Feed the Soil

Feed the soil, not the plant.

Dennis K. Howard

Texas Certified Master Gardener, Certified Vegetable Specialist, Certified Greenhouse Management, Accredited Specialist, American Rainwater Catchment System Association. 

ASSE Certified Rainwater Harvesting Designer and Installer.

Feed the Soil

Feed the Soil, not the plant.

Feed the soil, not the plant. Such a simple concept. We must stop basing our fertilizer decisions on the concept of “feeding plants.”  Fertilizing should not be about “feeding plants” but about feeding the soil.  The plants are only one component of the soil (yes, they are part of the soil biology). 

The basis of all living things is soil — not dirt.  Dirt is the lifeless mineral component of soil.  Soil is a living thing with complex and diverse biology.  It is this myriad life in the soil that makes all other life possible. 

The complex interactions and interdependences of the soil biosphere are far to complex for an article like this.  However, it is such an important part of an organic lifestyle that everyone should have some understanding of what is happening in and around the roots of your plants.

In the Soil

At the bottom of the size scale in the soil biology ladder are the bacteria.  Bacteria are the recyclers of the biologic chain.  There are four functional groups in to which soil bacteria are placed; decomposers, mutualists, pathogens, and lithotrophs. (Ingram, 2009)

Decomposers eat the easy to access carbon compounds and sugars.  They also bind soluble nutrients like nitrogen. 

Mutualistic strains perform several functions.  Some convert atmospheric nitrogen into a form accessible to plants.  Some fix the nitrogen with the need for a host plant by attaching to a plant host and forming nitrogen-rich nodules on the roots of the plant.  These plants are primarily legumes. (Lowenfels & Lewis, 2006)ability (Dick, W., 2009).

Good vs. Bad

There always exist some bacteria with a negative impact.  Pathogenic bacteria are those that cause diseases in plants.  These usually manifest as blights.  If soil is healthy with a diverse and rich soil bacteria population, other bacteria populations produce antibiotics that protect plants from these diseases. (Sylvia et al., 2005).  Feed the soil, not the plants and the soil will keep the bad in balance with the good.

Carbon is not the only nutrient source for bacteria.  The lithotrophs get their energy from sources such as nitrogen or sulfur. 

The More the Merrier

When the soil is healthy and has a rich and diverse bacteria population, a host of different things are happening.  Some of the bacteria produce a layer of polysaccharides that coat the surface of soil particles.  The polysaccharides cause the various particles of clay, sand, and silt to form microaggregates, thus improving soil structure.  Aggregation causes the soil to have a proper balance of open space in the structure.  It is in this open space that allows oxygen movement and water movement (oxygenation and infiltration) into and through the soil.  (Lavelle & Spain, 2005). 

The Give and Take in the Soil

Bacteria also work with plants.  Plants excrete sugars and other compounds into the soil through their roots.  The plant can signal the soil biosphere when it is in stress or if its needs change through this exudation process.  Bacteria respond to these changes in exudates by providing the proper element nutrient or other responses to keep the plant healthy.  Feed the Soil, not the plant and the soil will take care of the plants.

An interesting finding is that tilling soil that has a healthy microbiome creates a more conducive environment for weed growth by raising soil pH and increasing soil nitrates.  Reducing or eliminating tilling allows the soil biological diversity to increase, and the entire biozone to become more balanced. A balanced biozone creates an environment for vegetable and crop plants to be better and more productive.  (Ingham, 2009).

Are you harming or helping?

What we also learn is that feeding plants using the traditional chemical-based fertilizer heavy in nitrogen, phosphorus, and potassium is doing more harm to the soil than it is doing good to the plant.  Man-made fertilizers are all salt based and, as such, tend to build up these salts in the soil.  Salt is a natural antibacterial agent.  High levels of salts in the soil inhibit the growth of bacteria and fungi.  Many larger organisms such as earthworms will avoid soil with high salt levels as well.

Flooding the soil with these three elements interrupts the natural interaction between the plants and the other organisms present in healthy soil.  Without that interaction, the presence of these organisms gradually dwindles.  Without these organisms present, when the plant does encounter stress, the community that would usually respond to the plant’s distress signals is not present and cannot respond. Thus the plant suffers.  The higher level organisms also suffer from the application of artificial nutrients to the soil.  High concentrations of these elements for even short periods can be toxic to earthworms and fungi.

Not a new Concept

The concept of feeding the soil is not new.  Nature has been operating this way for millions of years.  It is only in the last 100 years or so that we have become dependent on the application of toxic chemical fertilizers to our soil to force plant growth.  This growth in the use of chemical fertilizers and the attendant reduction of life in the soil of our agricultural land has been correlated to the decreased nutritive value of the food that is grown, and many other problems climatically and healthwise. Feed the Soil, not the plant!

The move back to an organic approach to gardening and landscape management makes good sense.  It is better for the soil and the plants.  Organic practices mean foods with higher nutritive values, which, in turn, means we are getting better quality nutrition in our diet and become healthier in the long run.

Despite our best efforts, we are beginning to learn that with all our science and knowledge, we cannot improve on the system that has been running this planet for millions of years.  It is time we stepped back into the process and work with it instead of against it.

For much more information on organic gardening, lifestyles and living, visit our website at https://www.westtexasorganicgardening.com.

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•             Ingham, E.R., (2009). Soil Biology Primer, Chapter 4: Soil Fungus. Ankeny IA: Soil & Water Conservation Society. Pg. 22-23. soils.usda.gov/sqi/concepts/soil_biology

•             Lavelle, P., and Spain, A.V. (2005). Soil Ecology, Chapter 3: Soil Organisms, Springer, New Delhi, India

•             Lowenfels, J., and Lewis, W. (2006). Teaming with Microbes: A Gardener’s Guide to the Soil Food Web, Chapter 3: Bacteria, Timber Press, Portland, Oregon.

•             Sylvia, D.M., Hartel, P.G. Fuhrmann, J.J., and Zuberer, D.A. (2005). Principles and Applications of Soil Microbiology (2nd ed.). Edited by David M. Sylva, Pearson Prentice Hall, Upper Saddle River, New Jersey.


Figure 1 Soil Structure, Victorian Resources Online, http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/soilhealth_soil_structure