Guidelines: Land evaluation for irrigated agriculture - FAO soils bulletin 55

Table of Contents

Soils Resources, Management and Conservation Service
FAO Land and Water Development Division

Rome, 1985

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ISBN 92-5-102243-7

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© FAO 1985

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Table of Contents



Part one - Procedures for evaluating land for irrigated agriculture

1. Introduction

1.1 General
1.2 From project identification to project implementation
1.3 Levels of intensity of investigations
1.4 Planning a land evaluation investigation

2. Evaluating and classifying land for irrigated agriculture

2.1 Basic principles
2.2 Terminology
2.3 Main procedures in land evaluation and classification

2.3.1 Need for preliminary studies
2.3.2 Identification of relevant land utilization types
2.3.3 Inventory of land resources
2.3.4 Selection of class-determining factors
2.3.5 Classification of 'provisionally-irrigable' land and 'irrigable' land

2.4 Land productivity index and economic measures of suitability

3. A step-by-step guide to the procedures

3.1 List of main steps

4. Deciding the land utilization types to evaluate and developing the land suitability class specifications

4.1 Deciding and describing the land utilization types to evaluate

4.1.1 Examples of irrigated LUTs
4.1.2 Some problems in defining and describing LUTs

4.2 Developing the land suitability class specifications

4.2.1 Steps in developing the land suitability class specifications
4.2.2 Class-determining factors (step 3)
4.2.3 Land use requirements and limitations
4.2.4 Critical limits of 'class-determining' land use requirements and limitations

5. Procedures for land resource inventory

5.1 General characterization of the project area
5.2 Topographic data
5.3 Soil survey data
5.4 Climatic and meteorological data
5.5 Water resources data
5.6 Drainage data
5.7 Present land use, vegetation and wildlife
5.8 Environmental health
5.9 Social and economic data

5.9.1 Social and economic considerations
5.9.2 Checklist of socio-economic data

6. Assigning the land suitability classes by matching

6.1 Determining the factor ratings
6.2 Interactions between the factors
6.3 Evaluating 'significance' in combining factor ratings
6.4 Symbols for summarizing land suitability class and subclasses
6.5 An example of the use of the formats
6.6 Incorporating crop yield data and costs

7. Economic evaluation of land suitability for irrigation

7.1 Terminology
7.2 Budgeting for comparisons of returns
7.3 Use of costs and benefits in determining land suitability class

7.3.1 Establishing the cut-off between suitable and not suitable land
7.3.2 Establishing the range of permissible area-specific land development costs
7.3.3 Nomograph for quick determination of NIIB

7.4 Final selection of LUTs for the 'irrigable' land
7.5 Confirming financial viability from the farmers' viewpoint

8. Presentation of the results

8.1 Reconnaissance level studies
8.2 Pre-feasibility and feasibility studies

8.2.1 Form of report

9. The role of land evaluation in project appraisal and implementation

9.1 Feasibility appraisal
9.2 Project implementation and monitoring

10. The US bureau of reclamation land classification system

10.1 Principles
10.2 USBR terminology
10.3 Financial and economic considerations
10.4 Land classes and subclasses of the USBR system
10.5 the USBR mapping symbols
10.6 USBR land classification specifications

Part two - Developing the specifications and critical limits of class-determining factors

A. Agronomic factors

A.1 Growing cycle and growing period

A.1.1 Critical limits of growing period

A.2 Radiation
A.3 Temperature
A.4 Rooting
A.5 Aeration
A.6 Water quantity

A.6.1 The significance of water quantity as a class-determining factor
A.6.2 Water requirement in relation to water supplies
A.6.3 Crop yields and water stress
A.6.4 Estimating irrigation and crop water requirements
A.6.5 The contribution of rainfall to water requirements in farmers fields (effective rainfall)
A.6.6 Seepage and percolation in wetland rice

A.7 Nutrients (NPK)

A.7.1 Nitrogen
A.7.2 Phosphorus
A.7.3 Potassium
A.7.4 Factor rating 'NPK nutrition'

A.8 Water quality
A.9 Salinity
A.10 Sodicity
A.11 pH, micronutrients and toxicities

A.11.1 pH, micronutrient deficiencies and toxicities on non-rice cropland
A.11.2 Chemical characteristics of submerged rice soils (based on Ponnamperuma 1976)
A.11.3 Acid sulphate soils

A.12 Pests, diseases and weeds
A.13 Flood, storm, wind and frost

A.13.1 Flooding in rice cultivation
A.13.2 Flood hazard
A.13.3 Storm, hail and wind hazard
A.13.4 Frost hazard

B. Management

B.14 Location
B.15 Water application management
B.16 Pre-harvest farm management
B.17 Harvest and post-harvest conditions
B.18 Mechanization

C. Land development and land improvements

C.19 Land clearing

C.19.1 Forested areas
C.19.2 Areas of persistent weeds
C.19.3 Removal of rocks and stones

C.20 Flood protection
C.21 Drainage
C.22 Land grading
C.23 Physical, chemical and organic aids and amendments

C.23.1 Physical aids to reclamation such aids include:
C.23.2 Chemical and organic amendments

C.24 Reclamation leaching
C.25 Duration of the reclamation period
C.26 Irrigation engineering requirements

D. Conservation and the environment

D.27 Long-term prevention of salinity and sodicity hazards
D.28 Control of groundwater and surface water
D.29 Long-term erosion hazard
D.30 Other environmental hazards

E. Socio-economic factors

E.31 Farmers' attitudes to irrigation
E.32 Other socio-economic factors

Appendix 1 - The structure of the FAO framework classification

Appendix 2 - Discounted present value 1/

Appendix 3 - Comparison of criteria for investment analysis: Farm financial analysis vs project economic analysis



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