Trough method

Trough method:

Prepare shallow trays (2 m x 1 m x 23 cm) of galvanised iron sheet or permanent tank.
The size of the tank can be increased if more material is to be produced.
Spread 4-5 kg of river soil and mix well with 100 g of superphosphate and 2 g sodium molybdate.
Pour 5-15 cm of water in the trays. This will depend upon local conditions i.e. rate of evaporation. Mix the ingredients properly.
In order to avoid the nuisance of mosquitoes and insects add 10-15 g Furadon granules or malathion, or any other suitable granules.
The mixture of soil and water will settle within 8-10 hours.
At this time, add 200-250 g mother culture of blue green algae to the surface of water. Then don’t disturb water.
The reaction of the soil should be neutral. If the soil is acidic then add CaCO₃in order to bring the pH of the soil to neutral.
If sunlight and temperature are normal then within 10-15 days the growth of the blue green algae will look hard flakes on the surface of the water/soil. Similarly, water level will be reduced due to evaporation.
This way water in the tray/pit is allowed to evaporate and the growth of the algae flakes is allowed to dry.
If soil is dried the algal growth is separated from soil. These pieces of algal growth are collected and stored in plastic bags. In this way from one sq.m.tray or/pit about half tons kg blue green algal growth is obtained.
Again add water to trays and stir the soil well. Then allow the algae to grow in this way. This time it is not necessary to add mother culture of algae or superphosphate. In this manner one can harvest growth of algae 2-3 times. After this effect of superphosphate and soil is reduced.