following:
• Cation Exchange Capacity (Total Exchange Capacity). This is an indicator of the soil’s ability to store nutrients.
• Organic matter content
• Content of Macro-Nutrients: Nitrogen, Sulfur, Phosphates.
• Phosphate Recovery %: Phosphate tends to get “locked up” in some soils, so not all phosphate applied to soil will become available to plants. This affects the amount of phosphate that needs to be added.
• Base Saturation Percentages: Measure the content of the major cations relative to each other.
• Major Cations: Calcium, Magnesium, Potassium and Sodium.
• Trace Elements: Boron, Iron, Manganese, Copper, Zinc.
• Salinity (electrical conductivity)
Using Organic Soil Amendments
Your laboratory will do the sums for you based on your soil test results and come up with a tailored prescription of minerals needed to bring its chemical composition up to optimum balance.
Recommended amendments for organically balancing soils are as follows:
Cation Exchange Capacity:
Both clay and humus have excellent cation exchange capacity (CEC). Soils with low CEC can be improved by the addition of or organic matter (which will then be converted to humus by the activity of soil life) or clay. Shallow clay subsoils can be pulled up to improve surface sands using specially designed rippers.
Organic Matter Content:
Soil organic matter can be increased by many means, from adding a few inches of compost, manure or worm castings, to growing green manure crops slashed before seed set. Both should be worked into the top soil using a scarifier or hand hoe.
Mineral amendments to correct deficiencies and pH:
These can be cast by hand out of a bucket or using a special mechanical spreader across the property, taking care to distribute the correct amount per unit area as prescribed by your laboratory. It is helpful to mark areas of set size off using stakes or surveyor’s tape. Ideally, they should be scarified lightly into the soil afterwards. The best time is just after the first rains when the soil is moist and soft, but not sopping wet.
Our soil analysis resulted in the following recommendations:
Base Saturation Percentages
Correct Base Saturation Balance of Major Cations and pH by adding:
• 2.5 tonnes of Dolomite (Calcium Magnesium Carbonate) per hectare, and
• 2.0 tonnes of Lime (Calcium Carbonate) per hectare. Note that lime sands vary in quality according to fineness (the finer or smaller the grain size the better) and neutralizing capacity (effect on pH). Don’t use burnt or builder’s lime as it is too caustic to soil biota.
Our paddock is too rocky to scarify so we are relying on worms to incorporate our minerals for us. Adding lime at the beginning of the wet season really stimulates earthworm activity and they do a fine job of pulling it into the soil and mixing it through the profile.
• 400 kg/hectare of Sulfate of Potash (Potassium)
• Phosphate - Our soil is low in phosphorus so we need to add 750 kg of soft rock phosphate (not superphosphate which has been acid treated so is toxic to soil life, is too soluble so is easily washed away, and often contains toxic heavy metals such as cadmium)
• Nitrogen – We will be adding nitrogen by sowing clovers, lupins, lucerne and nitrogen-fixing perennial plants into the system (wattles, tagasaste, etc). Correcting pH will encourage their growth by creating good conditions for N fixing bacteria. Clovers, for example, can add 200 kg of nitrogen per hectare per year to the soil under dryland conditions.
• Potassium – see above.
Our soil is boron deficient so we will also be supplementing its nutrition with an organic stabilized boron preparation at 25 kg/hectare.
In Australia, small farmers on the east coast can source minerals from Nutri-Tech; on the west coast a good supplier is Optima Agriculture.
Other Soil Amendments
Soil guru Arden Anderson recommends adding sugar to soil in carefully calculated amounts to boost the activity of soil microbes. The sugar can be in the form of solutions of raw or white sugar or molasses.
His clients have reported very good results with annual additions of 25 litres of molasses per hectare (10 litres an acre), OR sugar at 22kg/hectare (9 kg/acre).
Be aware that exceeding these recommendations can lead to adverse effects.
Humates and Humic Acid
Research has shown that humates restore the soil vitality of the soil, increase its water holding capacity, and improve the availability of fertilizers.
While it is possible to source bulk soil humate supplements, the best long term strategy for boosting soil humates is to encourage earthworm activity, since their feces are a rich source.
The biodynamic preparation 500 is basically a humus mixture. It is stirred in an exact method with water and distributed on the land at astrologically auspicious times.
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