Healthy soil and sustainable growing

[Dieter Brand <diebrand@yahoo.com>]

Excellent article, well worth reading.  A comprehensive and easy to

understand resume of everything one needs to know about the

advantages of organic no-till gardening.

 

Dieter Brand

TradingPostPaul <tradingpost@riseup.net> wrote:

> For those who may have missed it, here's Harvey's previous piece on
> building soil, in Mother's April/May 2007.
> http://www.motherearthnews.com/Homesteading-and-Self-Reliance/2007-04-01/Bet
> ter-Garden-Soil.aspx
>
> paul tradingpost@lobo.net
> ------------------------------------------
>
> 21st Century Homesteading: Build Better Garden Soil
> By Harvey Ussery
>
> Caring for the soil is the key to growing more of our own food
>
> Soil is the key to health, both for ourselves and for the animals and
> plants we depend on. But
>  soil “in good heart,” as farmers used to say,
> is not something we can take for granted. For gardeners and farmers, caring
> for the soil must always be our first priority, and the process of building
> soil fertility is vast and complex.
>
> The best question to ask is not “What is the best soil care?” but
> “What is the best soil care for this particular piece of ground?” Over
> the seasons, the soil itself becomes our teacher and shows us which
> practices lead to beneficial changes.
>
> Let’s begin with this intriguing question: Why is it that in natural soil
> ecologies, soil fertility tends to accumulate spontaneously over time,
> while human agriculture often leads to drastic declines in soil quality?
> Whether we look at prairies, bogs or forests, we find that topsoil tends to
> deepen and become more fertile over time. Why are humans more likely to
> destroy than to build soil quality, when natural systems operating on their
> own produce the
>  opposite result?
>
> One implication is obvious: The key to soil management is imitating natural
> systems. But perhaps the best answer to this riddle is that topsoil is
> alive, and any approach to agriculture that treats it as an inert substance
> is almost certain to be destructive.
>
> WHAT IS TOPSOIL?
>
> Topsoil is formed from tiny particles weathered or worn from their parent
> materials (rock, of various types). Both the chemical composition of the
> parent material and the average particle size help determine fundamental
> characteristics of soil — whether it is acid, alkaline or neutral; and
> whether it is sand (large particle size) or clay (extremely small particle
> size). But a layer of small rock particles is not “soil,” and it is not
> capable of growing a crop.
>
> Healthy topsoil also consists of a complex community of living creatures,
> and each class of organisms has its own strategies for feeding itself,
> adapting to
>  environmental conditions and coexisting with its neighbors. Any
> practice that destroys some or all of those classes of organisms is likely
> to reduce soil fertility.
>
> The number of living organisms in healthy topsoil is enormous: It has been
> estimated, for example, that the total biomass of organisms in a prairie
> soil exceeds 15 tons per acre, with the weight of the bacteria alone —
> invisible to the eye—totaling 13 tons! A single teaspoon of that soil may
> contain 600 to 800 million individual bacteria from a possible 10,000
> species; several miles of fungal hyphae; 10,000 individual protozoa; and 20
> to 30 beneficial nematodes from a possible 100 species.
>
> Living organisms in the soil include bacteria, fungi, protozoa (single-cell
> animals), nematodes (minuscule non-segmented worms), arthropods (insects,
> spiders, mites and centipedes — from microscopic to several inches long),
> earthworms, and larger organisms such as moles, voles
>  and even gophers,
> which have their role to play in recycling nutrients and maintaining good
> soil structure.
>
> THE ROLE OF ORGANIC MATTER
>
> Organic matter is constantly being produced in and over the topsoil —
> fallen leaves, dead plants and animals, roots shed by living plants, and
> droppings of passing animals. Different classes of soil organisms
> “specialize” in breaking down different sorts of organic matter in
> accordance with the natural principle that every creature’s “waste”
> is a priceless resource for another, and they pass their own wastes on to
> other members of the soil community.
>
> The energy represented by the original organic material is passed from one
> level of the soil food web to another, rather than being lost from the
> system. The energy of sunlight is constantly being added at the other end
