The Dust Bowl

• Reasons?• 100-125 Million Acres• April 14, 1935 (Black Sunday)• The Grapes of Wrath• NRCS• Conservation Methods?

Judging Land

When judging land we look at clues that tell us how well the land can produce. These clues include: soil texture, depth, slope, degree of erosion, permeability, surface runoff and flood potential

Describe Soil Texture?

• Soil texture refers to the size of the individual soil particles, called soil separates.– Sand– Silt– Clay

Sand

• Sand has the largest particles of the three soil separates.

• Feels gritty• Allows for good water

drainage.• Not usually good for growing

crops– Nutrients are washed away

easily.

Silt

• Silt is finer than sand• Feels powdery to the touch• Holds water and nutrients in the soil well,

making it a good texture for growing crops.

Clay

• Clay is the smallest soil particles.• Very hard when dry • Sticky when wet.• Don’t allow water to penetrate or drain well,

making them less desirable for growing crops.

Just how big are these soil particles?

• Sand 0.05-2.0 Millimeters• Silt 0.002-0.05 Millimeters• Clay 0.002-Lower

What makes the best soil?

• Most soils are a combination of sand, silt, and clay.

• Soils that contain a mixture of:– 52% sand– 28-52% silt– 7-27% clay

• This mixture is called a loam and is ideal for crop production.

Soil Texture Affects?

• Soil permeability– Water drains quickly through sandy soils – Water drains slowly through clay soils

• Water content • Pore size• Aeration• Root penetration

Texture Classes

• Coarse• Moderately Coarse• Medium• Moderately Fine• Fine

What is a soil profile?

• Soil profile is a vertical; cross-section of a soil that exposes all of the built-up layers it is made of. In the soil profile you can usually see distinct layers of soil. These are called soil horizons.

Soil Depth

• Soil depth is the total thickness of surface and subsoil soil that is favorable for root development.

• Depth determines: amount of water, volume of soil available for root growth, and supply of nutreints

Soil Depth

• Deep: 40 inches or greater• Moderately Deep: 20” to 40”• Shallow: 10” to 20”• Very Shallow: less than 10”

Slope

• Slope factors water runoff, erosion, and use of farm machinery.

• Slope is the percentage of rise or fall over a 100-foot horizontal distance.

• 6 slope classes are recognized in Oklahoma Land Judging (CDE)

Slope Classes

• Nearly Level: less than 1%• Gently Sloping: 1-3%• Moderately Sloping: 3-5%• Strongly Sloping: 5-8%• Steep: 8-15%• Very Steep: greater than 15%

Erosion

• Soil erosion is the detachment and movement particles.

• Factors affecting erosion are water and air movement.

• Four erosion classes are recognized.

Erosion Classes

• None to slight: less than 25% of the surface soil has been removed and no gullies are presents

• Moderate: 25-75% of the original surface soil is present. May have crossable gullies.

• Severe: more than 75% of the original surface soil has been removed. May have crossable gullies.

Erosion Classes

• Very Severe: more than 75% of the original surface soil has been removed. Uncrossable gullies are present.

• Uncrossable Gullies: 6 inches deep X 12 inches across

Permeability

• Refers to the movement of air and water through the soil profile.

• Subsoil Texture Permeability classes

Rapid- coarse textureModerate- moderately coarse/ mediumSlow- moderately fineVery- fine

Surface Runoff

• Rate water is removed off the soils surface.• Slope

Surface Runoff classesRapid-greater than 3% Moderate- 1-3%Slow- 0-1%Very Slow- coarse texture subsoils

Land Capability Classes

• I - suited cultivation, no limitations• II• III• IV• V - frequent flooding/ poor drainage• VI - grazing • VII - grazing• VIII – wildlife / recreaction

Land Capability Class

• Classes I-IV are considered Cultivated

• Classes V-VIII are considered Non-Cultivated

Recommended Land Treatments

• Vegetative

• Mechanical

• Fertilizer and Soil Amendments

Field Card