Soil Survey

Soil Survey involves determination of soil types of an area in the field and showing their distribution in maps. Soil survey work thus includes the following functions: (a) traversing an area and estimating the types of soils on the basis of a field legend; (b) study of soil morphology in the field; (c) collection of soil samples for laboratory analyses; (d) characterisation of soils on the basis of morphological and laboratory properties; (e) classifying and correlating soils according to the international soil classification systems; (f) mapping the soil units with a suitable scale, and (g) preparing the soil survey report with interpretation.

In short, the purpose of soil survey is to identify different soils, to describe and to map them and also to evaluate their properties in relation to landuse and management.

There are four types of soil survey: (i) exploratory, (ii) reconnaissance, (iii) detailed reconnaissance, and iv) detailed survey. For each kind of soil survey specific types of base maps with suitable scale are needed. Among the types of base maps aerial photographs are the most useful for soil survey.

The techniques used on the reconnaissance soil surveys carried out in East Pakistan and Bangladesh between 1963 and 1975 were those described in the USDA Soil Survey Manual and the FAO Guidelines for soil description, adapted where necessary to suit local conditions.

From 1961 to 1970 a number of reconnaissance soil surveys were carried out by the Directorate of Soil Survey with the help of the Food and Agriculture Organisation (FAO). These soil surveys covered over eighty percent of the country. In these surveys the main soil unit recognised in the field was the soil series, which was defined to cover a range of soils derived from similar parent materials under similar conditions of development and resembling each other closely in their major physical and chemical properties. Important subdivisions of the soil series were recognised as soil phases. Instead of mapping individual soil units, which would result in very complicated patterns, the concept of soil association was developed. It was found that most areas had only a few types of soils occurring in a definite relationship with each other. The relationship is usually topographical, with soils of different types occurring at different levels. Though individual soil distribution forms a very complicated pattern, the regular relationship of some soils made it possible for them to be grouped together in soil association. In the Noakhali-Chandpur area 33 soil series were recognised and 41 soil associations were described. In addition to the classification of soils the reconnaissance survey classified land according to its capability for agricultural production and also suggested crop suitability. The soil resources development institute (SRDI), Bangladesh has published reconnaissance soil survey reports for all districts. [Md Sultan Hussain]