Organic matter: It matters!

Organic matter is recognized as being important and there are many reasons why.

Organic matter is openly recognized as a valuable part of our soils, however, the reasons why aren’t always fully recognized. Understanding why organic matter matters is just another component in better understanding and managing your soil health.

Organic matter is comprised of multiple fractions or pools each of which benefits and contributes to soil health in different ways. The active fraction of organic matter has the fasted breakdown or turnover rate of approximately one to two years. Lasting longer than the active fraction, approximately two to five years is the intermediate fraction. The third pool is the stable fraction, which is more resistant to break down and can take 10 or more years to breakdown.

While there are many ways that organic matter contributes to soil health, these benefits can be categorized into a few general categories: nutrient cycling, water movement, and soil structure. When we maintain or increase the organic matter portion of the soil, we gain the following benefits.

Nutrient cycling benefits

  • Increases supply of plant nutrients upon organic matter breakdown
  • Increased storage of nutrients with increased Cation Exchange Capacity

Water movement

  • Increased water holding capacity
  • Reduced runoff
  • Improved water infiltration
  • Decreased soil water evaporation

Structure

  • Reduced soil crusting especially in fine-textured soils
  • Improved aggregation reducing soil erosion
  • Increased compaction resistance
  • Improved root development and infiltration

For information on how to build your organic matter levels, see the follow-up MSU Extension News for Agriculture article, Organic matter: Build it up!.

For more information on organic matter and the benefits of organic matter, see Building Soil Organic Matter with Organic Amendments from the University of Wisconsin-Madison, or the Organic Matter Soil Management Series from the University of Minnesota Extension.

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