High Cation-Exchange Capacity vs. Low Cation-Exchange Capacity: What You Need To Know 

What is Cation-Exchange Capacity (CEC)?

Cation Exchange Capacity, or the CEC number, measures the soil’s ability to hold positively charged ions. Cations are positive ions, and anions are negatively charged ions. There are plenty of positively charged ions in the periodic table, but to get the most out of your soil, there are certain elements that you want to ensure are in the correct ratio. Their primary uses are to offer the proper requirements for any root system’s proper growth and development.

What Are The Most Important Cations For Soil Growth?

• Nitrogen (N)
  • It is important for plant growth (structure), plant food processing, and the creation of chlorophyll. Without the proper amounts of nitrogen, plant growth will be limited. Due to the limited size of plant growth, you will not be able to see your plants grow to their full potential.
• Phosphorus (P)
  • This nutrient is extremely important for root growth and winter hardiness. Without proper rooting, your plant can be subject to blowing over in strong winds. Winter hardiness is important for plants that thrive in cool weather or need sustained nutrients to get through the cold and into the next growing season. On top of all of this, phosphorus will quickly help your plants reach maturity.
• Potassium (K)
  • Potassium helps your plants grow their roots and be resistant to droughts. Think of it like this: no quality roots, no drought resistance. Essentially, you need potassium to help your plants grow no matter what weather may come.
• Calcium (Ca)
  • Calcium helps to build strong plants at the cellular level. The proper amounts of calcium in the soil will help strengthen the cell walls of your plant. Just like in people, calcium helps build strong bones; calcium helps build strong plants.
• Magnesium (Mg)
  • Having the right amount of Magnesium is central to chlorophyll molecules. Without chlorophyll, photosynthesis cannot take place properly. Ultimately, this will result in lower-quality plant growth and formation.
• Boron (B)
  • To have the cell wall form properly, you need the right amount of boron. Having this proper amount of boron in the soil will provide the proper maintenance of structural and functional integrity in biological membranes. This allows for proper movement of sugar (energy) into the growing part of the plant, thus allowing proper pollination and proper seed set production.
• Copper (Cu)
  • Copper is required for many enzymatic activities in plants, including chlorophyll formation and seed production. These enzymes are used as biological catalysts. Catalysis is used to reduce activation energy, thus allowing reactions for activities in plant growth to occur easily.
• Iron (Fe)
  • Iron is integral to the synthesis of chlorophyll and is essential in the maintenance of chloroplast structure and function. Without chloroplasts, the photosynthetic process of turning light energy into chemical energy cannot occur properly, leaving you with sad plants.
• Manganese (Mn)
  • Manganese sustains the metabolic roles within different plant cell compartments. These metabolic roles include pathways for protecting themselves against droughts, pests, and herbivores. Without the proper level of manganese, the beauty of the flowers, as well as pollination production, is severely diminished.

Why Does CEC Matter?

Now that you understand that CEC is the soil’s ability to hold and exchange positively charged ions (cations), it’s important to note that not all soils have the same CEC. 

CEC values vary depending on soil composition, so whether your soil is made up of clay, silt, or sand will cause your CEC number to differ. Soils with a high CEC number tend to retain more nutrients and moisture, while low-CEC soils drain faster but require more frequent fertilization. These differences directly affect your plant’s health, fertilization strategies, and soil management practices.

To better understand high vs. low numbers and how they affect soil performance, let’s look at how each type influences nutrient availability and plant growth.

High Cation-Exchange Capacity

Soils with a high cation-exchange capacity have a greater ability to hold and exchange positively charged nutrients (cations). This allows these soils to store more essential plant nutrients and prevent the risk of nutrient loss through leaching. Many farmers, gardeners, and landscapers seek soils with high CECs because they support plant growth and require less frequent fertilization.

What Type of Soil has the Highest Cation-Exchange Capacity?

Clay soils and soils rich in organic matter have the highest cation-exchange capacity (CEC). This means they can hold onto more nutrients and make them available to plants, which supports healthy growth. Clay particles are very small and carry a negative charge, which helps them attract and hold positively charged nutrients like calcium, magnesium, and potassium. 

