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CHAPTER 4: Soil Survey, classification and evaluation
4.1 SOIL SURVEY•Introduction of Soil Survey•Stages in Soil Survey Program•Types of Soil Survey•Steps in Soil Survey•Land Capability Classification
• Soil Survey = the process of classifying soil types and other soil properties in a given area and geo-encoding such information
• published results of soil survey activities
Steps in Soil Survey Program
Stage 1: Pre-Field Activities
Stage 2: Field Survey
1. Soil Mapping
2. Evaluation and Field activities
Stage 3: Post-Field Activities
Kinds of Soil Survey
• Reconnaissance Surveys
• Detailed Special Surveys
• Special Purpose Surveys
Step 1: Delineating Soil Unit
• Delineating soil unit with respect to topography
• determination of texture
• Determination of slope – Erosion phases
• Vegetation
- video
Step 2: Soil Sampling
• 2 types:
• a) Free Survey
- As many as necessary samples are taken within the boundaries
b) Grid Survey
- Transverses and transect s are laid out in a grid pattern, samples are taken at every intersect. Distance between lines: 50 meter
Draw both types of Surveys Maps
3. Profile Sampling
• Profile pit is dug to C or R horizon
• 120 to 200 cm if regolith extend beyond 200 cm
• Pit size is enough for a person to go down and turn around
• Expensive & Labour Intensive
• Use Core sampler
• Cheaper and easier
• Fill the profile description form
• Expressing the physical phases of soil
- Soil Texture
- Soil Structure
- Soil Consistence/Soil Strength
- Soil Color
- Soil Permeability
- Soil Temperature
Step 4: Plotting the Soil Mapping Unit
• Collaborating analytical data are coded in term of soil types, phases (stoniness and erosion) and slope.
Step 5: Correlation
• Previous profile study
• if the profile under study indicates very close similarities with an established profile existing in another place the soil under study is name after the other soil
Step 6: Soil Mapping • Preparing scaled map showing all soil unit investigated
Step 7: Soil Survey Report
• The report embodies all items in the soil survey program
Step 8: Land Capability Classification
• refers to the productive capacity of the soil for intensive as influence by soil fertility, moisture supply and depth of solum
• 2 main points land capability
a) soil limitation -soil physical aspect that restrict crop production
b) climatic limitation - adverse climatic problem
QUESTIONS AND DISCUSSION?
4.2 SOIL CLASSIFICATIONIntroduction to Soil Classification
• grouping soils by their intrinsic property (soil morphology), behavior, or genesis, results in classes that can be interpreted for many diverse uses.
• No universally accepted classification system
• Based on field: Agriculture, Engineering, OSHA
• Lead to confusion
Most common for Agriculture :
US Soil Taxonomy (1975)
FAO/UNESCO Soil Classification (1974)
FAO Soil Classification
• first published in form of the UNESCO Soil Map of the World (1974)
• Many of the names offered in that classification are known in many countries and do have similar meanings.
• Many countries modified this system to fit their particular needs.
• Soil Units form 26 World Classes.
• intended for mapping soils at a continental scale but not at local scale.
• developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters (most commonly their properties) and in 7 levels; Order >> Suborder >> Great Group >> Subgroup >> Family >> Series.
• 12 orders
12 Orders of Soils (USDA)
• alfisols
• aridisols
• gelisols
• inceptisols
• oxisols
• ultisols
• andisols
• entisols
• histosols
• mollisols
• spodosols
• vertisols
Example of USDA Taxonomy
4.3 LAND EVALUATIONIntroduction to Land Evaluation
• the process of valuing real property (usually market value).
• requires appraisals because they occur infrequently and every property is unique (especially their location, a key factor in valuation)
• Land Appraisal consists 2 phases: a) land characterization b) socio-economy aspect