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LAND JUDGING. Land Classification. The Soil Conservation Service uses a classification system to describe the capability of the soils to produce crops. SCS CAPABILITY CLASSES.
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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 crops Class II-Cultivated crops Class III-Cultivated crops Class IV-Cultivated crops Class V-Pasture Class VI-Pasture Class VII-Forestry Class 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% I Very gentle 2-5% II Gentle 5-8% III Sloping 8-12% IV Strongly Sloping 12-17% VI Steep >17% VII Very Steep NA NA
TOPSOIL THICKNESS Category Range Land Class Extremely Thick >40” III Very Thick 20-40” I Thick 10-20” I Moderate 5-10” I Thin <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 ribbon Medium-between fine & coarse, will form a ball and show some finger marks, will form a short ribbon Coarse-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 drainage As a general rule, the quicker the soil can be tilled following a good rainfall the better the drainage. Color is the best indicator of drainage Bright colors (reds & yellows) indicate good drainage Dull 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 • Use conserving & improving crops occasionally-Always on class I • Use conserving & improving crops 1/2 of time-Always on class II • 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 • Use strip crops-On II, III & IV if terraces are not used & D slopes if terraces are used • 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
Use artificial reforestation-On class VII with no trees or if stand is poor & seed trees are absent • Use natural reforestation-Always on class VII; applies to current & future growth • Use prescribed burn occasionally-Always on class VII • Protect trees from wildfires-Always on class VII • Control forest insects & diseases-Always on class VII • Protect trees from animal damage-Always on class VII
Control undesirable species-Always on class VII • 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 • Harvest trees by selective cutting-Always on class VII; applies to current or future growth
LAND TREATMENT PRACTICESMechanical • Terrace the field-On II, III & IV when slope > 2% & topsoil < 20 inches • Maintain field terraces-Always when #23 is used • Establish vegetative waterways-Always when #23 is used
Construct diversion terraces-On I, II, III, IV & VI if an up-slope water problem exists • Plow & cultivate on the contour-Always on cropland & pasture • Control existing gullies by special methods-Always on cropland and on pasture when present
LAND TREATMENT PRACTICESPlant Nutrients • Apply lime-On I, II, III, IV if pH < 6.0 & on pasture if pH < 6.5 • Apply manure-On I, II, III, IV & pasture when available • Apply nitrogen-Always on classes I, II, III, IV & pasture • Apply phosphorus-On I, II, III, IV & VI if phosphorus is less than very high • Apply potash-On I, II, III, IV & VI when potash is less than very high