Beneficial microbes contribute to improved structure by supporting aggregation, especially when combined with organic matter and good soil management practices. This improves soil aggregation, making it more porous and better suited for root growth and water movement.

What Does It Mean If I Have High CEC Numbers?

Higher CEC numbers mean that your soil will hold onto the key nutrients mentioned above, such as calcium, magnesium, potassium, and ammonium. It also requires less fertilizer, maintains pH stability, and retains more water.

What To Do For Soils With High CEC?

Soils with high cation-exchange capacity (CEC) can hold more nutrients, and due to their finer texture or higher organic content, they also often retain more water, which generally benefits plant growth. In many cases, high-CEC soils are beneficial and require fewer nutrient amendments, though they may still need structural or drainage improvements depending on their composition. Clay-rich, high-CEC soils may face structural challenges such as compaction, poor drainage, and restricted root penetration, which can limit plant health if unmanaged.

For Compacted High CEC Soil (Clay Based)

While high-CEC soils typically support fertility, clay-based soils in this category can become compacted or poorly aggregated, leading to poor drainage, reduced airflow, and root growth issues. Adding beneficial microbes alongside good soil management practices can gradually help improve soil structure. Here are some signs that your high-CEC soil may be struggling:

Buffering Effect: In some instances, due to their strong nutrient-holding capacity, changes in soil chemistry (like pH or base cation levels) may take longer to show results from fertilizers or amendments. Here is a study from Purdue verifying this claim.

Slow Drainage: Clay-rich, high-CEC soils tend to hold water longer and may become waterlogged.

Compaction: These soils can become dense, restricting root growth and limiting oxygen availability.

How Soil Microbes Can Help

Improving the biological life in your soil is one of the most effective long-term strategies to enhance structure and function—especially in high-CEC soils that suffer from compaction or poor aggregation.

• Microbial Activity Builds Soil Structure: Soil microbes break down organic matter and produce natural sticky compounds that help bind soil particles into small, stable clumps called aggregates. https://extension.psu.edu/soil-microbiome-functions-of-a-community
• Better Drainage and Airflow: These aggregates increase pore spaces in the soil, enhancing water movement and oxygen availability for plant roots.
• Reduced Compaction: As aggregation improves, the soil becomes looser and more crumbly, making it easier for roots to grow and access nutrients.
• Long-Term Soil Health: A thriving microbial community supports nutrient cycling, moderates water movement, and contributes to a more balanced and resilient soil ecosystem.

Note: For significantly compacted soils, microbial inoculants work best when combined with physical or organic amendments like compost, aeration, or cover crops.

Low Cation-Exchange Capacity

Before Soil Care

After Soil Care

Soils with low cation-exchange capacity (CEC) have a limited ability to retain and exchange positively charged nutrients (cations) such as potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and ammonium (NH₄⁺). As a result, these essential nutrients leach away more easily, which means plants in low-CEC soils often require more frequent fertilization to stay healthy

What Type of Soil Has the Lowest Cation-Exchange Capacity?

Sandy soils typically have the lowest CEC, often in the range of 3 to 5, occasionally reaching up to 10. These soils lack the fine particles and organic matter needed to hold on to nutrients effectively.

• Silty soils have a moderate CEC, ranging from 10 to 20, while
• Clay soils and organic soils can have very high CEC levels, often exceeding 30.

If this concerns you, raising the CEC number of sandy soils with microbes is possible.

Is Low CEC Bad?

Not necessarily. Like many soil traits, low CEC has both advantages and disadvantages:

Advantages:

• Excellent drainage and aeration.
• Rapid response to fertilizers and soil amendments.
• Easier to adjust pH since low-CEC soils buffer changes less.

Disadvantages:

• More susceptible to pH swings, which can affect nutrient availability.
• Nutrients are easily leached away, especially in high-rainfall or irrigated areas.
• Requires more frequent fertilization.

What Should You Do If Your Soil Has Low CEC Numbers?

Low-CEC soils can support healthy lawns and gardens with proper management and constant fertilization. However, their ability to hold nutrients is limited, which can cause plants to show signs of deficiency more quickly.

If your CEC values fall in the very low range, you may notice:

• Yellowing or stunted growth in plants
• Thin, patchy turf
• Low organic matter levels in the soil
  

Amending your soil to improve its nutrient-holding capacity is a good idea in these cases.

How Can I Fix A Low CEC Number?

1. Increase Organic Matter

The most effective and natural way to improve CEC is by increasing the soil’s organic content, which has high CEC.

You can do this by:

• Incorporating compost, manure, or humus
• Incorporating mature compost, well-decomposed humus, or carefully selected biochar can help improve CEC.
• Rotating in cover crops and minimizing tillage to build long-term soil health

2. Use Soil Microbes Strategically. Although microbes don’t directly raise CEC, they help build organic matter, increasing the soil’s capacity to retain nutrients.:

• Decomposing organic matter, which adds CEC-building humus
• Cycling nutrients, making them more plant-available
• Improving soil structure, which helps retain moisture and slow nutrient leaching

The Rhizophagy Cycle:

The Rhizophagy Cycle, a recently discovered microbial-plant interaction described by Dr. James White, illustrates how certain microbes can enter plant roots and contribute to nutrient transfer. Though not yet fully understood or common to all plants, it offers insights into plant-microbe relationships.

What Benefits Do Microbes Provide to Their Environments?

• Contribute to a balanced and resilient soil ecosystem
• Soil microbes contribute to plant and soil health in many ways:
• Break down organic matter into carbon-rich humus
• Release phosphorus bound in soil aggregates
• Supports nitrogen fixation (via specific bacteria)
• Help plants tolerate saline or contaminated soils
• Enhance soil structure and porosity
• Promote root development and nutrient uptake
• Suppress soil-borne pathogens
• Improve fertilizer efficiency

What is a Good CEC in Soil?

Cation-exchange capacity (CEC) measures the soil’s ability to hold and exchange positively charged nutrients like calcium, potassium, and magnesium. For turfgrass and lawns, there’s no single ideal CEC value—instead, the best CEC depends on your soil type and how you manage it.

• Sandy soils typically have a low CEC (often 3–10), meaning they hold fewer nutrients but offer excellent drainage.
• Loamy soils may fall in the moderate range (10–20), balancing nutrient retention and aeration well.
• Clay or organic-rich soils have a high CEC (20–40+), allowing them to retain more nutrients and water.

While turfgrass can thrive across this spectrum with proper care, high-CEC soils—when managed well—often support the most lush, dense, and vibrant turf, thanks to their superior nutrient and moisture-holding capacity.

How To Test & Adjust CEC in Your Soil

If you want to ensure your CEC numbers are in a good range, you’ll need to measure and test your soil, calculate its CEC, and then take the steps to adjust them. 

How To Calculate Cation-Exchange Capacity

Some, but not all, Soil test kits report CEC numbers, so it’s important to make sure that they will be reported before purchasing soil testing kits.

We recommend using SoilKit.com. They have easy-to-read results and step-by-step instructions. There, you can purchase just one or a two-pack to see how microbes and other additions have changed things.

And a pro-pack for contractors and landscapers who want to give their customers data like no one else can.

Choosing the Right Plants for Different CEC Levels

Below are some plants that do well in high or low CEC soils:

Best Plants for High CEC Soils

• Tomatoes
• Beans
• Cabbage
• Leafy Greens

Best Plants for Low CEC Soils

• Lavender
• Cacti & Succulents
• Corn
• Carrots

Want Higher CEC Numbers?

As mentioned above, the ideal range of the cation-exchange capacity (CEC) number is between 15 and 25. This means that all your macro and micronutrients are being utilized and delivered in the soil efficiently, making your lawn, gardens, and landscape more beautiful and low-maintenance than ever.

With soil health improved and dialed into the proper CEC number range, you will save time and money on fertilizers, pesticides, and water!

If you want to increase your CEC numbers,  visit our soil microbes page, contact us directly, call over the phone, or visit us in person at Sauders Hardscape Supply. We’re here to help you improve your CEC numbers and provide your soil and plants with the proper nutrients to create a beautiful landscape.