Getting Down and Dirty With Soil Developed by : Hudson Minshew, Oregon State University Extension Service Susan Donaldson, University of Nevada Cooperative Extension USDA NRCS

What you’ll learn today  Soil texture and structure  The living soil  Understanding soil erosion  Reducing soil erosion  Improving your soil  Taking a soil sample NRCS, Mont.

What describes a good soil?  Drains well  Doesn’t crust after planting  Soaks up heavy rains with little runoff  Stores moisture for drought periods  Has few clods and no hardpan  Resists erosion and nutrient loss  Produces healthy, high quality crops

NRCS, Mont. Soil is a foundation for:  Growing plants and crops  Supporting buildings, roads and bridges  Housing a septic system  Storing and filtering water

How are soils formed? A. Miller

Soil horizons USDA NRCS

Compare horizons OSU Extension Service

What are soils made of?  Minerals  Air  Water  Organic matter (humus)

Soil minerals A. Miller

Water = 20-30% Air = 20-30% Mineral fraction (sand, silt, clay) = 45-50% Organics = 0-5% Composition of a loam soil

The soil textural triangle A. Miller

NRCS, Bozeman Mont. Textural triangle for the graphically challenged

Texture by feel: Sand Adapted from NRCS, Bozeman Mont. by A. Miller

Texture by feel: Loamy sand Adapted from NRCS, Bozeman Mont. by A. Miller

Texture by feel: Loams and clays Adapted from NRCS, Bozeman Mont. by A. Miller

Why determine soil texture? Soil texture influences:  Water intake rates  Water-storage capacity  Ease of tillage  Amount of aeration  Soil fertility

In this experiment, an equal amount of water was applied to three soil types. NRCS, Bozeman, Mont. Soil texture affects drainage

Note the amount of water that drained from the sandy loam soil. NRCS, Bozeman, Mont. Soil texture affects drainage

Less water has drained from the silty clay loam soil. Soil texture affects drainage NRCS, Bozeman, Mont.

The loam soil drained almost as much as the sandy loam. Soil texture affects drainage NRCS, Bozeman, Mont.

Platy structure Granular structure Soil structure: How particles are grouped together into stable collections

OSU Extension Service Good quality soil has:  Good aeration  Good drainage  Good tilth, meaning they’re easy to work  Lots of organic matter  Lots of organisms

USDA NRCS The living soil

worm USDA NRCS

Soil organic matter consists of:  Living organisms  Dead organisms  Plant matter  Other decomposing organic materials UNCE, Reno, Nev.

Benefits of soil organic matter  Increased water- and nutrient- holding capacity  Formation of soil into stable aggregates  Reduced soil compaction  Improved water infiltration

What threatens my soil? NRCS, Bozeman, Mont.

Water drop impact USDA NRCS

 Sheet  Rill  Gully Types of water erosion A. Miller

Severe water erosion occurred during the “dust bowl” era in the 1930s USDA NRCS Photo Gallery

Signs of water erosion  Small rills and channels on the soil surface  Soil deposited at the base of slopes  Sediment in streams, lakes, and reservoirs  Pedestals of soil supporting pebbles and plant materials

Erosion Note both compaction and rill erosion OSU Extension Service

Gully erosion OSU Extension Service

Damage from erosion can cause loss of property and jeopardize safety NRCS, Bozeman, Mont.

Streambank erosion UNCE, Reno, Nev.

NRCS, Bozeman, Mont. Wind erosion

NRCS, Bozeman, Mont. Wind erosion NRCS, Bozeman, Mont.

How to reduce soil erosion  Use common sense  Retain existing vegetation whenever possible, or add protective cover such as cover crops or mulch and plant litter  Time grading, construction and tillage to minimize exposure of soil to erosive forces

How to reduce soil erosion  Fit development to the terrain  Divert runoff away from bare areas  Create a barrier to the erosive agent  Keep runoff velocities low

How to reduce soil erosion  Minimize length and steepness of slopes  Trap sediment on-site  Reduce tillage and number of passes  Maintain drainageways to handle increased runoff

Use a buffer strip between water’s edge and cultivated or grazed land to help catch soil particles that may erode. USDA ARS

Ungrazed or unharvested buffer strips OSU Extension Service  Create barriers  Reduce velocities  Trap sediment

OSU Extension Service  Minimize length and steepness of slopes  Slow runoff velocities  Increase infiltration Contours and terraces

OSU Extension Service Sometimes the solution involves engineering

Overgrazing and letting water run across the disturbed ground is a surefire way to increase erosion Conservation District, Bozeman, Mont.

Plant windbreaks to decrease soil loss from wind erosion NRCS, Bozeman, Mont.

Soil quality  An assessment of the capacity of a soil to: –Sustain plant and animal productivity –Maintain or enhance water and air quality –Support human health and habitation

Soil quality  Soils vary naturally in their capacity to function, so soil quality is specific to each type of soil  Soil quality is the dynamic quality of the soil. Soil quality is affected by management, such as increasing organic matter (increases quality) or tilling when wet (decreases quality)

How can I manage my soils to improve them?  Avoid compaction by: Reducing tillage of wet soils Reducing traffic on wet soils  Increase the organic matter content by: Adding compost and manure Growing and tilling in cover crops (green manure)  Maintain cover with vegetation

Avoid walking or driving on wet soil OSU Extension Service

Composition of a compacted soil Note the reduced air space in a compacted soil. BeforeAfter 70% 50%

Add soil organic matter OSU Extension Service

Manure spreaders make the job of applying manure as an organic matter amendment easier OSU Extension Service

Add compost OSU Extension Service

Household vegetable debris and grass clippings can also be used to make compost UNCE Reno, Nev.

Cover crops OSU Extension Service

How do I know what to add to my soil??? A. Miller

Test your soil! UNCE, Reno, Nev.

What information does a soil test provide?  Soil textural analysis  pH and salts  Soil nutrient content  Fertilizer recommendations

A fertile soil has:  The right kinds and amount of nutrients to grow pasture or crops  Low salinity and sodium  Close to a neutral pH (about 7)  Plenty of organic matter USDA NRCS

How often should I take a soil sample?  Prior to seeding a pasture  At least every 3 years for established pastures  Frequently enough to make good decisions on fertilization  When it is cost effective

How to take a sample First, select the site. Your soil sample should represent only one soil type or soil condition. OSU Extension Service

Each sample should consist of sub-samples taken from about 15 locations within the same soil type or sampling area. OSU Extension Service How to take a sample

Use the “slice” method for a representative sample. UNCE, Reno, Nev. How to take a sample

Summary  Know your soil texture  Remember that the soil is a living system and you need to support that environment  Erosion is costly - protect your soil with vegetation or mulches

Summary  Continually improve the soil quality by adding organic matter and practicing conservation management techniques  Use soil tests to determine whether your soil has the necessary nutrients for good productivity

Homework  Determine soil texture at several locations on your property by the look-and-feel method.  Survey your property for signs of erosion. Can you design solutions?  If you have not done so recently, submit a soil sample to a laboratory. The results will be used in other classes.