The Principles and Purpose of Soil Survey

 

The Principles and Purpose of Soil Survey

INTRODUCTION

In any country that has developed a soil survey report or soil map, the control of soil surveys is usually the responsibility of an agency (such as the Ministry of Agriculture) e.g. is the United State Department of Agriculture (USDA). A Memorandum of Understanding is reached between the controlling agency and other agencies that may have interest in the conduct of surveys or may wish to participate in a given soil survey. The publication of soil survey reports, including maps, in a standard series guides against the loss or misplacement of important soil survey information and usually a part of the soil survey programme. The practical purpose of soil survey is to enable more numerous, more accurate and more useful predictions to be made for specific purposes than could have been made otherwise i.e., in the absence of location-specific information about soils. To carry out a soil map, the units to be mapped are usually properly defined. Mapping may be carried out directly if the purpose of the survey is narrowly specific while soil properties relevant the purpose  are known.

If, however, the purpose is broad, then the soils are usually classified and mapped according to observable properties such as morphology, while other properties are measured as representative sample of each morphological group.

 

Steps that will enhance the achievement of the purpose of soil survey are:

·        Determine the pattern of the soil cover.

·        Divide this pattern into relatively homogeneous units.

·    Map the distribution of these units, so enabling the soil properties over any area to be predicted.

·    Characterize the mapped units in such a way that useful statements can be made about their land use potential and response to changes in management.


 Important Facts to know

·   There is a need to expand the work of the laboratory so that certain investigations of special importance to the soil survey can be made.

·        In the face of conflicts over potential land use, soil surveys at various levels may be needed to provide pertinent information about the comparative suitability of the kinds of soils for farming, range, forestry, housing

·      Priorities for soil survey areas require consideration of factors such as the acuteness of the need for soils information

·      Training of local personnel at various levels to carry out all phases of soil surveys should be regarded as a continuing part of the long-term programme.

·             The purpose of soil survey is both fundamental and applied

 

The Principles of Soil Survey

1. Draws heavily form soil properties: Soil survey works usually include clay mineralogy and certain phases of soil chemistry and physics, as well as information on improved methods for the dispersion of tropical clays; the cation exchange capacity of clay fractions; the mineralogy of soil horizons; the infiltration, movement, and availability of water in different kinds of soils; thin sections and the behaviour of nutrients.

2. Provision of vital information: In the face of conflicts over potential land use, soil surveys at various levels may be needed to provide pertinent information about the comparative suitability of the kinds of soils for farming, range, forestry, housing, etc. It may be advisable to contract for some of this work with outside sources, as long as the standards of mapping adopted by the Soil Survey Unit are followed so that the survey will contribute to the long-range soil survey programme.

3. Need for soil information: Priorities for soil survey areas require consideration of factors such as the acuteness of the need for soils information, the benefits to be derived, the number of people involved and their ability to make direct use of the information, and the problems faced by the soil survey team. It is suggested that the responsibility for decisions on these priorities be assigned to the proposed Land Use Committee.

4. Training: Training of local personnel at various levels to carry out all phases of soil surveys should be regarded as a continuing part of the long-term programme. This can be achieved through fellowships and attendance of soil conferences.

5. Approximations: The 7th Approximation scheme of soil classification appears to be the most satisfactory system of soil classification to use because the categories are defined precisely, and yet there is flexibility to permit a change if they are needed.

6. Correlations: The results of fertilizer applications need to be correlated with the kinds of soil on which they were made so that the information will have wider application through the use of the subsequent soil maps.

 
The Purpose of Soil Survey

The practical purpose of soil survey is to enable more numerous and accurate prediction to be made about soils. In order to achieve the purpose of soil survey, it is necessary to know the type and patterns of soil cover as well as determine its types in a relatively homogenous unit. This will guarantee the proper mapping of the distribution of the units and accurate prediction of soil properties of the studied soils. The mapped soils will also be adequately characterized in such a way that useful statements can be made about the potentials of such soils in terms of land use and response to any change in management. The purpose of soil survey is both fundamental and applied.

