2. Algae
– They are unicellular, filamentous or colonial.
– They add biomass to the extend of 7 to 300 kg / ha .
– Soil algae are divided in to four main classes or phyla as follows:
1. Cyanophyta (Blue-green algae)
2. Chlorophyta (Grass-green algae)
3. Xanthophyta (Yellow-green algae)
4. Bacillariophyta (diatoms or golden-brown algae)
– blue-green algae and grass-green algae are more abundant in soil
– The green-grass algae and diatoms are dominant in the soils of temperate region while bluegreen algae
predominate in tropical soils.
– Green-algae prefer acid soils while blue green algae are commonly found in neutral and alkaline soils
3. Intro
– The most common genera of green algae found in soil are: Chlorella,
Chlamydomonas, Chlorococcum, Protosiphon etc. and that of diatoms are
Navicula, Pinnularia.
– The dominant genera of BGA in soil are: Chrococcus, Phormidium, Anabaena,
Aphanocapra, Oscillatoria etc.
– Some BGA posses specialized cells know as "Heterocyst" which is the sites of
nitrogen fixation.
– BGA fixes nitrogen (non-symbiotically) in puddle paddy/water logged paddy fields
(20-30 kg/ha/season
– Venkataraman (1961) coined the term 'algalization' to denote the process of
application of blue-green algal culture in field as biofertilizer.
4.
5. Mass production
The following four methods are used for mass cultivation :
(i) cemented tank method,
(ii) shallow metal troughs method,
(iii) polythene lined pit method, and
(iv) field method.
The polythene lined pit method is most suitable for small and marginal farmers to
prepared algal biofertilizer.
In this method, small pits are prepared in field and lined with thick polythene
sheets.
6. Steps
STEP 1 - Prepare the cemented tanks, shallow trays of iron
sheets or polythene lined pits in an open area. Width of tanks or
pits should not be more than 1.5 m. This will facilitate the
proper handling of culture.
STEP 2 - Transfer 2 -3 Kg soil (collected from open place for
lm 2 area of the tank) and add 100 g of superphosphate. Water
the pit to about 10 cm height. Mix lime to adjust the pH 7. Add
2 ml of insecticide e.g. malathion to protect the culture from
mosquitoes. Mix well and allow to settle down soil particles.
7.
8. STEP 3 - When water becomes clear, sprinkle 100 g of
starter inoculum on the surface of water.
STEP 4 - When temperature remains between 35-40°
during summer, optimum growth of cyanobacteria is
achieved. Always maintain the water level to about 10 cm
during this period
9. STEP 5 - After drying, the algal mat will get separated from the
soil and forms flakes. During summer about 1 kg pure algal mat
per m2 area is produced. These are collected, powdered, kept in
sealed polythene bags and supplied to the farmers.
STEP 6 - The algal flakes can be used as starter inoculum if the
same process is repeated.
