Introduction to Synergistic Agriculture
From the early days of agriculture, the removal of vegetation from the soil as well as plowing were considered necessary, even essential, practices.
However, after years of experience and study, we can say that these practices have been the main causes of soil depletion. They create problems of erosion and loss of fertility through depletion of soil nutrients.
Masanobu Fukuoka, a Japanese microbiologist and farmer, began, from the 1930's, to experiment with a new practice of agriculture.
His experimentation has revolutionary pertinence because it not only eliminates the plow, but it keeps the soil covered with a living permanent mulch during the growth of the plants.
Fukuoka has called this new agriculture Natural, because it is based on synergistic dynamics between the plants and the soil, keeping the soil fertile without the use of chemical or organic fertilizer: since the minerals are conserved, no replacement with compost or manure is required.
Ordinary agricultural rhetoric states that plants absorb fertilizing elements and nutrients from the soil, and these nutrients must be constantly replenished from outside sources. In the natural world, however, plants create their own soil. Is it possible that what they create in nature is destroyed in agriculture?
Maybe the problem is the way we manipulate the soil, and not the plants themselves.
A plant is made of water - roughly 75%. The remaining 25% of dry material is made of organic components, 20% synthesized with the help of sunlight and atmospheric gases, while only 5% of its total weight comes from the soil: in other words, we could say that a plant is made of sunlight and air. Only 50% of this 5% is nitrogen (2,5% of the total weight).
Nitrogen comes from the atmosphere and it can be obtained in a symbiotic way by cultivating plants that fix nitrogen in the soil (thanks to some bacteria that usually live in the soil) , together with edible plants, so that the soil will not become poor.
The other 2,5%, made of minerals, is renewed naturally by the soil: our planet is a sphere made of minerals, covered by a relatively thin layer of soil, composed of living animals (visible or not), fungi, plants and residues. The sun will stop shining before the soil minerals will run out.
Fukuoka demonstrates that agriculture and its processes of planting and harvesting can be practised while respecting the natural cycles of living organisms that have their place in the soil. Natural agriculture is based on the law of synergy and does not follow the first rule of common agriculture that states: if a certain amount of elements is found in a crop, then the same amount of elements must be re-introduced in the soil.
This principle does not take into account the ability of plants to synthesize and convert the elements necessary for their growth. Water and ground plants (with microorganisms and fungi) are at the base of the energetic pyramid; they sustain all other living organisms and they are able to develop the organic substances they need, keeping alive the other living organisms that populate the soil.
Microbial interactions in the soil play a key role in the biological control of plant pathogens, in the turn-over of organic matter and in recycling nutrional elements essential to plant growth.
Plants stimulate microbial activity in the soil, supplying chemical energy by spreading certain elements and substances through their roots (root exudates): the deep connection between plants and soil microbes is evident.
Unfortunately, conventional agricultural methods interfere with this connection. As a result, the soil becomes poor, while the plants are more prone to pathogens.
Oxygen Ethylene cycle
Recent research suggests that up to 25% of the chemical energy of a plant is eliminated in the soil via the roots in the form of exudates containing carbon elements produced in the leaves. This matter is dispersed towards the soil as root exudates or as dead vegetable cells.
But what about this carbon loss, from the plant to the soil?
First of all, these compounds are an energy source for all the micro-organisms that live in the rhizosphere, the soil area near to the roots of the plants.
These micro-organisms proliferate as fast as the oxygen stored in many micro-sites in the rhizosphere is consumed. When oxygen levels decrease, the microsites become anaerobic. These anaerobic microsites have a central role in assuring health and strength to the plant.
At this point, different biochemical reactions begin within these anaerobic microsites, starting with the production of ethylene. Ethylene is a simple gas composite, and it is able to regulate the activity of the micro-organisms in the rhizosphere, influencing the turn-over of organic matter, the cycle of nutrient elements and the influence of harmful elements in the soil.
Ethylene does not kill the micro-organisms, it only inactivates them, producing a resting phase.
This is how the Oxygen Ethylene cycle works:
The microorganisms proliferate inside different micro-sites in the rhizosphere because the plant emits root exudates. These microsites lose almost all the oxygen present, allowing for the production of ethylene: when ethylene rises, the microorganisms reduce proliferation because of the gas.
When this happens, the oxygen consumption is reduced, and thus it remains in the microsites reducing the production of ethylene: the microorganisms resume activity, and the cycle starts again.
Disturbed and wild soils
In wild soils, such as those in a forest, we can register a continuous presence of ethylene; this means that the cycle is active. We cannot, however, measure ethylene in significant amounts in soils disturbed by conventional agriculture techniques.
When natural ecosystems are disturbed for agricultural use, there is a substantial decrease in the amount of organic matter in the soil, the plants lack nutrients and pathogen concentrations increase drastically.
Plowing is one of the main activities that inhibits ethylene production in the soil, changing its nitrogen composition.
In wild soils, nitrogen is present as ammonium, with traces of nitrates. When the soil is disturbed, the composition of the soil changes, and nitrates become much more common. In fact, plowing stimulates the activity of a specific group of bacteria that converts ammonium to nitrate: plants and microorganisms can use both of them, but ethylene cannot be produced when there is too much nitrate, because it inhibits the creation of the anaerobic microsites.
The Iron role in ethylene production
When all the oxygen is consumed in the microsites, a series of chemical reactions begins. One of these reactions is iron transformation, from the oxidized or ferric form to the reduced or ferrous one.
Iron is one of the main elements in soil composition, as it represents from 2 to 12% of its weight. In wild soils, all the iron exists as tiny crystals of iron oxide, immobile in the soil.