Fundamental: Soil surveys help in expanding our knowledge and understanding of different soils, as regards their properties, genesis, and classification for sustainable development are concerned.

Applied: Soil surveys and soil maps for the sole purpose of making predictions about the behavior of different soils for agriculture, forestry, engineering, urban development, recreation, etc., the following are the applied purpose of soil survey;

1. Transferring technology by correlating the characteristics of soils of known behavior and predicting their adaptability to various use and productivity under set of management practices. These predictions can also be used to make practical recommendations for the management of degraded soils.

2. Providing information needed for developing optimum land use plans and for bringing new areas under irrigation and drainage networks. They also help in evaluating suitability of soils for irrigation and or agricultural crops and a variety of other uses.

3. Delineating the degraded soils, such as saline alkali, waterlogged or flood prone, water and wind eroded and so-called wastelands and in suggesting soil and water conservation measures, to ameliorate these soils.

4. Land settlement, rehabilitation, tax appraisal, locating and designing highways, airports and other engineering structures and in public sanitation's works.

5. Delineating disease-infested areas and may provide indirect help in controlling the diseases, for instance, delineating schistosomiasis disease infested areas in South East Asia. The zinc deficiency in human beings, especially children, has been related to its deficiency is sandy soils of Punjab (India).

6. In short, soil surveys add to the growing wealth of knowledge about the soils of a country for developing and optimizing land use of an area.

 

Soil survey report will help the pedologist in the following areas;

·          To classify soils into well-defined mapping units i.e. soil series, phases etc.

·          To shows their distribution in the field on the map.

·          To find out the best use of soils.

·         To predict their performance under different management practices i.e. yields of crops under different management practices.

 

Special-purpose and general-purpose soil surveys

Special purpose surveys: for a single well-defined objective. The classic example is an irrigation project. Another example is conservation-oriented farm planning. The advantage of a special-purpose survey is that we know the properties of interest for the special purpose and can concentrate on mapping these, so that the mapping is more rapid and can be done with less-skilled mappers (i.e., not just trained pedologists). But, we may not record properties that are vital for other uses. Example: Brazilian system for directly mapping the physical environment.

General purpose surveys: provide the basis for a variety of interpretations for various kinds of uses, present and future, including some we can’t anticipate now. The advantage is that the survey can be re-used for many purposes. The disadvantage is that the survey isn’t ideal for any purpose; also we may not anticipate future needs. Example: ‘general purpose’ surveys pre-1970 applied to ground-water contamination studies. The trend has been towards general-purpose surveys, sponsored on a ‘speculative’ basis coordinated by a national mapping agency (e.g., in the USA, the Soil Conservation Service has formed a National Cooperative Soil Survey).However in countries with less  resources and immediate needs, the special purpose survey prevails.


CONCLUSION

Soil survey works usually include clay mineralogy and certain phases of soil chemistry and physics, as well as information on improved methods for the dispersion of tropical clays; the cation exchange capacity of clay fractions; the mineralogy of soil horizons; the infiltration, movement, and availability of water in different kinds of soils; The purpose of soil survey is both fundamental and applied. Special purpose surveys are for a single well-defined objective. General purpose surveys provide the basis for a variety of interpretations for various kinds of uses, present and future, including some we can’t anticipate now.  

In the face of conflicts over potential land use, soil surveys at various levels may be needed to provide pertinent information about the comparative suitability of the kinds of soils for farming, range, forestry, housing. Priorities for soil survey areas require consideration of factors such as the acuteness of the need for soils information. Training of local personnel at various levels to carry out all phases of soil surveys should be regarded as a continuing part of the long-term programme. The purpose of soil survey are both fundamental and applied.

Also read on: << Definition and Description of Soil Survey>>

 

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