Soil Fertility is the Key to Successful Farms and Gardens

Fertile soil is the key to successful farms and successful gardens. While every grower I know would agree with this statement, not all would fully understand the entire picture of soil fertility. Today, we’ll take a few moments and discuss the main components of fertile, nutrient rich soils.

Definition of Fertile Soil

The best definition of soil fertility I have found is this one:

Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality.¹

So fertile soils not only sustain plant life but they allow plant life to flourish.

Key Properties of Fertile Soil

To be considered fertile soil, there are a number of elements and soil properties to consider. Here’s the most important:

• Enough Essential Plant Nutrients 

  • There are 17 essential plant nutrients. 14 of these nutrients come from the soil and 3 come from the water and air (Hydrogen, Carbon, Oxygen).
  • The three main nutrients from the soil are the most well known; nitrogen, phosphorus and potassium. Also known as N, P, K. Three additional nutrients fit into this macronutrient group: Calcium, Magnesium, and Sulfur.
  • The remaining nutrients are generally called micronutrients but they are still essential. They include; Iron, Manganese, Zinc, Boron, Copper, Molybdenum, Chlorine, Nickel, Silicon, Sodium.
  • These nutrients must be available in sufficient quantities and in a plant available form.

• Soil pH Generally in the 5.5 to 7.5 Range for Fertile Soil

  • It’s important to note that a change in pH will affect the availability of many of the essential plant nutrients discussed above. Plant nutrients become available or unavailable according to the soil’s pH level.
  • pH will affect the types of crops that will thrive in a soil.
  • Most plants thrive in slightly acidic soil because that pH affords them good access to all nutrients.

• Healthy Soil Structure that Allows for Moisture Drainage and Retention

  • Soil with good structure has a wide range of pore spaces or empty space between the soil particles.  Soils with good structure are generally called granular or crumb type soils. These soils are loose and fluffy. Generally they are high in organic matter and have large soil aggregates.
  • Loamy Soils, a mix of sand, silt and clay, allow for both good moisture drainage and good moisture retention.
  • Good soil structure allows for vital gaps for gases such as oxygen, carbon dioxide and nitrogen. Water logged soils or soils that are too compact do not have the necessary pore spaces to allow for this gas exchange.

• A Thriving Variety of Microorganisms

  • Bacteria, Fungi, algae, actinomycete, protozoa, and viruses all have an important role to play in fertile soil.
  • Soil Microorganisms help recycle nutrients making these nutrients available to the plant. These nutrient cycles are not only important for plants but they also important for all life. Microorganisms participate in the nitrogen cycle, carbon cycle, the phosphorus cycle, and  the Sulphur cycle.
  • Soil microbes are involved in a complex, microscopic food web.
  • Many beneficial soil microbes form synergistic relationship with plants whereby both the plant and the microbe derive a benefit.
  • A healthy, thriving population of soil microbes can help prevent soil pathogens.

• Water Supply

  • Water can make up approximately 2% to 50% of the soil volume.
  • Water is important for transporting nutrients to growing plants and soil organisms and for facilitating both biological and chemical decomposition.
  • Soil water availability is the capacity of a particular soil to hold water that is available for plant use.

Summary of Soil Fertility

The key to good plant growth is fertile, nutrient rich soils. All farms and garden should periodically check their soils for the elements listed above. If deficiencies are discovered most can be corrected fairly easily.

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