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The Importance of Soil Biology for Biodynamic Pasture Management

By Peter Bacchus

To grow healthy plants and animals and high-quality food products, you need fertile soil. Soil fertility in turn is related to the growth and reproduction of soil organisms and to the plants that grow in the soil. In due process this affects the health, well-being and fertility of the animals and humans who live as a result of the plants that grow in the soil.

We often do not recognize that soil fertility depends on the carbon cycle, which starts with photosynthesis in plant leaves and the absorption of light and carbon and other elements from the air into the plant. The carbon taken in from the air by plants and transformed into sugars is the basis of the carbon cycle, which maintains life in the soil by providing food for soil organisms.

The elements that come from the air in gaseous form can make up to 80 percent of solid plant tissue. And up to 90 percent of a plant is carbon and oxygen, two elements that are not measured in many plant tests. What is below ground helps make it happen.

One of the most often overlooked aspects in our farming is soil biology.

Soil organisms are the facilitators of mineral activity in the soil. They bring about a natural movement of minerals through incorporating them in their bodies. These organisms secrete digestive enzymes into the soil that enable the organisms to absorb the minerals as food. When the organisms die, the minerals are released in a form that plant roots can easily take up.

Tree roots in soil
Soil bacteria need sugars that they get from root exudates.

The payment these organisms exact for doing this work is a requirement for the right living conditions and some nutrition. And we can help achieve these requirements.

The organisms need air and moisture — but not too wet or too dry. They work best in a particular temperature range and, similar to humans, need food to their liking.

Not only do they need organic matter, they need a specific range of mineral nutrients. They can’t hop in the car or bus and go to the supermarket and pharmacy — they depend on us and our animals to deliver the goods.

The bacteria need sugars that they get from root exudates. Some of the sap that carries the sugars created by photosynthesis down to the roots is exuded into the soil.

As sunlight enables the photosynthesis through which sugars are made by plants, the soil organisms are fed indirectly by sunlight.

The mineral balance and health of the plant affects the quality of sugars exuded from plant roots.

For example, the element magnesium is needed by the plant to assist this photosynthesis process, and other elements, such as boron, assist the plant to move the sugars down to the roots and the soil nutrients up into the plant.

Animals and humans should obtain what they need from plants, and these plants should obtain what they need from the soil, air and light, rather than feeding minerals directly to animals and humans.

cows on pasture

When we try to take short cuts to speed things up, trouble may lurk and it often ends up being the long way round as well as the wrong way round. In this circle of life there are no free lunches and everything has to work for its living. Human intervention is part of this cycle and to get our “lunch” we need to do our bit with sensitivity and understanding.

Our first commandment for farmers, as in medicine, should be, “do no harm.”


Energy Cycles & The Soil Food Web

Sunshine begins the energy cycle and enables the plant to form sugars, taking carbon and oxygen from the air and hydrogen from the water.

Carbon, hydrogen and oxygen are the main constituents of sugar. The plant shares some of the sugars with the roots, mycorrhizal fungi and soil bacteria.

Sunlight on corn leaves
Sunshine begins the energy cycle.

Most beneficial soil organisms are aerobic, breathing nitrogen and oxygen from the air that contributes to the protein they build.

Soil organisms feed other organisms of different species in a continuous cycle described by Dr. Elaine Ingham in the Soil Biology Primer as the soil food web.

Some scientists can spend a lifetime studying one or two species of one soil organism group. Dr. Ingham has identified 25,000 different soil organisms, and when she stopped counting it wasn’t that she had run out of organisms, but that she had more important things to do.

Soil microbiologists say that only about 2 percent of all the different soil organisms have been identified and given names.

What is surplus to these organisms in the soil is made available to the plants along with other minerals held in the soil. The energy cycle is long and involved, and where every living thing is fed and watered and contributes to the growth of other organisms.

Bacteria that cluster around the roots help protect plants from other organisms that would attack their roots. Bacteria are the beginning of the food chain in the soil.

Soil Food Web illustration

Many of them use the finely ground rocks that contain essential elements as the raw materials of soil life. They also need sufficient organic material to feed on and eventually they are eaten by other organisms.

