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Agriculture for Secondary Schools


                                                                Pond
                    Outside slide of dyke


                          Outlet


                                                Inside slide of dyke
                                                                                     Inlet

                                           Monk
                                                        Pond

                                Crest

                    Dyke




                                   Figure 12.4: Main parts of a fish pond
            Selection of site for earthen ponds
            The following things have to be considered in selecting site for earthen ponds:
            (a)  Reliable source of water
                 Water is the medium in which fish are cultured/grown. The source of water should
                 be available year-round and free from contaminants. Water is essential to fill the
                 ponds for stocking; to replace losses due to seepage or evaporation, for water
                 exchange, and to replace water in ponds during emergencies.

            (b)  Nature of soil
                 The pond soil must have enough clay content to ensure that the pond will hold
                 water. When clay soil absorbs water, it swells and seals the bottom and sides of
                 the pond. Pond banks of soil which is sandy will erode easily, and water will
                 leak out through the pond bottom.

            (c)  Topography
                 The land with gentle slope is considered ideal since it is able to allow water flow
                 by gravity. If possible, the land must be slightly lower than the water source so
                 that the ponds can be filled by gravity rather than by pumping. This reduces
                 energy inputs and operating costs. In addition, gentle slope eases construction
                 and drainage of pond.
            (d)  Vegetation of site
                 Areas with open wood land, grassland, old paddy fields and land covered with
                 low shrubs enable easy and cheap construction of pond. The site selected for
                 pond construction should not be heavily wooded in order to reduce the cost of
                 land clearing.

               Student’s Book Form Twos Book Form Three
             Student’
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