The coming decades will
be the challenge for agriculture to meet the world’s increasing demand for food
in a sustainable way. Due to declining soil fertility and mismanagement of
plant nutrients the task has become more difficult. Moreover, limited availability
of additional land for crop production along with declining yield for major
food crops have concerned the agriculturist to feed the world’s bursting
population which will exceed 12.5 billion by the year 2030. Therefore, future
strategies for increasing agricultural productivity have to be focused on using
available nutrient resources more effectively, judiciously and efficiently.
Here Integrated
Nutrient Management (INM) will play an important role in increasing
agricultural production and also safeguarding the environment for future
generation. INM is a strategy that incorporates both synthetic and biological
plant nutrient in a judicious manner for attaining higher crop productivity as
well as sustaining soil health for years to come.
Azolla Bio-fertilizer for flooded rice: One of the most important bio-fertilizers for wetland rice is the water fern Azolla and the blue green algae also known as floating nitrogen fertilizer factories. Both can grow alongside paddy. Azolla can also be used for green manuring, which could contribute from 20 to 60 kg per hectare N. Azolla is considered an efficient scavenger for potassium and serves as a source of K for rice crops.
Azolla Bio-fertilizer for flooded rice: One of the most important bio-fertilizers for wetland rice is the water fern Azolla and the blue green algae also known as floating nitrogen fertilizer factories. Both can grow alongside paddy. Azolla can also be used for green manuring, which could contribute from 20 to 60 kg per hectare N. Azolla is considered an efficient scavenger for potassium and serves as a source of K for rice crops.
Azolla:-
Azolla is a free floating water fern that floats in water. It is regarded as
the “Soybean plant in rice fields” because it can fix and assimilate nitrogen
owing to association for Cyanobacteria- Anabaena azollae in the dorsal
cavities of Azolla leaf (Moore, 1969). Azolla is found in ponds, ditches and
wetlands of warm-temperate and tropical regions throughout the world. The
Azolla plant is triangular or polygonal in shape and floats in water surface
individually or in mats. The plant has alternately arranged branches and
adventitious roots remaining hanging in standing water. Azolla multiples
vegetatively a sexually by producing spores. Vegetative reproduction is most
common and continues at all times. Presently, six species of Azolla have been
recognized worldwide. These are: Azolla filiculoides; A. caroliniana; A.
Mexicana; A. microphylla; A. pinnata and A. nilotica. Each individual
species has distinct geographic origin. For example- A. pinnata is
native to South East Asia, Oceania and Coastal Africa.
Importance of Azolla:
Cultivation of Azolla as biofertilizer input for rice has been recognized in
many Asian countries like China, Vietnam, Phillippines, Sri Lanka and
sporadically in India. Rice growing areas of these countries has been evincing
increased interest in the use of Azolla as an alternate N source or as a
supplement to commercial nitrogen fertilizers. Potentialities of Azolla as
alternate green manure can contribute 40-60 kg N/ha per rice crop with
significant increase in yield and productivity. Moreover, due its rapid decomposition nature, Azolla can add
considerable amount of organic matter in the soil subsequently releasing other
essential nutrients like K, Ca and Mg for better utilization by rice crop. Some
multiple benefits of Azolla are-
1. It acts as
biological herbicide depressing germination of weeds.
2. Accumulate nutrients
from flood water and release to rice crop after decomposition.
3. Due to its high
protein content (20-30% on dry weight basis) it can be used as organic feed
substitute for livestock.
4. Due to its rapid
decomposing nature, Azolla can be used as manure for dryland crops, vegetable
and ornamental plants.
5. On dry weight basis
Azolla contains Nitrogen (5%); Phosphorus (0.5%); Potassium (2-4.5%); Calcium
(0.1-1%); Magnesium (0.65%); Manganese (0.16%); Iron (0.26%); Crude fat
(3-3.3%) Sugar (3.4-3.5%); Ash (10%).
Methods of Azolla
cultivation
a). Homestead method:
Maintenance of fresh Azolla inoculums and off-season starter dose is very
essential prior to mass multiplication in the field. In this regard, a low cost
method for round the year maintenance of Azolla (A. caroliniana) under
homested condition has been developed by Assam Agricultural University. The
method involves preparation of pit size of 2 m length, 1 m wide and 20 cm depth
and covering with plastic gunnies followed by lining with 0.5 mm polythene
sheet. Rise the surrounding by mud plastering and pour water up to 10 cm. Mix
ingredients (SSP 10 gm + MOP 10 gm + 100 gm dry sieved cow dung) and apply to
each pit. Inoculate fresh Azolla @ 400 gm/pit and allow multiplying for
at least 15 days and harvest.
b). Field method:
Prepare and level the field uniformly. Divide the field into 20 m x 5 m
providing suitable bund and irrigation channel. Maintain water up to 10 cm gm
SSP in each plot. Harvest Azolla at 15-20 days after inoculation.
INM package for rice
with Azolla
By growing Azolla in separate plot:
1/10 of a hectare is needed to produce 20 tons/ha Azolla manure for
incorporation in the rice field.
Dual culturing of
Azolla with rice: This method is most feasible practice
under controlled irrigation system. In this method, fresh Azolla multiplied
elsewhere is applied @ 500 kg/ha as basal at 7-10 days after transplanting of
rice and allowed to grow for 15-20 days and thereafter incorporated. The
remaining Azolla again multiplies and grow to full bloom in another 15-20 days
which needs to be incorporated again.
Benefits:
- Basal application of Azolla manure @ 10 tons/ha increase soil nitrogen by 50-60 kg/ha and reduce 30-35 kg fertilizer nitrogen required by rice.
- Dual cropping with rice enrich soil nitrogen by 50 kg/ha and reduce N requirement by 20-30 kg/ha.
- Use of Azolla increase rice yield by 20 to 30%.
- The nitrogen obtained from Azolla is enough to support yield of 3 to 3.5 tons paddy/ha.