World Aquaculture 45 However, the actual dose has to be calculated based on pH of the soil and water (Table 2). Fertilization. Fertilization of the pond is an important means of intensifying fish culture by increasing natural productivity. A combination of both organic and inorganic fertilizers may be used for obtaining the best results. Fertilization should be suitably modified depending on fish growt, available food reserves, physico-chemical conditions and climatic conditions. • Organic. Manure is to be applied three days from after liming. Cow dung or any other manure of similar nutrient composition may be applied at 10,000 kg/ha. • Inorganic. Generally, inorganic fertilizers should be applied after 15 days of organic manuring. The requirement of nitrogenous and phosphate fertilizers varies with soil fertility (Table 3). In general, lime is applied at 300 kg/ha in one installment, preferably on the bottom soil when the pond is dry. Lime may also be applied on the water. After 15 days of accumulation of water if lime was added on the bottom soil or after 15 days of application of lime on the water, cow-dung may be applied at 10,000 kg/ha in one installment. After 20 days of application of cow dung, the pond should be stocked with fingerlings. Stocking. Fish fingerlings of 10 cm should be used for stocking at 5,000/ha. If fingerlings of smaller size are used, suitable allowance may be made accounting for some percentage of mortality. Depending on the availability of fingerlings and market conditions, stocking can be of three, four or six species in the combinations mentioned in Table 4. Post Stocking. Fish need much more food than what is available naturally in the pond. Fish should be fed with a mixture of rice bran and oilcake in equal quantities daily at four percent of body weight (Table 5). It is preferable to put feed on a bamboo tray that is then lowered to the pond bottom or it can be spread at the corners of the pond. Fish will get used to either type of feeding and aggregate at the same place at a particular time of the day when feed is provided. Manuring. Organic manuring may be done in monthly installments of 1,000 kg/ha. Inorganic fertilization may be done at monthly intervals alternating with organic manuring. However, the monthly rate of fertilization will depend on pond producFeeding bags are hanged in series. Table 3. Doses of inorganic fertilizer (kg/ha/month). Soil fertility status Ammonium sulphate Urea 1. Nitrogen (mg/100 g soil) i) High (51-75) 70 30 ii) Medium (26-50) 90 40 iii) Low (up to 25) 140 60 2. Phosphorus (mg/100 gm soil) Single super phosphate Triple super phosphate i) High (7-12) 40 15 ii) Medium (4-6) 50 20 iii) Low (up to 3) 70 30 Table 4. Species combinations (ratios) in composite fish culture. Species 3-species 4-species 6-species Catla 4.0 3.0 1.5 Rohu 3.0 3.0 2.0 Mrigal 3.0 2.0 1.5 Silver Carp - - 1.5 Grass Carp - - 1.5 Common Carp - 2.0 2.0 Deoiled rice bran bags stocked in the farm to feed fish. Table 5. Recommended feeding rate in composite fish culture per ha of pond. Culture period Quantity (kg/day) I quarter 1.5 to 3 II quarter 3 to 6 III quarter 6 to 9 IV quarter 9 to 12 Total (for one year) 1,655 to 2,700
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