Soil quality is an important factor in fish pond productivity as it controls pond bottom stability, pH and salinity of overlying water and concentrations of plant nutrients required for the growth of phytoplankton, which is the base of food chain of the fish. A satisfactory site for constructing fish ponds is that where the soil is very deep, with low salinity levels and neutral pH, water infiltration is very low, mineralization of organic matter takes place rapidly, nutrients are adsorbed and released slowly over a long period. Moderately heavy textured soils because of their high surface area and surface charge density posses the above characteristics. Too heavier textured soils such as pure clay may not be satisfactory as they have very high adsorptive property and thereby act as a sink for nutrients like phosphorus which may not be easily released to the overlying water. These soils may also give problems of developments of deep cracks when dry (on draining the ponds) thereby allowing seepage losses of water.
In order to have a clear understanding of the various physicochemical and biological processes which are controlled by the soil in the ponds and to make decisions on the suitability of sites for aquaculture as well as effective managements of the soils for increased productivity of the ponds, one needs to have a good background knowledge of the nature and properties of the soil. This chapter presents basic information on soils, their characteristics and their applications to aquaculture. The physicochemical characteristics of water as they affect aquaculture. are discussed separately elsewhere. The science of aquaculture has many similarities with that of agriculture though it is of recent development compared to the latter. Many of the ideas in aquaculture are derived from the experiences in agriculture. Agriculture deals with soil-plant-animal relationships whereas aquaculture deals with the interaction of relationships of soil-water-phytobiota/zoobiota-fish (Fig. 1.1).