> of the equation through photosynthesis, so if all nutrients are re-captured
> by soil organisms, the result has to be
>  added fertility.
>
> For example, when fresh green material is added — say in the form of crop
> residues, or green cover crops cut and used as mulch — it is bacteria
> that take the lead in breaking them down. Nematodes, protozoa and tiny
> arthropods feed on the bacteria, and are fed on in turn by larger
> arthropods and nematodes. Earthworms feed on the bacteria, as well as
> leaves and other organic matter, converting it all to castings rich in
> minerals and other nutrients in forms easy for plant roots to take up, and
> conducive to good soil structure. In the meantime, soil fungi colonize and
> feed on the denser plant tissues such as stems and leaf veins, as well as
> other more carbon-dense organic materials such as leaf mulches.
>
> Dead organic material is not the only source of food for soil-dwelling
> species. Roots of living plants form cooperative, mutually beneficial
> associations with various soil organisms. Some plants, including beets
>  and
> spinach, form such associations with bacteria; others, including tomatoes,
> potatoes and corn, with mychorrhizal fungi. In both cases, the plant
> creates complex sugars and other nutrients in its leaves, then releases
> them through its roots to feed its “buddies” in the soil. In exchange,
> the mychorrizae or bacteria provide nitrogen, enzymes, minerals and other
> nutrients to the roots in forms easy for them to absorb.
>
> These are simple sketches of complex relationships and food exchange. The
> end result of the process is humus, the final residue of the parent organic
> materials, now visible only as a darkening of the soil. The microscopic
> humus particles are no longer a source of food for soil organisms, but they
> help with water retention, bond with nutrients in the soil and pass them on
> to plant roots, and bind carbon into the soil. Many soil organisms also
> help “glue” soil particles together into larger aggregate
>  particles,
> increasing the size of pore spaces between particles, bringing more air to
> the soil (most soil organisms need oxygen to thrive) and increasing water
> flow down into the soil (reducing chance of runoff and erosion in heavy
> rains).
>
> Some soil organisms are pathogens, but with a diverse mix of species, they
> are usually controlled by other organisms in the system, which feed on the
> disease-causing organisms, out-compete them, or otherwise inhibit them.
> Simply put: Diversity of soil organisms is key to plant health.
>
> STRATEGIES FOR MANAGING SOIL
>
> Most of us have grown up thinking that soil fertility revolves around the
> question of what we need to buy and add to soil. We sometimes use soil
> tests to guide us in making the proper purchases. When we begin working
> with a piece of ground, especially if it has been abused, there may be
> additions we need to make. Be cautious about soil tests, however, because
> different
>  laboratories use different procedures, report results differently
> and adopt different approaches to interpreting the results.
>
> For example, I remember how confused I was by test results I used to get
> from my local extension service: They always noted that both phosphorus and
> potassium were “very high” — and then went on to recommend
> application of chemical fertilizers containing 10 percent of each. Later, I
> worked with a soil consultant (a student of pioneering soil scientist
> William Albrecht), who also noted the high levels of phosphorus and
> potassium, but recommended no fertilizer application.
>
> Indeed, he pointed out that it would be easy for my soil to rise to
> dangerously excessive levels of phosphorus if I wasn’t careful with
> certain organic matter applications, such as manures. Since most soil
> analyses focus so much on crop needs for nitrogen, imagine my surprise when
> he also recommended no added nitrogen. When I asked
>  about that, he replied
> dismissively, “Oh, with organic matter at the level you have, you don’t
> need any added nitrogen, except maybe a little for really heavy feeders
> like corn.”
>
> By all means, find and work with a competent soil consultant if you feel
> your soil has serious deficiencies or special needs. But your main focus
> should not be what purchased inputs you need to add to your soil, but on
> strategies to maximize the diversity, health and population densities of
> soil organisms.
>
> Three agricultural practices in particular are injurious to soil life:
