Land Evaluation and Classification Kevin Jump Bleckley County High School Compiled from the Land Judging Contest Guide originally prepared by Dr. Frank.

Land Evaluation and ClassificationLand Evaluation and Classification

Kevin JumpBleckley County High School

Compiled from the Land Judging Contest Guide originally prepared by Dr. Frank Flanders

Land Capability ClassesLand Capability Classes

There are eight land capability classes. Each class has the same meaning in all parts of the United States. A description of the eight land capability classes and their most intensive use are in the following slides.

Class IClass I

Soils in Class I have very few limitations which restrict their use. They may be used for the production of cultivated crops.

Class IIClass II

These soils may also be used for cultivated crops but they have some limitations that require moderate conservation practices.

Class IIIClass III

Class III land has severe limitations that require special conservation practices and may reduce the choice of crops.

Class IVClass IV

These soils are used for cultivated crops but have very severe limitations that restrict the choice of plants and require special management.

Class VClass V

These soils usually appear in small and nearly level drainage ways. They are not subject to erosion but have limitations such as frequent flooding and wetness which make them unfit for cultivation. Class V is used for pasture.

Class VIClass VI

These soils have such severe limitations that they are unsuited to cultivated crops and are restricted to pasture, woodland, or wildlife feed and cover.

Class VIIClass VII

These soils have very severe limitations and their use is restricted to forestry and wildlife.

Class VIIIClass VIII

This soil is so severely limited that its use is devoted entirely to wildlife, water supply, recreation or aesthetic purposes.

Factors Affecting Land ClassFactors Affecting Land Class

Slope Topsoil Thickness Erosion Topsoil Texture Permeability of Subsoil Drainage Effective Depth

SlopeSlope

Steepness of the field Rise over run Determined by the amount of fall in feet per 100

feet Expressed in percent

Slope CategoriesSlope CategoriesCategories South Georgia N Georgia

1. Nearly Level 0 – 2% 0 – 2%2. Very Gentle 2 – 5% 2 – 6%3. Gentle 5 – 8% 6 – 10%4. Sloping 8 – 12% 10 – 15%5. Strongly Sloping 12 – 17% 15 – 25%6. Steep Over 17% 25 – 60%7. Very Steep N/A Over 60%

Slope – Best Land ClassSlope – Best Land Class

1. Nearly Level I2. Very Gently II3. Gentle III4. Sloping IV5. Strongly Sloping VI6. Steep VII7. Very Steep VII

Topsoil ThicknessTopsoil Thickness

Surface layer of land Determined by depth to texture change Topsoil usually darker Color can indicate the dividing line but not

always

Topsoil Thickness CategoriesTopsoil Thickness Categories

1. Extremely Thick over 40 inches2. Very Thick 20 to 40 inches3. Thick 10 to 20 inches4. Moderate 5 to 10 inches5. Thin less than 5 inches

Topsoil Thickness – Best Land ClassTopsoil Thickness – Best Land Class

1. Extremely Thick III2. Very Thick I3. Thick I4. Moderately Thick I5. Thin II

ErosionErosion

Percent of original topsoil which has eroded At the CDE the original topsoil thickness will be

listed on the assumption card Calculate by dividing the amount of topsoil that

has eroded by the original topsoil thickness

Erosion CategoriesErosion Categories

None to Slight less than 25% eroded Moderate 25 to 75% eroded Severe over 75% eroded

Erosion – Best Land ClassErosion – Best Land Class

1. None to Slight I2. Moderate II3. Severe III

Topsoil TextureTopsoil Texture

Determined by soil particle size in the topsoil Sand is the largest Clay is the smallest Determined by feel using water

Soil Texture TriangleSoil Texture Triangle

Topsoil Texture CategoriesTopsoil Texture Categories

Fine smooth and sticky when wet – like flour

Medium mixture of sand, silt and clay – like salt and flour

Coarse mostly sand particles – like salt

Topsoil Texture – Best Land ClassTopsoil Texture – Best Land Class

1. Fine I2. Medium I3. Coarse I

Permeability of SubsoilPermeability of Subsoil Ability of air and water to move through the subsoil Primarily due to soil texture Based on texture except when topsoil exceeds 20

inches When the topsoil depth exceeds 20 inches the subsoil

permeability plays a minor role in crop production In these cases permeability will be based on the texture

of the top 20 inches

Subsoil Permeability CategoriesSubsoil Permeability Categories

1. Rapid Coarse texture2. Moderate medium texture3. Slow fine texture

Permeability of Subsoil – Best Land ClassPermeability of Subsoil – Best Land Class

1. Rapid II2. Moderate I3. Slow II

DrainageDrainage

Refers to surface and internal drainage (water movement)

Best clue is color which is determined mostly by iron compounds

Well drained – rusty Poorly drained - gray

Drainage CategoriesDrainage Categories1. Excessively drained – coarse textured, sandy

material that continues to depths of more than 40 inches

2. Well drained – No gray mottles in top 30 inches3. Moderately well drained – no gray mottles in top 20

inches4. Somewhat poorly drained – no gray mottles in top 10

inches

Drainage Categories (cont.)Drainage Categories (cont.)

5. Poorly drained – Gray matrix or gray mottles found in top 10 inches

6. Very Wet – surface water remains for extended periods

Drainage – Best Land ClassDrainage – Best Land Class

1. Excessively drained III2. Well drained I3. Moderately well drained II4. Somewhat poorly drained III5. Poorly drained IV6. Wet V

Effective DepthEffective Depth

Depth to which plant roots can easily penetrate and absorb water and nutrients

Usually the combined thickness of topsoil and subsoil

Root penetration may be restricted by rock layers, hardpans and plow pan layers

Effective Depth CategoriesEffective Depth Categories

1. Deep over 40 inches2. Moderate 20 to 40 inches3. Shallow 10 to 20 inches4. Very Shallow Less than 10 inches

Effective Depth – Best Land ClassEffective Depth – Best Land Class

1. Deep I2. Moderate II3. Shallow III4. Very Shallow IV