An overview of underutilized benefits derived from Azolla as a promising biofertilizer in lowland rice production
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Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
cell press
Abstract
Currently, there is no doubt that Azolla can compensate for the nitrogen requirements of rice in
different agroecological zones. Compared to synthetic N-fertilizers, Azolla has various positive
impacts on lowland rice production, including improving soil fertility, minimizing weeds,
increasing soil organic carbon, improving microbial biomass, and thus nutrient cycling and
enhancing rice growth and yield. However, Azolla has not been accepted globally by rice farmers
for field use and so far, farmers are relying on increasing rates of synthetic N fertilizers instead of
taking advantage of Azolla which will improve long-term soil fertility and health. This systematic
literature review and scientific evidence could help policymakers, scientists and researchers to
understand the benefits, limitations, and innovative ways of utilizing Azolla as a cost-effective and
eco-friendly amendment in rice production. The paper uses Preferred Reporting Items for Sys tematic Review and Meta-Analysis (PRISMA) method to review the hidden potential of Azolla as a
biofertilizer in paddy and summarizes its benefits and problems by collecting information from
different sources and presenting under different subheadings such as critical factors affecting
Azolla growth and nitrogen fixation, nitrogen fixation of Anabaena Azollae and their contribution
in soil health, release and availability of Azolla-N to rice, amounts and time of Azolla inoculation,
influence of Azolla on ammonia volatilization, contribution of Azolla to yield and yield compo nents of rice, and impact of Azolla on weed emergence in rice cropping system. Literature indi cated that the use of Azolla as green manure incorporated before rice transplanting or grown
together with rice and left until a few days of harvest alone or in combinations with other syn thetic fertilizers in the lowland rice production saved the nitrogen requirement of rice up to 60 kg
N ha− 1
, it enhances the availability of nutrients, improves physiochemical properties of soils,
minimizes soil salinity, reduces the soil pH, and minimize weed germination. However, it was
observed that incorporating Azolla as green manure is labor-intensive, and maintaining the Azolla
inocula and phosphorous requirement are major restrictions for farmers. Therefore, under standing mechanism of spore production, educating farmers on cheaper alternative ways of Azolla
application, and testing different species of Azolla over different agroecological zones will help in
maintaining Azolla biomass and applying it at low cost for further environmental conservation.
Description
Journal Article
Keywords
Azolla, Soil health, Cyanobacteria, Cropping systems, Greenhouse gas emission