WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2024 57 (CONTINUED ON PAGE 58) 5) Add 20 gm Single Superphosphate and leave for one day 6) Stock 100 gm Azolla 7) Allow to multiply for 15 days 8) Harvest and repeat the above procedures Azolla Culture Conditions Azolla prefers sunlight under partial shade conditions for photosynthesis, with at least 13 cm of water for proper growth. Azolla grows well where the ideal temperature range is 20-35° C. It requires water pH of 5 to 7.2 and relative humidity of 80-90 percent (Table 1). Places with partial but adequate sunlight should be preferred. Nutrients, especially micronutrients, should be supplemented as required. Azolla Culture Techniques Azolla may be grown in (i) pits, (ii) containers, or (iii) ponds, however, the area and the size of an Azolla culture unit depends on the quantity to be harvested and the availability of space. Because culture can be done with low investment under resource-poor conditions, small, marginal, landless and resource-poor farmers can adopt the culture technology. These are the steps for culture of Azolla in pits and containers: 1) Prepare a pit of required dimension 2 m length, 1 m width and 20 cm depth or use a 500 L shallow fiber-reinforced plastic (FRP) tank in either circular or rectangular shape (Figure 2) 2) Spread plastic sheets over pit 3) Mix 8 kg soil and 1.5 kg old cow dung and spread in the pit or FRP tank 4) Fill with dechlorinated tap water and leave for three days TABLE 1. Environmental requirement for Azolla. S. N. Parameters Desirable value 1 Water level 10-15 cm 2 Light Partial shade 3 Temperature 20-35 °C 4 Relative humidity 80-90% 5 pH 5.0-7.2 6 Phosphorous 20 kg/ha TABLE 2. Chemical composition of Azolla. SN Nutrients % Contents SN Nutrients % Contents (dry weight basis) (dry weight basis) 1 Crude Protein 20-30 9 Magnesium 0.25-0.65 2 Amino acids 7-10 10 Sodium 0.49-1.24 3 Nitrogen free extract 30.0-47.0 11 Potassium 2.19 - 4.93 4 Ether extract 2.37-6.70 12 Manganese (ppm) 83.9-2418 5 Total ash 15.7-19.9 13 Iron (ppm) 283-1569 6 Crude fiber 12.6-17.5 14 Copper (ppm) 9.10-26.2 7 Calcium 0.80-2.22 15 Carotene (ppm) 206-632 8 Phosphorous 0.35-1.29 Source: Swain et al., 2022 TABLE 3. Recommendation of Azolla as aquafeed ingredient in fish diet. SN Cultured fish Azolla (%) SN Cultured fish Azolla (%) 1 Catla (Catla catla) 20-50 7 GIFT tilapia 10-20 2 Rohu (Labeo rohita) 50 8 Mozambique tilapia (Oreochromis mossambicus) 20 3 Mrigal (Cirrhinus mrigala) 10-25 9 Nile tilapia (Oreochromis niloticus) 20-25 4 Fringed-lipped carp 40 (Labeo fimbriatus) 10 Thai Silver barb (Barbonymus gonionotus) 25 5 Calbasu (Labeo calbasu) 30 11 Grass carp (Ctenopharyngodon idella) 30 6 Common carp (Cyprinus carpio) 40 12 Pangasius catfish (Pangasianodon hypophthalmus) 10
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