Aquaculture Engineering

Detailed survey - Main factors - Soil Characteristics

Unit 2- Fish Farm

Detailed survey
Main factors - Soil characteristics
Soil characteristics play a vital role for selection of suitable site. The site should contain soft bottom soil or mixed soil comprising of clay, silt and sand in proper proportion to ensure good water holding capacity as well as production of natural food organisms on which aquatic organisms could feed and grow. One of the most important characteristics is the water holding capacity.

Gravel and sand are non-cohesive soils. Their cohesiveness almost nil under dry condition and have no plasticity. In sand and gravel bed water percolates easily. Hence sand and gravel bed are not suitable for pond construction. Clay, silt and fine grained soils are cohesive soils. Cohesive property imparts structural stability in pond dykes, bottom etc., clay is very absorbent under wet condition, it swells to double its volume. So only clay, silt are also not that much suitable for pond construction. A combination of cohesive and non-cohesive soils such as sand, silt and clay in proper proportion are suitable for pond construction. According to textural classification of soil, clay loam, sandy clay loam, silty clay loam and sandy clay soils are suitable for pond construction. Too much organic matter in the soil is harmful. Land with a layer of organic matter greater than 0.6 m deep is unsuitable for ponds. Because organic stratum will cause excessive seepage losses, when it decays. Highly organic soils are not suitable for dyke construction. Organic soils also cause rapid oxygen depletion in the pond water.