Fertilizing fishponds with a combination of inorganic and organic fertilizers can improve the growth and quality of fish in the pond. Atty. Ceferino de Los Santos, Jr., a successful fishpond operator in Iloilo, recommends using both types of fertilizers to achieve the best results. Inorganic fertilizers, such as 18-46-0 and 16-20-0, can be used in conjunction with organic fertilizers, such as chicken, cow, or pig manure, and molasses, to create a balanced approach to fishpond fertilization.
Apply organic fertilizers first. Chicken, cow or pig manures are applied at the rate of 2,000 to 5,500 kilograms per hectare in new ponds or ponds with little organic mud.
Spread the manures after the pond bottom has been drained and dried. Dry and powdered manure should be spread evenly over the surface of the pond by putting them in sacks and letting manure drop out in ribbons as the spreader walks over the pond.
If wet, they are poured in heaps at equidistant spots over the pond and then spread out by shovels or spades.
Molasses as organic fertilizer was adopted by Atty. de Los Santos after seeing its effectiveness in Taiwan. It’s not only a fertilizer but a pesticide as well.
Apply it at the rate of 400 kg/ha. Dilute the molasses with pond water. Then pour it into the water gates as water is let into the pond. Maintain water depth at 5 to 10 cm for at least one week under a hot sun, or longer if sunlight intensity is not too great.
After two weeks, the pond may be stocked with fish. Water must be raised to the pond’s maximum holding capacity. Before stocking fish, make a preliminary test by putting in a few fish. This will determine if the oxygen level in the water is high enough for fish to live.
Organic fertilizers should be followed up with inorganic fertilizers like 18-46-0 or 16-20-0. The rate for 18-46-0 is 22 kilograms per hectare. Apply it on platforms when using plankton food.
For lablab food, apply it by broadcasting first, then by broadcasting again or by platforms. On the other hand, if you use 16-20-0, apply at 50 kilograms per hectare every 14 to 21 days or as needed.
You must however be sure that water visibility is maintained between 20 to 30 cm.
Fertilizing your Fishponds With Animal Manures
Organic manures such as those from chicken, cattle, carabaos and hogs are cheap sources of fertilizers for tilapia production. Some enterprising fishpond operators have put up poultry and piggery projects so that animal wastes are washed off directly to the pond.
Organic fertilizer should be applied particularly on newly constructed fishponds deficient in organic matter content. Here are some of its advantages:
1. Soil texture is improved.
2. Water holding capacity is increased
3. Soil is enriched.
4. There is a slow release of the major plant nutrients and other minerals.
5. Enhances the growth of lablab and zoo-plankton which are good natural sources of food for fish.
However, one must not spread decomposed organic fertilizer over the whole pond bottom. If you do that, oxygen in the water will be depleted. The required application should be placed in heaps of 20 to 30 kilograms.
Apply dried chicken manure at the rate of 500 to 1,000 kilograms per hectare. Other manures are applied at 1,000 to 2,000 kilograms per hectare.
The Value of Hog Manure as Fishpond Fertilizer
As a fertilizer, hog manure contains, by weight, 0.5 per cent nitrogen, 0.4 per cent phosphorous, and 0.3 per cent potassium. It has 25 per cent organic matter, about 0.09 per cent calcium and about 1 per cent of other elements. It of course contains 71 per cent water.
Experiences by an Iloilo integrated Bangus-piggery operator have shown that application of hog manure in ponds gives;
1 – a higher percentage turbidity reaction which means that the pond water becomes clearer after application
2 – steady increases in the abundance of lablab and other natural foods and,
3 – higher yields.
How to prepare hog manure as fertilizing medium:
(a) Mix about 1½ kilos of fresh manure with water in a big 8-gallon plastic pail. Leave the mixture overnight.
(b) Filter the mixture in a clean jute bag to remove the big particles.
(c) Use the filtrate – the water that has been filtered – and a small amount of urea added at a rate of 0.3 grams per litre of water as the fertilizing solution. Add this to the pond water.
Dried hog manure can also be applied at a rate of 13.5 sacks per hectare. It has been reported that manure from 20-30 pigs in a year can produce the same fertilizing effect as one ton of ammonium sulfate.
How Organic Fertilizers Improve Fishponds Yields
For newly built fishponds or those deficient in organic matter content, the application of organic fertilizer is highly recommended.
The most common organic fertilizer used in fishponds is chicken manure which normally contains 1.5 per cent nitrogen, 0.4 per cent phosphorous, and 0.37 per cent potassium, by volume.
Other sources of organic fertilizer are cattle dung (0.49%N; 0.07%P; 0.3%K), pig manure (0.49%N; 0.15%P; 0.5%K), composted rice straw and other plant materials.
Dried chicken manure is applied at the rate of 500 to 1,500 per hectare while other kinds of manure are used at the rate of 1,000 to 3,000 kilos per hectare.
Organic fertilizers give the following benefits:
1 – Improves the soil texture
2 – Increases the water-holding capacity of the soil
3 – Help conserve soil fertility and,
4 – Provides a steady source of major plant nutrients and other minerals.
In fishponds, organic manures help produce more fish food organisms like lablabs and zooplankton. Zooplanktons are very tiny animals that are free-floating in the water.