Page 35 - EER-2-2

Explora: Environment
and Resource Anabaena-Azolla for crops and bioenergy

growth of the microbial population is actively influenced waterlogged soil, releasing 60 – 80% of the nitrogen within
by degraded organic materials. Azolla application improves 2 weeks. In addition, it has been noted that the highest
mineralization, enhancing the microbiological status yield in wheat fields is achieved when Azolla is used at a
of the soil and promoting its biological health. Azolla rate of 20 tonnes. The application of Azolla in fields has
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produces considerable levels of micronutrients, in addition sufficiently increased the water holding capacity, organic
to nitrogen, including phosphorus, potassium, sulfur, nitrogen, carbon, nitrate-nitrogen, and other nutrients
zinc, iron, and molybdenum. The process of mineralizing such as phosphorous, calcium, potassium, and magnesium.
organic nitrogen to NH is essential to lowland rice In mung bean fields, the usage of Azolla has significantly
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farming, as it is influenced by the carbon-to-nitrogen ratio. increased yield. 30
Azolla species with a low carbon: nitrogen ratio mineralize
in 2 days, whereas those with a high carbon: nitrogen ratio 6.2. Cyanobacteria as biofertilizers for plant growth
take 5 days. Azolla is now grown alongside taro (Colocasia improvement
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esculenta), arrowhead (Sagittaria sagittifolia), and water There are reports of cyanobacterial inoculation having
bamboo (Zizanica aquatica). Initially, it was only utilized growth-promoting effects on a variety of crops, including
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as a green manure for rice. Azollae are easily harvested for rice, soybean (Glycine max L. Merr.), wheat (Triticum
use as fertilizer in sustainable agricultural practices and aestivum L.), radish (Raphanus sativus L.), oat (Avena
can be mass-cultivated using wastewater. 73 sativa L.), cotton (Gossypium hirsutum L.), lettuce (Lactuca
The work carried out by Seleiman et al. involved sativa L.), and tomato (Solanum lycopersicum L.). 69,77 In
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the application of Azolla, both individually and in soil, cyanobacteria create a network of their filaments that
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combination with other fertilizers, in Oryza sativa L. deeply enmesh soil particles. Moreover, cyanobacteria
Various combinations used in their experiment included: produce extracellular polysaccharides, which are
control (without fertilizer and compost), NPK-100%, hygroscopic and aid in binding soil particles together,
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NPK-70%, NPK-40%, Azolla compost-100%, NPK-50% thereby improving soil quality. In addition, it has been
and Azolla-50%, NPK-70% and Azolla compost-30%, and demonstrated that cyanobacteria produce a variety of
NPK-40% and Azolla compost-60%. The combination of substances that improve plant growth. In particular, they
NPK-70% + Azolla compost-30% and NPK-40% + Azolla influence plant height, root length, leaf count, dry root
compost-60% showed optimal growth with high yields. weight, fresh root weight, dry stem and leaf weight, and
Specifically, NPK-40% and Azolla compost-60% produced fresh stem and leaf weight in different vegetable plants.
a rice yield of 10.76 tonnes/ha, nearly equivalent to the Their effects have been observed in squash, cucumber,
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10.60 tonnes/ha obtained with 100% NPK. Overall, the and tomato. Cyanobacteria are known to associate
combination of NPK-50% and Azolla-50% produced the with both vascular and non-vascular plants, producing
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highest rice harvest at 11.13 tonnes/ha. 20 compounds that promote growth. When associated with
crop plants, cyanobacteria in the rhizosphere can enhance
Simarmata et al. analyzed the effects of Azolla extract the assimilation of organic molecules, which benefits crop
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on liquid biofertilizers for different rice varieties. They establishment, growth, and yield. By soaking rice seeds in
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divided the experiment into two main plots, T1 and T2 extracts from cyanobacterial cultures, researchers observed
(T1 – 3 tonnes/ha of compost and T2 – 3 tonnes/ha of increased grain weight and protein content, enhanced
compost plus 10 L/ha of Azolla extract), with five sub- shoot and root growth, and improved germination. These
plots for stress-tolerant varieties of rice (V1 – Inpari effects were attributed to hormones and vitamins, which
43, V2 – Mawar, V3 – Inpari 30, V4 – Inpara 03, and regulate plant growth. Cyanobacteria produce a vast range
V5 – Mendawak). The rice yield in T2 (Azolla extract- of substances, including amino acids, auxin, gibberellins,
treated field) showed a 37.06% higher yield compared abscisic acid, and cytokinins. These substances enhance
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to the control, with the average yield from the five nutrient availability and facilitate nutrient uptake by
varieties treated with Azolla extract (5.51 tonnes/ha) plants. Representative members of both symbiotic and
being greater than the local farmer’s yield (ranging from free-living species of cyanobacteria, such as Nostoc,
3.78 to 4.97 tonnes/ha). These findings suggest that the Anabaena, Calothrix, Chlorogloeopsis, Cylindrospermum,
application of Azolla extract as a biofertilizer in stress- Plectonema, Gloeothece, and Anabaenopsis, are capable
tolerant plants will significantly increase productivity in of producing indole acetic acid. 14,28 Anabaena can also
flood-prone coastal areas. 76 produce phytohormones such as auxins, gibberellin, and
Other than rice fields, Azolla is used in the cultivation cytokinins, which play a major role in promoting plant
of taro, arrowhead, wheat, water bamboo, etc. Azolla has growth. Phosphate, a mineral necessary for improving
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rapidly mineralized as a green manure when incubated in plant growth and development, is the limiting nutrient

Volume 2 Issue 2 (2025) 8 doi: 10.36922/eer.7975