Azolla Biofertilizer -The Nature's Miracle Gift for Sustainable Rice Production

Abstract

Azolla is a fast growing free floating freshwater fern which fixes atmospheric nitrogen by forming a symbiotic association with a prokaryotic cyanobacterium -Anabaena azollae. It is a costeffective, eco-friendly biofertilizer in lowland rice fields. As green manure in water logged soil, it enhances the rapid mineralization of nitrogen, improves the physical and chemical properties of the soil and increases soil microbial activities. It increases the rice yield equivalent to that produced by 30-60 kg N/ha. Azolla application is considered as a good practice for sustaining soil fertility and crop productivity.

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Azolla Biofertil-
izer – The Nature’s
Miracle Gift for
Sustainable Rice
Production
Kailash Chandra Samal*, Laxmipreeya
Behera and Jyoti Prakash Sahoo
Dept. of Agricultural Biotechnology, College of Agriculture,
Odisha University of Agriculture and Technology, Bhubaneswar,
Odisha (751 003), India
Kailash Chandra Samal
e-mail: samalkcouat@gmail.com
Azolla, Bioferlizer, Nitrogen xaon, Rice culvaon
How to cite this article?
Samal et al., 2020. Azolla Biofertilizer – e Nature’s
Miracle Gift for Sustainable Rice Production. Biotica
Research Today 2(9): 971-973.
Corresponding Author
Keywords
Open Access
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Abstract
Arcle: RT0350
Introducon
Azolla is a oang aquac fern and belongs to Phylum-
Pteridophyta; Class-Filicopsida; Order-Salviniales;
Family-Azollaceae. It has branched, short, floating
stem and bearing roots which oat over water. Azolla has a
characterisc bilobed leaf that consists of a dorsal and ventral
lobe. The dorsal lobe is green or purple in colour and has a
central cavity which houses the symbioc blue-green alga
Anabaena azollae. The ventral lobe is relavely thin and always
remains parally submerged in water and provides buoyancy
(Raja et al., 2012). The worldwide distribuon of Azolla is
represented by following six recognizable species: Azolla
pinnata, A. liculoides, A. rubra, A. microphylla, A. imbricate
and A. caroliniana and all these contain the Anabaena azollae
associaon (Raja et al., 2012).
Azolla forms a symbioc associaon with the prokaryoc
blue-green alga Anabaena azollae (Figure 1). In this associaon,
the eukaryoc partner Azolla provides shelterto the cyano-
bacterium Anabaena azollae in its leaf cavies and also supplies
carbon source. In return Anabaena azollae xes atmospheric
nitrogen and provides ammonia to the Azolla (Ana, 2018).
The Anabaena azollae is a prokaryoc cell containing three
types of cells- vegetative cells, heterocysts and akinetes
(Figure 1). The vegetave cells are highly pigmented whereas
heterocysts are large, thick walled, lightly pigmented cells and
the average heterocyst frequency is 7 to 20 %. The akinetes
are not usually seen and these are the resng spores which
are formed from the vegetave cells during unfavourable
harsh climatic condition. Nitrogen fixation occurs inside
the heterocyst which provides an anaerobic environment
and in which the atmospheric nitrogen (N2) is reduced to
ammonia (NH3) in the presence of the enzyme nitrogenase.
The requirement of ATP and reductant (NADPH+) for this
reacon is obtained from the photosynthec acvity of the
vegetave cells. An average of 35-50 % ammonia xed by the
cyanobacterium is released to the eld and for this reason it
is used as a bioferlizer in the rice elds (Ana, 2018).
Biotica
Research
Today
Azolla is a fast growing free oang freshwater fern which xes
atmospheric nitrogen by forming a symbioc associaon with
a prokaryoc cyanobacterium -Anabaena azollae. It is a cost-
eecve, eco-friendly bioferlizer in lowland rice elds. As green
manure in water logged soil, it enhances the rapid mineralizaon
of nitrogen, improves the physical and chemical properes of the
soil and increases soil microbial acvies. It increases the rice yield
equivalent to that produced by 30-60 kg N/ha. Azolla applicaon is
considered as a good pracce for sustaining soil ferlity and crop
producvity.
2020
Popular Article
(Success Story
Vol 2:9
971
973
Article History
Received in 28th September 2020
Received in revised form 28th September 2020
Accepted in nal form 29th September 2020
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© 2020
Samal et al., 2020
Azolla as Bioferlizer
Azolla bioferlizer is the most suitable for the lowland
rice as both rice crop and fern require similar
environmental condions. Due to its rapid growth, high
nitrogen xing capacity, quick decomposion, Azolla is an eco-
friendly and cost-eecve bioferlizer. It is used as bioferlizer
extensively in rice. It not only increases the ferlity status
of the soil but also improves soil health. It also suppresses
weeds and reduces volalizaon of ammonia in rice elds
and substanally increases the amount of nitrogen ferlizer
available to growing rice. It can able to reduce the cost of rice
culvaon, improve soil health and boost yields sustainably
(Muhammad et al., 2020). It has huge potenal to increase
global rice producon and hence provides food security.
It can be ulized by rice in both wet and dry season. Azolla
can be used in two ways: as green manure incorporated
before transplanng, and as an intercrop incorporated aer
transplanng. In each case, about 500 kg (fresh weight) per ha
is introduced into standing water in the rice eld. About 5% of
the nitrogen sequestered by Azolla is available immediately
to the growing rice plants. The remaining 95% remains in the
biomass of Azolla and as the Azolla decomposes, its organic
nitrogen is rapidly mineralized and released as ammonia (30-
