LandJudging in Oklahoma

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 content Pore size 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 texture Moderate- moderately coarse/ medium Slow- moderately fine Very- fine

Surface Runoff Rate water is removed off the soils surface. Slope Surface Runoff classes Rapid-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

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