Bacteria have the highest protein content of all soil organisms, so when they are eaten by other organisms, such as nematode worms, some nitrogen is given off — as the nematodes don’t need it all. This nitrogen is then available for plant roots to take up.

When a farmer can manage this process well, the nitrogen is released at a rate that plants can take up, rather than having an excess being available that is wasted and may pollute ground water. The plant can then process the nitrates into proteins.

The protein formed in the plant contains nitrogen and sulfur. This added to the elements, carbon, oxygen and hydrogen make up sugar.

Sunlight provides the energy for the development from sugar and nitrate to quality protein. There are a number of sugar forms as well as many forms of protein.

In my opinion the more complex the sugars and proteins that are formed, the better the quality of the fodder or food.

Plants that contain only simple sugars and nitrates are fodder for plant pests, which are usually simple organisms. Plants need to develop complex sugars and proteins to provide fodder suitable for animals and humans to eat.

However, if the plant takes up too much soluble nitrate at once it cannot turn it all into protein, particularly in dreary weather, and the nitrate in the grass becomes a problem for the animal that eats it.

Nitrates can turn into nitrites which inhibit good digestion and the movement of oxygen in animal blood and muscle.

Much of the nitrogen that plant roots take up is in the form of nitrates. Nitrates contain three parts oxygen and one part nitrogen.

Coriander roots in soil
Nitrates carry oxygen into the plant.

Nitrates carry oxygen into the plant and this oxygen may be more important than the nitrogen. The pore spaces in soil created by active biology enable the soil to hold more air that can sustain plant growth into cooler, wetter weather periods.

Air contains oxygen that is vital to all living things as well as being the most active paramagnetic element on the earth. To get good root growth the soil needs a paramagnetic element.

Where there is oxygen, aerobic organisms are encouraged, while the pathogens that are usually anaerobes are greatly diminished.

If air and moisture are not in the correct ratios in soil pores there is insufficient oxygen and moisture for the beneficial bacteria and fungi, so the pathogenic organisms tend to develop. Pathogenic organisms can breed many times faster than those we consider to be beneficial to the crops we wish to grow.

It is therefore most important that we create the right conditions in the soil to achieve our objectives.

Fungi are another primary organism type in the soil. Some varieties are involved in the breakdown of woody material and dry stalks into soil-releasing nutrients.

Another important type is the mycorrhizal fungi which attach themselves to plant roots where they receive sustenance from the plant and in return draw in nutrients from beyond the reach of the plants roots.

mycorrhizal fungi
Healthy mycorrhizal fungi are key to healthy pastures (image from book)

Mycorrhizal fungi play a key role in collecting up phosphorus and calcium for plant roots.

If soil biology is not working properly, these elements remain locked up in the soil. The fungi are able to hold phosphorus and calcium until the plant needs them.

When you think that each of these species has a specific role in nutrient cycling in the soil, it shows how difficult it would be to replace soil biology with soluble fertilizers and get it right.

Nature knows best! In our time of climate change and weather extremes, it is very important to have a large diversity of soil biology that can provide flexibility.

If you have a range of species, each of which functions at a different temperature or water table level, your pasture can keep growing in a much wider range of weather conditions than pasture that is depending on a few species of biology or on soluble fertilizers.

In order for nutrients to be released by soil organisms at the rate that pasture plants can take them up, it is important to have a well-balanced population of the various types and species of soil organisms. Otherwise you can get a lot of release at the wrong time and the nutrient can be leached. Applying compost teas can sometimes lead to this problem, as the organisms introduced may put the whole soil population out of balance.

Soil organisms help to form humus which stores nutrients and holds water in the soil. Humus increases the flexibility of the soil to sustain plant growth into a hot, dry period and creates a much reduced need for irrigation water. Just 2.2 pounds (1 kg) of humus can hold almost 9 pounds (4 kg) of water.

Steps to Improving Soil Fertility – Observing Your Conditions

The first step is to test your soil, pasture and water to understand what you have in the way of minerals in soil and plant material. At the point of collecting these items you should do a thorough physical examination of the soil, plants and animals, noticing how much air space or crumb structure is in the soil and how many worms are active and at what level they reside.

