azolla unit

An Azolla production unit has been established in Krishi Vigyan Kendra, Medak to demonstrate its production technology to Farmers, Farm Women and Rural youth as paddy is the major crop in medak district and many of the tribal habitations (Thanda’s) depend on cattle rearing for their livelihood.

Azolla (Azolla pinnata) is an aquatic floating fern, found in temperate climate suitable for paddy cultivation. The fern appears as a green mat over water. The Blue Green Algae cyanobacteria (Anabaena azollae) present as a symbiont with this fern in the lower cavities actually fixes atmospheric nitrogen. The rate of nitrogen fixed is around 25 kg/ha.

For scientific and continuous production of Azolla requires cement concrete tanks of size 6 ft long, 4ft wide and 1ft deep as shallow depth is ideal for Azolla growth. Due care should be taken so that water can stand in the tank. Sieved fertile soil mixed with dung and water must be evenly plastered at bottom of tanks. The layout of the tanks is shown in the photograph (Pic-1). Fill the tank with water till the water collects to a height of 10 to 15 cm above the soil. Allow the soil particle to settle down. Remove the layer of foam and scum that forms on the surface of the water. The foam impedes the growth and root penetration of azolla. Allow the tank to stand overnight. On the following day, spread around 200 g of fresh Azolla inoculum over the surface of the water. It takes about 1-2 weeks for Azolla to form a mat over the water surface. Water level in the tank should be maintained especially during summer months. To reduce excessive ambient light, a shade made out of coconut leaves/Shade net may be laid above the tank. This also prevents dew formation on the growing Azolla during winter.

Initially, azolla will spread over the entire bed and will take the shape of thick mat within seven days. Ideally it will give 10 kg of azolla within seven days. During the initial seven days azolla is not harvested. Water level is maintained by applying water every day. After the seventh day, 1.5 kg of azolla can be harvested every day. Azolla should be harvested in plastic trays with sieve. The azolla wash can be used as bio-manure for plants grown nearby. Cow dung mixture removed by azolla mass has to be supplemented at least once in seven days after harvest. A mixture made of cow dung, soil and water should be added once in seven days. After every 60 days, soil is removed from the bed and another 15 kg of fresh fertile soil is added into the bed to avoid nitrogen build up and also provide nutrient to the azolla. Fresh inoculation of azolla after removing soil and water should be made at least once in six months repeating the whole process afresh.

As green manure, Azolla is grown alone for two to three weeks in flooded fields. Afterwards, water is drained out and Azolla fern is incorporated in the field before transplanting of paddy. Otherwise, 4-5 Kgs of fresh Azolla is applied in standing water one week after planting of paddy, after its even spreading water will be drained out from fields to allow azolla to decompose in respective paddy plots. Azolla is very rich in protein (25-35%), Calcium (67 mg/100g) and Iron (7.3 mg/100g). Harvested azolla should be washed in fresh water before it is fed to the cattle. Washing is necessary to remove the smell of cow dung. Azolla harvested can be mixed with the commercial feed in 1:1 ratio. Dry Azolla flakes can be used as poultry feed and green Azolla is also a good feed for fish. It can be used as a bio-fertilizer, a mosquito repellent, and above all as a bio-scavenger as it takes away all heavy metals.