3. SOIL PROPERTIES IMPORTANT FOR FRESHWATER FISH CULTURE
3.0 Classification tests
To define the different kinds of soils, you will have to perform various classification tests.
If you are planning to build a small fish-farm, most of the classification tests required can be done by you in the field.
If you are planning to build a large fish-farm, more complex classification tests may be necessary and you will have to request them from a specialized laboratory. You should know which tests to ask for and you should be able to understand their results. For a more precise interpretation, you may have to consult a civil engineer and you must be able to interpret his technical conclusions. You will learn how later in this manual.
Classification tests help decide the particular soil properties (or index properties) which will form the basis for defining the kinds of soils present at the selected construction site. Once the kinds of soils have been defined, it will be possible to determine their value as pond bottom or construction material for dams and dikes. The data given to you in Chapter 12 will help you.
3.1 Index properties of soils for freshwater fish culture
Planning a large fish-farm
If your construction project is large in size, you will need more detailed soil studies. The index properties required for an adequate description of the various types of soils for freshwater fish culture engineering are listed in Table 3. These properties will give you a fair idea of the physical properties of your soil on which to base the design of your fish-farm. If you plan to build a large fish-farm, begin by doing the following:
- Determine your basic types of soils (see Section 17);
- Using Table 3, make a list of the classification tests necessary to find the index properties for these soil types;
- Do whatever tests you can yourself, preferably in the field;
- Take your soil samples to a soil testing laboratory to perform the other necessary tests;
- Once you have the results, compare them with the data given in Chapter 11 and classify your soils;
- According to Chapter 12, define the main physical characteristics of your soils as pond bottoms and as construction material for dams and dikes.
Except for some vertical permeability measurements, these determinations should be made for each individual horizon separately. The following sections will help you to perform these simple field tests yourself. More technical methods will also be given for those with the necessary background to understand and apply them.
Note:you have seen in Section 2.1 that there are two kinds of samples, disturbed and undisturbed, and you have seen in Section 2.2 how to take them in the field. When you have decided which index properties of soils are essential in your case, you must be sure to obtain the kind of soil samples that you need. They are:
- Undisturbed samples for structure and permeability;
- Disturbed samples for all the other index properties.
Planning a small fish-farm
If your construction project is small in size, field tests may be sufficient to qualify the following soil properties:
- Colour, a good indication of drainage conditions;
- Texture, the relative proportions of particles of various sizes;
- Structure, the way in which the soil particles are assembled;
- Consistency and plasticity, the strength with which the soil material is held together when dry, moist or wet;
- Permeability, the rate at which water seeps down vertically.
|
(L) = Laboratory test |
