Soil Survey, Classification and Evaluation

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

4.2 SOIL CLASSIFACTION•Soil Classification Systems•Soil Classification Scheme

4.3 LAND EVALUATION

4.1 SOIL SURVEYIntroduction to Soil Survey

• 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.

26 Classes of Soil (FAO/UNESCO)

• Acrisols• Andosols• Arenosols• Cambisols• Chernozems• Ferralsols• Fluvisols• Gleysols• Greyzems• Gypsisols• Histosols• Kastanozems• Lithosols

• Luvisols• Nitosols• Phaeozems• Planosols• Podzols• Podzoluvisols• Rankers• Regosols• Rendzinas• Solonchaks• Solonetz• Vertisols• Yermosols

USDA Soil Taxonomy

• 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

The End