Land Classification
The Soil Conservation Service uses a classification system to describe the capability of the soils to produce crops.
SCS CAPABILITY CLASSES
There are 8 SCS land capability classes. Each class is based on what the land may be used for and what is required to maintain the classification
LAND CAPABILITY CLASSES
Class I-Cultivated cropsClass II-Cultivated cropsClass III-Cultivated cropsClass IV-Cultivated cropsClass V-PastureClass VI-PastureClass VII-ForestryClass VIII-Wildlife & Recreation
FACTORS AFFECTING LAND CLASS
• Slope
• Topsoil thickness
• Erosion
• Topsoil texture
• Permeability of subsoil
• Drainage
• Effective depth
SLOPE CATEGORIESfor South Georgia
Range Land Class
Nearly level 0-2% IVery gentle 2-5% IIGentle 5-8% IIISloping 8-12% IVStrongly Sloping 12-17% VISteep >17% VIIVery Steep NA NA
TOPSOIL THICKNESS
Category Range Land Class
Extremely Thick >40” IIIVery Thick 20-40” IThick 10-20” IModerate 5-10” IThin <5” II
Topsoil thickness is measured from the soil surface to the 1st texture change.
EROSION
• The percentage of original topsoil which has eroded.
• Determined by subtracting the actual topsoil from the original and dividing the eroded by the original and multiplying by 100.
EROSION CATEGORIES
Category Range Land Class
None to slight <25% I
Moderate 25-75% II
Severe >75% III
SOIL TEXTURE
Soil is made up of 3 particles: sand, silt & clay
There are 3 categories of texture:Fine-smooth, sticky with no grit, will form a 2 inch or longer ribbonMedium-between fine & coarse, will form a ball and show some finger marks, will form a short ribbonCoarse-sandy, will not form a ribbon
PERMEABILITY OF SUBSOIL
The ability of air & water to move through the subsoil. Based on subsoil texture.
Rapid-coarse texture >20”
Moderate-medium texture subsoil
Slow-fine texture subsoil
DRAINAGE
Refers to surface & internal drainageAs a general rule, the quicker the soil can be
tilled following a good rainfall the better the drainage.
Color is the best indicator of drainageBright colors (reds & yellows) indicate good
drainageDull colors (grays & browns) indicate poor
drainage
DRAINAGE CATEGORIES
Category Looks
Excessively drained Coarse texture for over 40”
Well-drained No gray mottles in top 30”
Moderately well-drained No gray mottles in top 20”
Somewhat poorly drained No gray mottles in top 10”
Poorly drained Gray matrix or gray mottles in top 10”
Very wet Surface water
DRAINAGE LAND CLASS
Category Land Class
Excessively drained III
Well-drained I
Moderately well-drained II
Somewhat poorly drained III
Poorly drained IV
Very Wet V
EFFECTIVE DEPTH
The depth to which plant roots can easily penetrate. Usually the combined thickness of the topsoil and subsoil.
Hard pans and plow pan layers may affect root depth.
The presence of roots is a good indication of effective depth.
EFFECTIVE DEPTH RANGE
Category Range Land Class
Deep Roots over 40” I
Moderate Roots from 20-40” II
Shallow Roots from 10-20” III
Very Shallow Roots <10” IV
LAND TREATMENT PRACTICESVegetative
1. Use conserving & improving crops occasionally-Always on class I
2. Use conserving & improving crops 1/2 of time-Always on class II
3. Use conserving & improving crops 2/3 of time-Always on class III
4. Use conserving & improving crops 3/4 of time-Always on class IV
5. Prevent residue burning-Always on classes I, II, III, & IV
6. Provide mulching with crop residue-Always on classes I, II, III, & IV
7. Use strip crops-On II, III & IV if terraces are not used & D slopes if terraces are used
8. Use crop rotation-Always on classes I, II, III, & IV
9. Control weeds, bushes & trees-Always on classes I, II, III, IV, & VI
10. Establish recommended grass and/or legumes-On pasture if < 50% of the plot is covered by a desirable species
11. Improve present stand of pasture-Always on class VI when practice #10 is not used
12. Control grazing-Always on class VI
13. Fence the pasture-Always on class VI
14. Use artificial reforestation-On class VII with no trees or if stand is poor & seed trees are absent
15. Use natural reforestation-Always on class VII; applies to current & future growth
16. Use prescribed burn occasionally-Always on class VII
17. Protect trees from wildfires-Always on class VII
18. Control forest insects & diseases-Always on class VII
19. Protect trees from animal damage-Always on class VII
20.Control undesirable species-Always on class VII
21.Harvest trees by clear cutting-On VII with a mature stand or if it has merchantable trees of an undesirable species & no merchantable trees of a desirable species
22.Harvest trees by selective cutting-Always on class VII; applies to current or future growth
LAND TREATMENT PRACTICESMechanical
23.Terrace the field-On II, III & IV when slope > 2% & topsoil < 20 inches
24.Maintain field terraces-Always when #23 is used
25.Establish vegetative waterways-Always when #23 is used
26.Construct diversion terraces-On I, II, III, IV & VI if an up-slope water problem exists
27.Plow & cultivate on the contour-Always on cropland & pasture
28.Control existing gullies by special methods-Always on cropland and on pasture when present
LAND TREATMENT PRACTICESPlant Nutrients
29. Apply lime-On I, II, III, IV if pH < 6.0 & on pasture if pH < 6.5
30. Apply manure-On I, II, III, IV & pasture when available
31. Apply nitrogen-Always on classes I, II, III, IV & pasture
32. Apply phosphorus-On I, II, III, IV & VI if phosphorus is less than very high
33. Apply potash-On I, II, III, IV & VI when potash is less than very high