Fertilization of Fish Ponds

The primary purpose of fertilization is to increase its productivity by increasing the essential nutrients Is to direct all the primary, secondary and tertiary levels of productivity towards the maximum yield of fish Ensure a more hygienic, economic and simpler means of increasing fish production compared to artificial feeding The use of organic manure known to Chinese as far back as 4 th and 5 th centuries, however, use of inorganic fertilizers has recently been developed

Inorganic fertilizers May be grouped as under: 1. Limestone & lime 2. Phosphorus 3. Nitrogen 4. Potassium 5. Magnesium 6. Trace elements 7. At present mostly DAP & Urea are used to provide most of the necessary elements in fish pond

Organic fertilizers Cow dung Poultry manure Compost fertilizer, sillage, sewage, oil cakes, etc. Considered more preferable due to: 1. Provide ready-made mass of organic matter containing all the necessary nutrients 2. Stimulate the growth of bacteria 3. Useful for conditioning the structure of soil 4. Release nutrients at slow rate thus sustaining fertility of water over a long period 5. Comparatively cheaper

Draw backs of organic fertilizers Cause oxygen deficit Introduce some harmful bacteria, parasites or diseases Favors diseases like gill rot Excessive use enhances the production toxic gases and Offend aesthetic value of a pond make pond less desirable for bathing, swimming and drinking

Dosages of fertilizers Per acre dose/15days during warm months Case 1: Di Ammonium Phosphate9kg Urea2kg Cow Dung500kg Case 2: Di Ammonium Phosphate4kg Urea3kg Poultry manure500kg

Use of domestic water or sewage Attracted wide attention in various parts of the world Not only reduce the cost but protects the environment An average production of kg/ha has been obtained in carp culture in China, Taiwan, Hongkong, and Israel In Poland, Wolny (1962) obtained a yield of 1318kg/ha by utilizing untreated sewage effluents Jhingran (1974), that fish ponds in Calcutta, when treated periodically with sewage diluted in 1:4 gave excellent results

Green manuring With the help of cut aquatic or terrestrial plants or by sowing a crop on the pond bottom also gives good results The cut plants in the form of raft-like bundles or stacked heaps are placed along the marginal areas of the bottom Soft plants should be preferred that decompose in days The decaying plants results in vigorous development of benthos, particularly oligo-chaetes and chironomid larvae which provide food to fish and enhance productivity

Compost fertilizer Widely used for fertilizing fish ponds in China and Taiwan Commonly prepared from organic manure and vegetable matter in especially constructed composting tanks or large earthen pits Methodology: 1. Pile, all available organic matter, such as green grass, leaves, aquatic weeds then cut into small pieces, rice husk, household garbage etc, about 30cm high 2. Put a layer of animal manure on top of this

1. Sprinkle lime and liquid manure or water may be added in the ratio of 100lit of every 100kg of plant matter, keep the pile moist but not wet 2. Repeat these layers of plant material, manure and lime until a 2-3 m high heap is formed 3. The top most layer is built up in the shape of dome and is covered with mud 4. Leave the compost exposed to air and sun for 4-6 weeks 5. Turn the pile with the help of shovel every few days 6. The compost becomes ready for use in about 3 months periods. It shrinks to about 1/10 of its original size 7. Topiador et al (1977) reported that in china is applied at the rate of kg/ha in three installments 8. Usually placed in the form of heaps in the corners of the pond

When to fertilize? when water temperature stabilizes above 60° F (usually February to April). Make the next two applications at two-week intervals. Make the fourth and subsequent applications when the water visibility exceeds 18 inches (usually every 3 to 5 weeks) Discontinue fertilization when the water becomes cold (below 60° F) in Oct./Nov. Repeat the above steps each year.

Ponds should be fertilized based on water visibility rather than a time interval. A 12 to 18 inch green visibility is ideal. A simple method for checking visibility is with a Secchi disk. Ponds that have been properly fertilized two or more years with a complete fertilizer may be fertilized adequately Using super-phosphate (18-20% phosphate) or 18 pounds of triple super -phosphate(46-52% phosphate) per acre per application