Soil Resources

Organic Matter

Organic matter, or more specifically soil carbon, has the most widely recognized influence on soil quality. It is tied to all soil functions. It affects other indicators, such as aggregate stability (physical indicator), nutrient retention and availability (chemical indicator), and nutrient cycling (biological indictor); and is itself an indicator of soil quality.

To maintain soil’s quality and organic matter, the Bureau of Land Management (BLM) works to reduce or eliminate soil disturbance, and leaves plant residues for cover. Disturbance stimulates erosion, breaks up soil aggregates and results in the loss of organic matter. Minimizing soil disturbance, ensuring soil cover, and controlling traffic can improve organic matter and respiration.

There is more than just one kind of organic matter. Organic matter is actually a diverse bunch of compounds, many which have not been identified.

Active organic matter (less than 1/5 of total organic matter) contains a myriad of living organisms and materials they use as food. When these organisms “eat” the organic matter (and each other) they release plant nutrients such as nitrogen (N), sulfur (S) and phosphorus (P) as well as micronutrients. Disturbances and associated clearing of vegetation leads to the loss of active organic matter and thus reduction in soil quality.

Passive organic matter is protected from microorganisms because it is chemically too hard to “digest” or is tucked away inside soil aggregates where even tiny bacteria cannot get at it. It turns over very slowly, so it does little to release nutrients or increase microbial activity. Passive organic matter acts much like a sponge, holding water, and is a long-term storage for nutrients.


Topics

Soils and Ecosystem Stability
·Soil Indicators and Function
·Soil Quality Assessment
·Soil Management
·Soil Issues
·BLM Authorized Management Activities Affecting Soil
·Organic Matter

Using the Web Soil Survey
Soils and Vegetation
·Ecological Sites and Ecological Site Descriptions (ESDs)
·State and Transition Model (STM)
·STM Example
·STM Application and Use
Restoration and Recovery