Understanding the Soil Fertility Cycle

February 1, 2018

To reduce our dependence on applying commercial fertilizers and chemicals, we must first understand how the soil fertility cycle truly works.

The breakdown of organic matter follows a complex pattern teeming with legions of microbes, each fulfilling its own specific role.

The Breakdown of Organic Matter

In the first stage of this cycle, called putrefaction, toxins are produced, which are harmful to soil organisms and may retard plant growth. With the presence of oxygen, moisture, and proper temperature, this portion of the breakdown will be completed in about two weeks. If there is a lack of oxygen due to poor soil structure, this period may be lengthened, which will result in the contamination of the soil by toxins such as formaldehyde, hydrogen sulfide, and methane. This contamination can also occur if organic matter is incorporated too deeply into the soil.

Once putrefaction is completed, the decomposition stage begins. Here, many organisms thrive in the struggle for life. Organisms are consuming organic matter that is digested and transformed into plant-available food. It is after this stage that the organic residues are collected in water—along with amino acids and the salts of humic acid—to form soil plasma

Soil plasma is a jelly-like substance that coats soil particles and clay crystals to form the clay humus complex, or stable humus. The formation of stable humus is probably the single most important event in creating good soil fertility. Each of nature’s organisms must play its part in the cycle to achieve this transformation. Once stable humus is formed, it becomes an efficient warehouse for plant nutrients. The sticky humus along with polysaccharides, which are complex sugars from the excrement of microorganisms, bind particles together in clusters or aggregates. These are the aggregates that give fertile soil its crumb-like structure or tilth, as well as porosity. Aggregate structures, due to the irregular shape of the soil particles, provide a large surface area for the soil solution to adsorb (cling) to.

The soil solution, or liquid portion of the soil, is made up of water and nutrients. This solution provides microorganisms with the ideal habitat. Good soil structure promotes an increase in their population and also provides many other benefits. Due to its aggregate (crumb-like) structure, it provides increased porosity. This porosity increases moisture retention and allows necessary oxygen to penetrate to greater depths. It also provides protection against erosion by both wind and water.

Uptake of Nutrients

There are various ways in which plants receive nutrition. Minerals are held in the soil in the form of crystal lattice ions. These ions become available in nature at a continuous (but very slow) rate, either by weathering or biological release. Weathered ions become free ions and are stored in the soil solution. By being part of the liquid portion of the soil, they are prone to loss by leaching. On the other hand, biologically released ions become swarm ions and are attracted to stable humus. They are stored there and become readily available to the plant on command.

Chemical fertilizer advocates believe that for the fertilizer to be efficient, it must be in a soluble form. Unfortunately, it takes an excessive use of salts to achieve this solubility. In the soil solution, these mineral nutrients are in the form of free ions, and the plant then must take up water from the soil to receive the nutrients. The nutrient balance for the plant is controlled by the type and amount of nutrients supplied by the applied fertilizer. Plants in search of nutrients will absorb extra quantities of water in search of minerals that are not available.

cation exchange
‍To access nutrients, the plant roots release a hydrogen ion to the clay humus colloid, which in turn, releases a mineral ion to the plant in a process called the cation exchange.

To access nutrients, the plant roots release a hydrogen ion to the clay humus colloid, which, in turn, releases a mineral ion to the plant in a process called the cation exchange.

On the other hand, nutrients in the form of swarm ions are readily available to the plant on an exchange basis. Only the minerals desired by the plant are exchanged; the balance is held in the humus for future use. In this exchange system, the plant uses water only for cooling and to carry out its biological functions. To access nutrients, the plant roots release a hydrogen ion to the clay humus colloid, which, in turn, releases a mineral ion to the plant. The colloid then releases the hydrogen ion, which is an acid, to the mineral crystal lattice, where, through biological interaction, the hydrogen or acid is used to release an ion of mineral to the colloid. This is commonly called the cation exchange. Some nutrients in the form of free ions are taken up by the plant in the soil solution, but these are not the key nutrients required for the process of photosynthesis.

