For all my years in the classroom, I never let students say the “d-word” when discussing soil science. In some instances, we had a “d-word” swear collection jar of a quarter when you used the term and even today, I hesitate from spelling the word out in text due to feedback from all those I have corrected. In case you still need a clue on the “d-word”, it ends in irt.
As a horticulturist for 46 years, I have read, heard, and been told many secrets to growing good plants. I still hold firm that without proper knowledge of how soil works, most of what we do is by chance. Soil is a living entity comprised of parent material (sand, silt, and clay), air, water, organic matter (OM), and microorganisms. It is this last item which makes our soils come to life. If you have pets, then you know they need shelter, warmth, air, water, and food. From this point forward think of soil microorganisms as the pets in your soil. If you take care of them, they will take care of your plants.
There is a huge difference in habitat from a sandy soil to a healthy soil with a good percentage of OM (5% – 10%). In one gram of healthy soil (the weight of one standard paper clip), you can have bacteria (100,000,000 to 1,000,000,000), actinomycetes (10,000,000 to 100,000,000), fungi (100,000 to 1,000,000), protozoa (10,000 to 100,000), algae (10,000 to 100,000), and nematodes (10 to 100) (1). A teaspoon of healthy soil can contain over four billion organisms (2). These microorganisms are part of the soil food web and they form a relationship between soil and your plants. They help convert nutrients to useable forms and assist with other plant functions.
The question becomes how to take care of your soil pets. For years we have performed practices that compromise these populations. Growing up we put all of our grass clippings in the weekly trash. We know now how valuable those clippings are and to leave them be. Two practices still common today though are tilling and raking leaves.
Tilling has a limited purpose. If I place a layer of organic matter on top of the ground, then tilling incorporates the OM which feeds my pets. Excess tilling of soil introduces large amounts of oxygen which accelerates the breakdown of OM thus reducing our pet populations over time. Another adverse result from tilling is disturbing the soil structure (how the parent materials are arranged) which can reduce pore spaces thus limiting water percolation and root growth. There is a reason agriculture has adapted no-till practices.
Raking leaves (supposedly the sign of a well-kept yard) is removing large amounts of OM. Do you ever wonder why trees in a forest thrive? All of their leaves fall to the ground and are recycled by the microorganisms. Each of those leaves contains macronutrients (carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, sulfur, and magnesium) and micronutrients (boron, copper, chlorine, iron, manganese, molybdenum, nickel, and zinc) which are necessary for plant growth. You would be hard pressed to find all those nutrients in one fertilizer bag. So recycle (compost) your leaves versus having them removed from the property.
We are in our off season and tasks such as improving soil health should be considered now for soils to be ready in spring. Remember a little organic matter at a time and never work wet soils. As your OM levels build over the years, remember to change your watering and fertilizing schedules as the soil will be better adapted at holding water and nutrients. Soil tests are still recommended before fertilizing.
If you would like more tips on improving your soil, contact me or your local county horticulture extension agents. For a more in depth look at caring for your soils, read The Importance of Soil Health in Residential Landscapes by Sally Scalera MS, Dr. A.J. Reisinger and Dr. Mark Lusk (https://edis.ifas.ufl.edu/ss664).
- Chapter 2: Soils, Water, and Plant Nutrients. Texas Master Gardener Training Manual.
- The Importance of Soil Health in Residential Landscapes. 2019.