>
> Monoculture. The growing of a single species on vast tracts reduces
> diversity of soil life.
>
> Use of harsh chemicals. Many chemicals — whether intended to fertilize
> crops, suppress disease, or kill insects and weeds — also destroy
> populations of soil organisms.
>
> Excessive tillage. Frequent tillage of soil disrupts soil life and robs it
> of its carbon (organic
>  matter) reserves.
>
> The alternative to such destructive practices is to imitate natural soil
> ecologies, which will:
>
> Take advantage of the diversity and population densities of soil organisms.
> While homesteaders are unlikely to practice monoculture — to grow nothing
> but carrots, for example — we should constantly find ways to “mix it
> up” in how we manage our soil. Crops of different families should rotate
> over the available ground in succeeding seasons. Diverse sources of organic
> matter should be used — composts, mulches, cover crops, etc.
>
> Feed the soil using sources of fertility grown on the homestead or close
> by. Deep-rooted cover and fertility crops can “mine” minerals from the
> deep subsoil and make them available to more shallow-rooted plants.
> Nitrogen-fixing legumes (clovers, alfalfa, beans and peas) can boost
> nitrogen for heavier-feeding crops. Recycle autumn leaves and crop residues
> by composting or using them as
>  mulches. Manures and mulching materials may
> be available from nearby farms. If a soil test does indicate the need to
> add minerals, use slow-release rock powders, such as greensand or colloidal
> rock phosphate, rather than highly soluble chemical fertilizers, which
> quickly leach into groundwater.
>
> Protect and improve soil structure. Plant in wide beds and don’t compact
> the soil by walking in the growing spaces. Keep the soil constantly
> covered—by closely-planted crop plants, cover crops or mulches. Addition
> of lime to most clay soils can help “flocculate” the almost microscopic
> soil particles into aggregate clumps, resulting in a looser, more open soil
> structure with better air and water penetration. When tight soil must be
> loosened, do it with a broadfork rather than a power tiller or even a
> spading fork to avoid inverting soil layers.
>
> THE LONG-TERM EFFECTS OF TILLAGE
>
> Many farmers, gardeners and homesteaders avoid
>  monoculture and harsh
> synthetic chemicals. However, many people committed to sustainable
> agriculture unknowingly till the soil in ways that inhibit long-term soil
> improvement.
>
> Tillage of soil releases a flush of nutrients, which can give an impressive
> initial boost to crop growth. But this surge of available nutrients results
> mostly from the death of large numbers of soil organisms, whose biomass
> decomposes rapidly into the soil. These nutrients tend to be in soluble and
> volatile forms, and if not taken up immediately by plant roots, are leached
> to groundwater or outgassed to the atmosphere. In the meantime, life cycles
> of many soil species are disrupted — fungal threads are broken, and
> earthworm burrows are destroyed — and it can be some time before their
> populations recover. If the next tillage occurs before they have done so,
> we have started a cycle which degrades the health and diversity of the soil
> food web.
>
> One of
>  the worst effects of excess tillage is the loss of carbon bound in
> the soil in the form of humus. Oxygen is necessary to soil life, which is a
> major reason we work to improve aeration in soil through creation of
> looser, more open “pore structure.” Excessive exposure of the soil to
> oxygen, however, as occurs in heavy tillage, leads to oxidation of the
> carbon content and its loss to the atmosphere as carbon dioxide (CO²).
> Not only is fertility — which is so dependent on humus content —
> impaired, but high-tillage agriculture is a major, and growing, cause of
> accumulation of CO², a greenhouse gas, in the atmosphere.
>
> The amounts of carbon involved are not trivial: Every 1 percent increase of
> carbon sequestered in a garden’s soil is estimated to be equivalent to
> the weight of all the carbon in the atmosphere above that garden, right out
> to the vacuum of space. By reducing tillage while adding all the organic
> matter we can, we reverse
>  CO² emission: Carbon is bound up in soil in the
> form of humus. The solution to climate change begins in your back yard.
>
> — In the next issue, Harvey Ussery will discuss how to get started with
> these three soil management techniques.
>
>
>
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