Without oxygen, these crystals convert to their ferrous form, highly unstable. But how does ferrous iron stimulate the production of ethylene?
Ferrous iron reacts with an ethylene precursor that is already in the soil, and produces ethylene as a result. This precursor is produced by the plants, but it is present only in old and dead leaves. When these leaves fall on the ground and start to decompose, the ethylene precursor goes into the soil, and remains there until the oxygen level in the microsites decreases; the iron oxide becomes ferrous iron and reacts with the precursor, producing ethylene.
It should not be surprising that ethylene precursor is stored in old or dead leaves. After all, in a forest old and dead leaves are the main components of the soil. It is common knowledge that in conventional agriculture almost every leaf and every residual dead plant has to be removed in several different ways, for example by burning the fields. In this way, ethylene cannot be produced at all because of the absence of its precursor.
Another problem in disturbed soil is the inadequate amount of nutritional elements; this is the main reason why conventional agriculture uses chemical or organic fertilizers. This shortage in nutritional elements occurs even if they are present in the soil usually in a highly insoluble form.
The anaerobic microsites in the rhizosphere that, as we have seen, are essential for ethylene production, can play a very importart role in the mobilization of these nutritional elements by converting them to a soluble form.
This proces is strictly linked to the role of iron in soil. In wild soils, the iron is present as tiny crystals of oxide with a wide surface. These crystals are electrically charged. Nutritional elements such as phosphates, sulphates and other micro-elements are bound to this surface. In this form, they are not available for the plants.
However, when anaerobic microsites develop following the decrease of oxygen in the soil, the oxide turns into ferrous iron, releasing the micro-elements on its surface so that they can be used by the plant. But this is not the only process in which iron is involved.
Other fundamental plant nutrients, such as calcium, potassium, magnesium and ammonium, bind to clay particles or other organic matter. Ferrous iron acts to free them by binding to the organic matter in place of the nutrients that are now free to feed the plants.
It is interesting to note that nutritional elements become available to the plants inside the anaerobic microsites, near the rhizosphere, exactly where they are needed.
Another aspect of this mechanism is that it naturally prevents soil depletion: even if the mobilized nutrients are not used by the plants, they cannot be flushed away because the iron reoxidizes once it has migrated to the margins of the microsites, creating new oxide crystals. In this way, basic nutrients again bind to the crystals and again become available during the next cycle.
Please note that the necessary conditions for this process are exactly the same needed for ethylene production.
In disturbed soils, where ethylene production is inhibited by plowing, even this mechanism is blocked, and the nutrients will not be mobilized.
Correct soil management requires a huge move away from conventional agricultural practices, such as tillage, which is done to aerate the soil. In fact, tillage produces a sudden increase of plant growth in the short term, but considering its consequences in the long term we will find that plowing generates problems of soil depletion.
New agricultural methods that move away from plowing assure a continuous plant growth while keeping the soil fertile.It is essential to cover the soil with mulch, increasing the amount of organic matter that returns to it. Is is good to use mature plants as mulch, leaving them on the ground, without burying them.
It may be difficult for the modern agronomist to understand these subtle ecological processes because of their holistic complexity, but this limit to lateral thinking should not prevent us as humans in a global society to find sustainable ways to produce food without destroying the soil.
Synergistic agriculture aims to create the conditions needed to keep the soil alive and in good health, maintaining its fertility. The process necessitates reproducing the dynamics of soil self-fertilization that usually occur in nature: this is the main difference between synergistic agriculture and conventional/traditional agriculture, and it translates into a completely new system of knowledge.
Changing habits is not easy, and if habits are supported by tradition, chemical industries, agronomy faculties and current practice, the task will be huge.
We require a deep belief in the need for change, preparing ourselves for a future in which oil, fertilizers and soil will be scarce.
In some parts of the world it is already hard to find manure or compost for soil, so the knowledge of production techniques that rely on soil self-fertilization can be vital. We should start to put into practice this knowledge as quickly as we can, even in small experimental fields, so that one day we will be able to advise farmers on how to change their practices towards sustainable methods, and we should do so in all climate conditions.
This research is in its initial phase in many places around the world. We are members of this movement for change, a growing group which will make up the critical mass necessary to go one step beyond the actual situation. The challenge now is to feed a population in exponential growth, while at the same time dealing with the reality of depletion of soil fertility.
Fertile soils are always covered by many different plants, so we could argue that soil needs to be always covered, with its surface full of small plants even while it is used for agriculture.
If we prevent the problems caused by soil depletion (erosion, flushing and loss of organic matter mainly caused by tillage), the residual organic components left in the soil will be much more than the 5% of nitrogen and other nutrients used by the plants in their growth.
Without disturbing the soil and the processes within it, there will not be any need to use fertilizers, so the work needed to produce compost will be reduced, and thus for any other kind of fertilizer. There will be no need for treatment with fungicides or pesticides.
In synergistic agriculture, fields, gardens and plantations have to be re-arranged so that the symbiosis between plants, bacteria, fungi and every living or mineral element will create a dynamic synergy: this self-fertilizing process will allow for the growth of edible plants for us without depleting the soil.
- L'arte di coltivare lasciando fare alla terra, Corso Teorico-pratico, Libera Scuola di Agricoltura Sinergica Emilia Hazelip, tradotto da Fortunato Fabbricini e Anna Fanton dai testi di Emilia Hazelip
- The living soil, Oxygen-Ethylene Cycle, Permaculture College Australia
- L'Azoto e le piante
- Elementi nutritivi, Ferro
- wikipedia:No-till farming