Soil Health

Unless you’re using a syringe filled with syrup, you’ve never really fed or watered your plants.


When you irrigate or fertilize your plants, what you are really doing is watering and feeding the soil. It is the soil that feeds and waters your garden and landscape plants. Creating healthy soil is the best way to grow healthy plants that need less protection from pests and diseases, produce more flowers and food, and require less work. So why is improving soil health one of the last things on our garden To-Do lists? Let’s learn more about growing great soil.


What is great soil?
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Soil is a highly complex natural body that scientists call the pedosphere. Some call it the Earth’s living skin. Soil stores water and nutrients, filters our drinking water, helps break down toxic wastes, and is a critical player in carbon cycling, nitrogen cycling, and, let’s face it, life on Earth. Soil is made up of minerals, dead things, living things, gases, and liquids. Great soil has spaces between its bits. These spaces, called macropores and micropores, hold and allow water and gases to flow, carrying nutrients to your plants. Great soil is rich in organic matter. Organic matter is made up of living things, and things that used to be alive. Great soil also contains the 17 primary nutrients required for plant development. But before you can grow great soil, you need to know what you already have.

Healthy soil (Kate Russell)

What is in your soil?

The 17 primary plant nutrients are called macronutrients. Plants use the inorganic form of these mineral elements (read molecule-sized rocks). The only way to really know what is in your soil is with a soil test from a reputable local lab. By local, I mean on whichever side of the Rocky Mountains you reside ~ the tests used are different for each region. The Olson test is better for the West Coast, while the Brays test is better on East Coast.


Now, when your results arrive, you may be little confused by the information. That’s to be expected. Most of us do not read lab results on a regular basis. When I lived in San Jose, California, we tended to have clay soil highly prone to compaction. Aeration was frequently needed. Clay soil tends to contain plenty of most of the necessary minerals, and too much salt and phosphorus. Iron and nitrogen deficiencies are common around here. Other areas and soil types have other strengths and weaknesses. Your soil test results should include percentage ratings for each of the major plant nutrients. It may also tell you how much organic matter is in your soil.


Organic matter in soil

Organic matter is critical to soil health, and it can range from 1 - 8%.  As living things die and begin to breakdown, they add nutrients and improve soil structure. They also alter the electrical charge of soil. Quick chemistry review: molecules can be stable, with no charge, positively charged cations (cat-ions), or negatively charged anions (an-ions). Calcium, potassium, and many other plant nutrients are cations, while organic matter tends to be anions. Plants need both. Ensuring that there is enough organic matter in the soil also improves porosity, aeration, and biological activity.


Soil structure

Soil is usually described as being sand, silt, or clay. Sand is big. You can see individual particles. And water and nutrients can quickly leach away. Silt is made up of medium-sized particles that hold a good balance of gases, liquids, minerals and organic matter. Clay is made up of extremely tiny particles that can hold a lot of water and minerals. [It can also turn into concrete, especially if you add sand.] Organic particles surrounded by clay are protected from the microorganisms that break them down into nutrients that can be used by plants, creating an unattainable banquet. Identify your soil structure with the test found here. Each type of soil benefits from the following:

• Sand - add organic matter to help it retain water and nutrients
• Silt - add organic matter to help maintain the inorganic mineral and organic matter balance
• Clay - add organic matter to improve soil structure and porosity, and to speed the breakdown of organic matter

Do you see a theme here?

Adding organic matter to soil is critical to plant health. A 1% increase in organic matter can make a profound difference in soil structure (aggregation) and chemistry. This helps plant roots get to and absorb nutrients. You can add organic matter to your soil by:

• mulching with untreated chipped wood
• amending with composted kitchen and yard scraps
• incorporating aged manure from local horse and cattle farms
• raising chickens and composting their soiled bedding
• protecting bare soil with ground cover crops
• applying organic top dressings

Nitrogen

Once you’ve increased the amount of organic matter in your soil, you will want to add nitrogen. Nitrogen levels are the single most limiting factor in most gardens, and organic matter can help your plants access the nitrogen that is already present. Nitrogen is a highly mobile nutrient and it is easily lost. Most soils contain less than 1% nitrogen, while 2-5% is ideal. But it is not simply a matter of adding more nitrogen. Which form will you use? Inorganic nitrogen can be found as nitrites or ammonium. When roots take up nitrates, they increase the pH of the immediate area, making it more alkaline. The opposite is true when plants take up ammonium, making the soil more acidic. Organic sources of nitrogen include blood meal and cottonseed meal, both of which will acidify soil.


Soil pH

You can’t know which form of nitrogen is right for your soil until you know its pH. Soil with a low pH makes it harder for plants to access some macronutrients. Soil with a high pH does the same thing. Most plants prefer a pH of 6.0 to 6.5 to thrive. Growing great soil means identifying and managing your soil’s pH. 


Creating healthy soil

Soil creation is called pedogenesis. You can create great soil in your garden and landscape when you:

1. Learn what you already have, with a reliable soil test.
2. Regularly incorporate organic matter with compost, mulch, and even coffee grounds.
3. Analyze your soil structure and aerate, as needed.
4. Only add needed amendments, and in the proper form for your soil.
5. Determine your soil’s pH.

Other ways you can improve your soil’s health is by growing cover crops, using crop rotation, installing foot paths to reduce compaction, and avoiding irrigation run-off and urban drool.

What will you do for your soil today?