Earthworms in soil
Worms are a clear sign of soil health.

How often do you take a spade, dig out a scoop from your pasture and have a look at what is going on underneath? Are there worms wriggling about, little hoppers, beetles or millipedes, and white fungal strands? Or does the soil look hard and lifeless? This is one of the initial things I do when I visit a farm, right after observing how the livestock and pasture look.

One thing to notice is whether the organic matter in the root zone is being consumed or is it gathering as a thatch layer? This will vary according to the season and moisture conditions.

Also look between the grass stems for worm castings. How many and how big they are should be noted.

In the pasture, take a look at what species of plants are present, what your animals are eating and in what order of preference they are being eaten.

Then look at the drainage. When it is wet, look at where and for how long the water lies on the surface before soaking in.

Knowing what sort of underlying rock your land sits upon and what sort of history it has had is also important information. How long has it been since the last ash shower, if you farm in an active volcanic region, or was the soil upon which you farm washed in or blown in by the wind?

What was on your land before it was farmed and for how long has it been farmed?

When all this information is assembled you can then decide what actions you should take to improve the performance of your land for what you wish to produce.

This might be to apply minerals that are shown to be in deficit on your soil test. You might also consider applying a liquid fish, seaweed or biodynamic spray.

The main point of difference between biodynamic and conventional farming is that all the nutrients should be biologically available, as opposed to being water-soluble with conventional methods.

This means that a plant can choose to take up clean water when it needs to transpire and can draw up nutrients when and as they are needed. The various measures you can take to activate your soil are discussed in upcoming chapters.

Many farms specialize in one or two enterprises which results in specific fertility needs and pasture requirements. For example, the dairy cow requires a different fodder from beef animals, sheep, goats or horses.

Most of us look to minerals for answers to fertility problems, and many farmers take advice from the sales representatives of the various chemical fertilizer companies. From one aspect this is the cheapest advice but for some it can be the most expensive.

How often does a fertilizer sales agent recommend something that his or her firm does not sell? Consequently little attention is paid to soil biology or the dynamics around life and growth.

Organic farmers generally focus on soil biology, but for the biodynamic practitioner, the dynamics and identity of the farm are the first considerations before soil biology, and biology comes before the minerals.

From my perspective, all of those areas should be integrated together. In farming we are working with life and life processes that are interrelated. Focusing on only one thing can throw the rest out of balance.

When I approach a farmer I inquire about which area they understand best and ask them where they want to go. Then I consider their present farm situation and how the dynamics of energy, biology and minerals can be adjusted to help them work toward their goal.

A farmer’s prime objective should be to get the fodder plants growing like weeds.

My definition of a weed is a plant that self-propagates, grows luxuriantly, and for which one has not yet developed a market.

To get our cultivated plants growing like weeds we often need to make some interventions. These interventions could be the addition of finely ground, mineral-rich rockdust, developing and encouraging the soil’s aerobic biological life or managing the energy or dynamics of our farm environment consciously.

To this end we might be working with composts, a manure heap, or an effluent to which special herbs, seaweed or biodynamic preparations might be added.

This is an extremely simplified look at one or two functions that occur in the soil. I have observed that when we have the whole organism of our farm or garden balanced in every respect, plants and animals are much better able to find the nutrition they need.

Want more? Buy the “Biodynamic Pasture Management” book at the Acres U.S.A. bookstore.

About the Author

Peter Bacchus has years of biodynamic farming experience. Raised on a biodynamic dairy farm, he served apprenticeships on other dairy farms while growing up.

Author Peter Bacchus
Peter Bacchus

He studied and worked on biodynamic farms and in a nutritional research laboratory in Switzerland. Later he worked as a medicinal herb grower, developed a large-scale composting business, and converted a commercial glass house to the biodynamic method, which included successful control of whitefly and fungal problems.

Bacchus consults widely and has held leadership positions in biodynamic farming organizations. He lives with his wife Gill near Palmerston North, on the north island of New Zealand.