Fertile Soil

Fertile soil with seedling

Fertile Soil.  Tell me in one sentence what that two-word statement means to you  I’ll wait.

Ok.  Here is my take on fertile soil in one sentence.

Fertile soil is soil that is sustained by a healthy biome supporting all the biologic processes required to provide essential nutrients to plants and to sustain soil structure.

Let’s step back and take a look at soil. 

What is soil?

Soil has several constituent parts of rock, gravel, sand, silt, and clay, all mixed in various bits and pieces in a range of sizes and different percentages.   The most common types of soil are shown on the chart at the right which is based on the percentage of each type of material found you the soil. 

Soil types chart

Fertile soil is characterized by this mixture of materials being clumped together into what are called aggregates.  More on aggregates later.  In between the aggregates are

  • Air
  • Water (which contains dissolved mineral and organic nutrients)
  • Humus (dead organic material)
  • All the living organic material (worms, grubs, protozoans, algae, fungi, bacteria, plant roots, etc.)
fertile soil with aggregates

It all sounds very simple, but the mechanics, the biology, and the chemistry that goes into building fertile soil is a complex interaction of all of the things listed.

The key question in this article is, from where did the dissolved nutrients that the water is holding come?

The Possible Answers

Those dissolved nutrients could have come from several places.

  • You may have added fertilizer in some form to your soil, and as the chemicals have been dissolved by rainwater or your irrigation system, they have infiltrated down into the soil.
  • Leaves and other organic material have fallen onto your soil, rotted down, and have been digested by the living organisms in the soil making the nutrients in the humus available to the plants.
  • Animal fertilizer has been spread on the garden, and the nutrients present in the manure have infiltrated into the soil.

What’s the difference?

The difference is the support and interactions between plant roots, soil organisms, and the nutrients in the soil.  Fertile soil depends on an active and healthy microbiome, those billions of organisms that live in the soil.

Fertile soil and the soil food web

Plants, as part of their life cycle, produce sugars and other enzymes during the photosynthesis process some of which are exuded back into the soil through the roots.  The bacteria, fungi, and other living organisms in the soil feed on these sugars as part of their life processes and provided the plants with the essential nutrients that the plant requires.  Also, the fungi and bacteria, through a symbiotic process, extend the plants roots systems by many times, acting as a network to return additional nutrients and water to the plant from outside the root zone.  Plants require about 20 different nutrients to be healthy and productive.  That is an important number.  Remember it.

So, these organisms break down the humus (rotted organic material, think compost) and make the nutrients locked into that material available to the plants in a form the plants can use.   

Why not just use fertilizer?

Good question and to understand the answer, let’s look at the common garden and turf fertilizer.  These products are characterized by three large numbers printed on the packaging.  These numbers are usually represented as a hyphenated string like 10-12-4.  The first number represents the amount of available nitrogen in the fertilizer.  The second number shows the available phosphorus and the last number shows the amount of potassium that the fertilizer will deliver.

Remember that number I told you was so important just a moment ago.  20. Look at that fertilizer packaging again.  Do you see anything about magnesium, calcium, iron, or any of the other 20 nutrients that we know plants need to be healthy?  Probably not.

Periodic table with plant nutrients

That is the problem with continual feeding with man-made synthetic fertilizers.  They focus on three nutrients and disregard all the others. 

Don’t the plants get the others from the soil?

For a while that will happen.  The manmade fertilizers stimulate growth in the plant and the soil microbiome.  This increased microbial activity causes the bacteria and fungi to deplete the humus content of the soil.  With nothing on which to feed, the microbiome begins to decline.  Once the humus in the soil is gone, a host of other changes takes place which essentially ruins the soil.

Without the humus, the soil chemistry changes.  Without the microbiome, the soil structure changes.  It is the action of the organisms in the soil biome that create the aggregates that allow the soil particles to clump together, creating spaces for air and water to be present in the soil.  Without these spaces, there is no home for the bacteria and other organisms and there are no places for water to reside to harbor the nutrients the plants need.

Fertile Soil - soil with crusting

The best illustration of this is the crusting over that takes place in many gardens after you water.  You hoe and till the soil around your garden plants, which breaks up the aggregates and destroys the organisms in the microbiome.  The next time you water, without the aggregates, the soil particles nest in tightly together causing that irritating crust on the top of your soil which makes water pool up or run off instead of infiltrating into the root zone.  The tradition answer has been to till or hoe again to try and get the water to infiltrate.  Doesn’t work.

What is the answer?

The answers are simple.

  • Feed the soil, not the plants.
    • Feed the microbiome in your soil.  Synthetic fertilizers do nothing but eventually destroy the microbiome and help deplete the available nutrients, which leads us to the second answer.
  • Quit using synthetic fertilizers.
    • Quit using any synthetic chemically based products on your soil — no pesticides, no herbicides, no synthetic fertilizers, no pre-emergents, etc.  Just stop.  If you have been doing it for years, you may need to investigate our soil remediation system.  Look at that article here.

Sounds simple and it is.  The concept of feeding the soil and not the plant recognizes that it is the life in the soil that makes it fertile and that fertile soil will deliver everything your plants need to grow healthy and productive.  Changing the way we think about soil, plants, and feeding is the key to regenerating soil health and fertility.

More to Learn

We have several articles that go into more detail about each of the concepts shared in this article.  Here are some of the more popular and informative.

Feed the Soil

Fixing Damaged Soil

Soil Compaction

The Organic System – Soil

Composting – A different View

Compost Tea

There are more articles that these listed.  Use the search feature on the website to find them easily.    Our website ist westtexasorganicgardening.com

A few simple changes to your gardening habits can make a tremendous difference in your soil health over some time.  Increased soil health means better soil fertility, better water infiltration and, eventually, healthier and more productive plants be they vegetables, ornamentals, perennials, annuals, and turf.  The principles are the same.