With these biological actions taking place in the soil on a steady basis, adding unwanted minerals can cause an imbalance between swarm ions and free ions. When the plant demands its selection of nutrients, it receives elements in a balanced formula. When combined with amino acids and enzymes, this triggers the mechanical and biological functions within the plant cells. This is the only way the plant can synthesize the full balance of nutrition in its cells.

Extraordinarily, plants receive approximately 85% to 95% of their required nutrients from the atmosphere. 

This amazing accomplishment happens through biological interactions such as photosynthesis. Excessive use of salt-based soluble fertilizers severely inhibits these natural processes, and microbial activity is severely diminished. Without interference from salt-based fertilizers, nature has built-in checks to maintain the balance of nutrients in the soil.

Destroying Soil Structure

Soil degradation began with our ancestors, who unknowingly started the process as soon as they broke virgin sod with the plow. We have learned that soil microbes are both aerobic and anaerobic. The action of the plow was to turn the soil over. However, this placed the aerobic (air-breathing) microbes down deep where there is no air, and the anaerobic microbes (those that cannot live in the presence of air) up on top. This action not only caused billions of microbes to perish, but also decimated the levels of organic materials, making them too low to adequately perform their important role in the fertility cycle.

As if this was not enough, our ancestors cut their crops and carried them to a central spot to be threshed, thereby removing the microbes’ food source. Then, after having what straw they needed for their farm animals, they cleaned up the fields by burning the straw stacks and the stubble. Soon they found they could not continuously crop the soil and started the practice of summer fallow. Now they could produce a fairly decent crop every other year. 

During the fallow year, the farmer used extensive cultivation to keep the land black, requiring soil microbes to live off of a minimum food supply only every other year. Added to this was the over-cultivation that threatened soil tilth and destroyed the natural habitat of the microbes. As the soil was degraded, the life-building humus was also depleted, causing decreased yields and the breakdown of quality in our produce. 

Farmers knew they had to do something. Unfortunately, what began were poor farming practices such as chemical fertilization, backed up by principles such as the “balance sheet theory.” The results were amazing and the farmer entered into an era of prosperity that may never be equaled. Fertilizer was inexpensive and reasonably easy to use. The practice lead to increased yields and the belief that more is better.

Unfortunately, some fertilizers have very damaging effects on the soil and its microbial population. 

It is not my intention to single out one product, but in the search for information we must do so. Anhydrous ammonia—being one our major sources of nitrogen fertilizer—is particularly harmful. Anhydrous ammonia was used extensively in World War II as a method of making soil hard for airplane runways. This was accomplished by the breakdown of the soil structure. Any ammonia type fertilizer added to soil has the devastating effect of dissolving the stable humus and placing it in the liquid portion of the soil. This places excess amounts of nutrients in the soil solution, thereby giving the anhydrous ammonia a false valuation as a fertilizer. Add to this the tremendous numbers of free hydrogen ions, and now you have a hydration process similar to that in concrete. Fields with long anhydrous use become very hard and compacted over time with very poor moisture retention. This brings on a hydroponic solution where the soil is merely a medium to hold the artificial nutrient plus the seed. 

Other chemical fertilizers limit nature’s cycle just as much. As we progressed into chemical agriculture, we noticed that pest problems were becoming more prevalent. The solution seemed easy. All a farmer had to do was spray pesticides and his fields were made clean again. 

We have now reached the point where the breakdown of the soil structure and the loss of porosity causes anaerobic soil conditions. Anaerobic soil conditions occur when the life-giving oxygen cannot penetrate the soil. Such conditions are evidenced by increasing salinity areas, hard pan conditions, and soil that seems to have lost all its fertility. Crops refuse to grow even with the addition of commercial fertilizers. When the aerobic microbes cannot survive, the breakdown of organic matter must all be achieved without the aid of oxygen. Furthermore, the final breakdown and transfer of nutrients to plants cannot be achieved.

These practices have led the modern farmer into a no-win situation where his input costs are surpassing his potential earnings from his crop. 

Farmers must stop thinking that chemicals, like a magic wand, will cure all their problems. Unfortunately, modern research is doing little to help. These research facilities, fueled by major corporations with vested interest, seem to be working the problem backwards. They are busy trying to develop new and more efficient chemicals and chemical resistant strains of crops to deal with the degraded conditions. We should be trying to correct the causes of our problems rather than trying to mask the consequences.

While this practice continues, the rest of society will view farmers as polluters. These wonderful new pollutants that are developed by research become the ultimate responsibility of the farmer. The absurdity of the whole situation is that North American farmers pay billions of dollars each year to promote further soil degradation. 

It has been well documented that pests attack the weak. As the wolf in the wild selects the sick and crippled deer, likewise, insects select the unhealthy plant. This theory also holds true for weeds. As our soil degrades, nature provides us with a warning that something is wrong. This happens when the natural fertility declines leaving an imbalance in the soil. Mother Nature then brings forth weeds to try and restore the balance. This is accomplished through the ability of certain weeds to flourish in deficient conditions. Weeds are incredible transportation systems for soil nutrients. Long tap roots reach down into the subsoil seeking needed minerals. When the weed dies and is incorporated into the soil it carries the nutrients back into the ecosystem. The solution is simple if we recognize the cause of the problem instead of only dealing with the result.

Farmers who have adopted natural systems of soil management have found that weeds and insect problems decrease to a negligible level as the soil regains its balance. 

Rebuilding Soil Structure

Now that the farmer is caught in an ever tightening spiral of soil degradation and increased input costs, how can he step back into a more sustainable system of agriculture? The first step is to reshape his thinking and attune himself with nature. A farmer can never outsmart nature because he is part of nature himself. 

Thousands of farmers, farming millions of acres around the world have found such a system—sustainable farming. Some call it biological farming, others biodynamic farming, but whatever the label, it is working for those who wish to try. We have looked at the causes of our problems, now let’s look at some solutions. Some farmers may use various techniques, but most programs are very similar. 

The first requirement is an analysis of the problems on each individual field. The major concern in rebuilding the soil is the percentage of organic matter contained in the soil. If the organic levels are from 1 percent to 3 percent, measures must be taken to replenish the level. Incorporation of manure or other organic wastes are one way to achieve this. If this material is not available, it may be necessary to grow a green manure crop. If you are summer fallowing, this can be accomplished in the fallow year. If you are continuous cropping, it can be achieved by planting and harvesting an early crop for feed and then planting a fast growing crop such as German oil radish. Good cover crops include: sweet clover, lupines, sorghum-sudangrass or rye. The establishment of increased organic matter is of the greatest importance as it is an absolute requirement for building stable humus.

Reduce your normal fertilizer application and herbicide usage by at least half. When the soil has become addicted to chemicals, it is not possible (in all cases) to eliminate these chemicals the first year. As each crop year goes by, you should be able to reduce or eliminate the use of fertilizer and chemical sprays. Plant your crop with microbial soil inoculants to ensure that the microbial population can reach levels that are required to carry out the necessary functions in the fertility cycle. You must also add a readily available source of nutrients for the plants. Even if you have incorporated fresh organic material, it may take weeks or months before the microbial population turns it into plant food. Fortunately, there are some high quality plant foods available on the market today that have very low salt contents.

Speak with a biological consultant about your particular soil conditions and he can help set up a program that will fit your individual needs as well as guide you through the first stages until you gain a basic understanding of how to deal with your soil. 

The biological, or sustainable, farming system has been developed by farmers and private research.

The conversion to biological farming is not as difficult as you think. In fact, the closer you work with nature’s laws, the easier it becomes. 

I hope that, by reading these pages, you have gained a new perception of some of the problems facing modern agriculture. If you agree that farmers must move forward into a new era of working within nature’s laws, please share this message with others. With a renewed perspective, farmers can once again carry themselves with pride, mindful of the fact that they are Guardians of the Soil.

Read the prelude to this article, Understanding the Soil.

George Sims