60 kg N/ha), which then becomes available to the growing
rice plants. The eecveness of Azolla as a bioferlizer on
rice depends upon various climac condions, methods of
applicaon and use of Azolla species etc. Azolla is used in rice
culvaon in two ways: Pre-transplanng incorporaon and
Intercropped Azolla. Increase in grain yields of rice from 14%
to 40% has been reported with Azolla being used as a dual
crop. The use of Azolla as monocarp during the fallow season
has shown to increase rice yield by 15-20 %.
Low Cost Technique of Azolla
Mulplicaon in Nursery Bed
As Azolla mulplies vegetavely, so Azolla (inoculum) is
maintained throughout the year by growing in small
ponds or water lled open eld. Azolla grows best
at a 25 °C average daily temperature but dies at a higher
temperature. For the producon of the inial inoculum, a
suitable semi-shade place is selected. Two feet depth pit
is dug and a UV stabilized polythene sheet of 2 m × 2 m
size is uniformly spread pit. About 10-15 kg of sieved soil is
uniformly spread over the pit. Cow dung slurry is prepared
by mixing 2 kg cow dung and 30 g of superphosphate mixed
in 10 litres of water. The slurry is poured in the pit and then
freshwater is added to raise the water level to about 10 cm.
About 0.5-1 kg of pure mother Azolla culture seed material is
spread uniformly over the water. The Azolla grows in the pit.
Aer a week a mixture of 20 g of superphosphate and about
1 kg of cow dung should be added once in 5 days to maintain
rapid mulplicaon of the Azolla. The Furadon granules (10
g) can also be added at fortnight intervals. Azolla will grow
rapidly and ll the pit within 10-15 days. From then on, 500
- 600 g of Azolla can be harvested daily and used for further
mulplicaon.
Azolla Bioferlizer Applicaon
It can be ulized by rice in both wet and dry season. Azolla
can be used in two ways: 1) as green manure incorporated
before transplanng, and 2) as an intercrop incorporated
aer transplanng. In each case, about 500-1000 kg (fresh
weight) per ha is introduced into standing water in the rice
eld.
As Green Manure Incorporated Before Transplanng
The elds are ooded to a shallow depth, about 3-4 cm,
and ‘seeded’ with Azolla at a rate of 500-1000 kg/ha.
Ferlizer applicaon of 2.2 kg Phosphorus (P)/ha every
5 days, 4 kg K/ha every 10 days, and 500−1000 kg/ha farmyard
manure every 5−10 days is carried during the growth of Azolla
in the eld. When the eld is covered with a mat of Azolla
(about 20 ton/ha) and which usually takes about three weeks
or more, the water is drained o and the Azolla ploughed into
the soil. The incorporaon of Azolla in the eld supplies 30 to
60 kg N/ha. Rice is transplanted 2-3 days later.
As An Intercrop Incorporated Aer Transplanng
The other technique Azolla is applied in the paddy eld
after one week of transplanting. Azolla is of great
agronomic value for rice crop where it is used as a dual
crop with rice and contributes 40-60 kg N/haper rice crop.
Benets
Azolla provides a variety of benets for rice producon and
grows in a way that is complementary to rice culvaon:
• The thick Azolla mat in rice elds suppresses weeds and
reduces ammonia volalizaon.
• It xes atmospheric nitrogen provides to the plant during
its growth.
• Aer full vegetave growth of rice, Azolla begins to die and
decompose due to low light intensies under the canopy
and its nitrogen, phosphorus and other nutrients are rapidly
Figure 1: Azolla and its symbioc Anabaena azollae
a) Azolla-a feee floatinga-
quac fern
b) Microscopic view of anabaena
azollae
(Source- hps://img.brainkart.com/extra3/7f3QMvI.jpg)
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© 2020
released into the water and made available for uptake by rice
during grain development.
• In contrast with chemical nitrogenous ferlizers, Azolla has
various posive long-term eects, including the improvement
of soil ferlity by increasing total nitrogen, organic carbon, plus
phosphorus, potassium, other nutrients and organic maer.
• It enhances microbial populaon in the soil and improves
the physical and chemical properes of the soil.
• Azolla contributes 40-60 kg N/ha per rice crop.
Conclusion
The connuous usages of chemical ferlizers have harmful
eects on soil organic maer reserves, soil health and
environmental safety and so there is an increasing
concern about sustaining soil ferlity and environmental
health. The use of bio-ferlizers like Azolla increases rice
producvity and also improves the long term soil ferlity.
Applicaon of bioferlizer like Azolla could help eecvely
developing countries to improve more sustainable agriculture,
without the risk of problems associated with the adverse
eects of chemical ferlizers on long term soil ferlity, soil
producvity and environmental issues. It also improves the
physical and chemical properes of the soil and enhances
microbial populaon in the soil thereby maintains soil health.
References
Ana, L.P., 2018. The Unique Symbioc System between a
Fern and a Cyanobacterium, Azolla-Anabaena azollae:
Their Potenal as Bioferlizer, Feed, and Remediaon.
In Everlon Cid Rigobelo Ed. Symbiosis. DOI: 10.5772/
intechopen.70466.
Muhammad, A., Nadeem, S., Arooba, A., Amjad, E., Shafaqat,
A., Muhammad, R., 2020. Beneficial role of Azolla
sp. in paddy soils and their use as bioremediators in
polluted aqueous environments: implicaons and future
perspecves, Archives of Agronomy and Soil Science,
DOI: 10.1080/03650340.2020.1786885.
Raja, W., Rathaur, P., John, S.A., Ramteke, P.W., 2012. Azolla-
Anabaena associaon and its signicance in supportable
agriculture. Journal Biology and Chemistry, 40(1), 1–6.
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