Chapter 10.10
10.10 - Azolla as a Sustainable Animal Feed for Smallholder Farmers
Julia Oliverio,University of Guelph, Canada
Suggested citation for this chapter.
Oliverio,J. (2022) Azolla as a Sustainable Animal Feed for Smallholder Farmers, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Introduction to Azolla
Low protein content in livestock feed is a problem for many farmers; a potential solution to this problem is Azolla. