By JASON GRAVES
K-State Research and Extension
Central District Horticulturist
Soil is the foundation of plant growth, making it one of the most discussed topics whenever I interact with local gardeners. Good soil health is crucial in growing our plants to their full potential while minimizing problems like stress, pests, and diseases. However, many gardeners face challenges due to less-than-ideal soil conditions. Our local soils may have high clay content, high pH levels, low organic matter, compaction, or other issues that hinder plant success.
The key question is: How can soil be improved? Fortunately, there is a fairly simple answer that will help anyone with any soil type: add organic matter.
Add organic matter
Incorporating organic matter is one of the most effective ways to improve any soil. This practice benefits all soil types. In sandy soils, organic matter acts like a sponge, helping to retain moisture and nutrients. In heavy clay soils, it enhances aeration and drainage by promoting the formation of soil aggregates. Additionally, organic matter serves as both food and habitat for soil microbes, which play a crucial role in breaking down nutrients and making them available for plant growth.
Various organic matter sources can be used to enhance soil health. Common options include compost, aged leaves, well-rotted hay or silage, peat moss, composted manure, green cover crops, and untreated grass clippings.
How organic matter works
Soil has several key components: mineral material, water, air, and organic matter. While organic matter typically makes up only 5% or less of most soils, it is crucial in maintaining soil health. It serves as a primary food source for soil microbes, producing compounds that act like a natural glue. This 'glue' binds soil particles into small clumps, known as aggregates. Well-formed soil aggregates are essential because they create pore spaces that allow soil to retain moisture and oxygen—both vital for healthy root growth in all plants.
How to apply organic matter
Applying organic matter to garden soil is straightforward. For new gardens, spread 2 to 3 inches of organic matter evenly over the planting area, then thoroughly incorporate it using a broad fork or tiller to prevent layering or pockets. Adding smaller amounts (½ to 1 inch) each fall or spring can help maintain soil health and productivity in established gardens. Conducting a soil test every few years is a good way to monitor organic matter levels and ensure balanced soil fertility.
Fall is an ideal time to add organic matter since it has the entire winter to break down and integrate into the soil. However, spring applications are also practical—just be sure the soil is not too wet before tilling. If adding organic matter in the spring, opt for already well-decomposed materials, such as finished compost, aged manure, peat moss, or well-rotted leaves.
For established plantings such as trees, shrubs, and perennials, gardeners can carefully remove existing mulch, apply a one-inch layer of compost, and then replace it. This method enhances soil organic matter without disturbing existing plant roots.
If you are unsure about your soil's organic matter content, consider conducting a soil test. A soil test provides valuable information about soil pH and nutrient levels and helps determine how much organic matter is needed to optimize soil health. Visit our website at www.centralkansas.ksu.edu for more information about collecting and submitting a soil sample for testing.