BIO-FERTILIZERS ARE eco friendly and are environmentally safe. They form not only part of integrated nutrients but are of low cost which is of immense help to the farming community. Biofertilizers are widely used in rice production. The biofertilizers used for rice crop are Azospirillum, Phosphobacteria, Blue green algae azolla and Mycorhiza.
Methods of application of biofertilizers and their usage are discussed below.
Azospirillum: is a symbiotic bacteria and it is an important biofertilizers used in rice. Azospirillum treatment is recommended for seed, seedlings and in main field.
Seed treatment: 600 glha of Azospirillum culture are to be mixed with water where the seeds are soaked one night before sowing in the nursery bed.
Seedling heatment: A slurry can be prepared by mixing Azospirillum at 1000 glha in 40 litres of water and root portion of transplanted rice seedlings are dipped in bacterial suspension for 15-30 minutes and then they are transplanted.
Main field: 2000 glha of Azospirillum with 25 kg farmyard mamure and 25 kg of soil are mixed uniformly and broadcasted in the main field before transplanting.
- Azospirillum bacteria thrives in root zones of rice and is capable of fixing more atmospheric nitrogen which is absorbed by the plants. Root exudates of the crops provide nutrients for survival and multiplication of the bacteria.
- Azospirillum also solubilizes phosphorus and silicon to some extent required by rice.
- It renders plant drought tolerant when irrigation or rainfall is delayed.
- By adopting Azospirillum application 30 per cent of the inorganic nitrogen usage can be reduced.
Blue Green Algae (BGA) is another type of biofertilizer used as an alga form. Important species are Cyanobacteria, Anabaena, Nostoc and Tolypothrix. Blue green algal occurs naturally and comes up well under moist conditions. This can also be artifially cultured.
Beds of size 20 x 2 m are prepared in a ploughed land bunded on all sides and water is let into the field to a height of 10 cm and maintained for 2-5 cm depth. 5 kg of Algal inoculum with 100g of lime are sprinkled for one cent plot.
Ater 30 days, without drainage of water, plot is dried and hence algal mat settles over the soil. Drying peel of like flakes is collected and distributed for rice field application at the rate of 10 Kg/ha, 10 days after transplanting.
Otherwise, algal flakes can be powdered, mixed with 25 kg of farmyard manure and 25 kg of soil and can be broadcasted. At the time of application, a thin film of water is to be maintained.
- The nitrogen fixed by BGA is about 15 kg/ha over a season.
- BGA elaborates vitamin Biz and growth factors that makes the plant grow vigorously.
- It oxygenates the water impounded in the field.
- It excretes organic acids that renders phosphorus solubilisation.
- The algal mat in paddy fields also protects loss of moisture from the soil.
Azolla is a water fern having an algal symbiont Anabaena azolla fixing atmospheric nitrogen.
Azolla can be multiplied by constructing nurseries with 10 cm deep standing water and adding superhphosphate at 8 kg P2o5/ha in small plots. Inoculation can be done at 8 kg/sq.m. Azolla can be used immediately after harvest.
It can be applied as green manure prior to rice planting or can be grown as dual crop with rice. About 10 tonnes of fresh Azolla per hectare is equivalent to 30 kgN/ha.
- Azolla excretes organic nitrogen in water during its growth and also immediately upon trampling.
-Fern fronds are soft and rapidly decomposed.
-It absorbs traces of potassium from irrigation water.
-Azolla provides nitrogen, potassium organic carbon etc.
-It prevents weed growth in rice field water.
Phosphobacteria: This type of biofertilizers solubilise phosphates in the soil and render them in available form for crop plants. It can be applied for low land and upland rice.
This is applied as the same dose in same manner as Azospirillum. Bacteria like Bacillus megatherium var phosphaticum, pseudomonas, fluorscens, fungi like Pencillium digitatum Aspergillus niger were found to have a strong phosphate dissolving ability.
Uses: 25 to 50 of the recommended Phosphorus can be reduced depending upon the native phosphorus content of the soil.
Mycorrhiza: It occurs naturally in low land and upland rice. It mobilizes the phosphorus required by rice. Mycorrhiza inoculation attempt in paddy nursery is still under study by Agricultural Universities of India.
Since, biofertilizers are ecofriendly inputs and are safer to the environment, farmers can adopt them and get benefited.
G.Lawrence Amal Raj
Arul Anandar College
Karumathur, 625 514