“ABC’s of Soil Quality”

Improving soil quality and increasing farm

 resilience with no-till cropping systems

Susan Samson-Liebig

USDA-NRCS

2006 Manitoba-North Dakota Zero Tillage

Farmers Association Workshop

February 9, 2006

Review for today:

What is soil quality

Assessing soil quality

What lives in the soil

Organic Matter

Top 10 Reasons to no-till

What is soil quality?

Soil quality refers to the capacity

of the soil to function.

What functions do soils perform???

1. Support plants and buildings

2.   Cycle nutrients

3.   Filter water

4.   Regulate water flow

5.   Maintain productivity

Soil Quality Indicators Indirectly Measure Soil Function

Indicators used to assess

 soil function are:

       - Physical

       - Chemical

       - Biological

Tools to Measure Soil Quality:

Soil Quality Score Cards

Soil Quality Test Kit

Just Dig a hole…

Physical Indicators

Infiltration

Factors Influencing Infiltration:

• Tillage/no-till

• Pores – size and number

• Soil compaction due to field equipment

• Surface Crusting

• Biological Activity (earthworms, etc.)

• Soil structure

Aggregate Stability

Factors Affecting Aggregate Stability:

Tillage

- Glomalin Content (Soil Glue)

- Organic Matter Content

- Clay Content

- Salinity/Sodium Levels

Bulk Density

Definition:

Bulk Density is the weight of a given volume of soil.

Compaction is the reduction of pore space. 

Why is it important?

   - Root growth and development

      - Water and air movement

Soil Pores

Factors Influencing Soil Pores:

• Tillage

• Compaction

• Plants and Animals

Chemical Indicators

Soil pH

Soil Nitrate

Salinity

(Electrical Conductivity or “EC”)

Soil Biological Indicators

Life in the Soil

• Bacteria

• Fungi

• Protozoa

• Nematodes

• Arthropods

• Earthworms

For more information on soil biology, see the “Soil Biology Primer”

Organic Matter Matters!

Soil Organic Matter (SOM)
(1-6% of TOTAL soil mass)

(Alive) Living organisms 3-9% of SOM

bacteria, fungi, earthworms, nematodes,

     insects, plant roots

(Recently Dead) organic matter 7-21% of SOM

fresh or partially decomposed labile (dynamic)

(Really Dead) Humus 70-90% of SOM

     well decomposed and very stable

Soil Organic Matter results in more stable aggregates, more soil porosity, and higher infiltration rates which results in decreased erosion.

Intensive tillage destroys the biological and ecological integrity of the soil system

Products of tillage are:

Reduced organic matter

Poor aggregation (tilth) and destroyed structure

  - create a plow pan

Reduced water movement into and within the soil

Reduced nutrient cycling due to disruption of   soil biological communities

Reduced pest suppression

Reduced Soil Function

Ways to Increase Soil Quality:

• Residue Management

– Leave as much residue on and intact with the soil surface as possible.

          Result: increased OM.

• Crop Rotation

– Increase diversity of crops and plants.           

– Result: increase diversity of microbes.

• Reduce Tillage (No-Till)

– Adopt reduced tillage.

       Result: increase aggregate stability, infiltration rates, nutrient cycling potential.

Top 10 Reasons to No-till:

10. Weed control

9. Pest control/Reduced pesticide use

8. Reduced fertilizer over time

7. Increase diversity (above- and below-ground)

6. Reduced field operation/decrease compaction

5. Reduced erosion (wind and water)

4. Increased soil organic matter

3. Improved soil quality

2. Increased available water capacity

1.  Reduced input costs $$$$

“A new day in agriculture will come if, and when, we get both our hands and our minds a bit deeper into our soils.”

William A. Albrecht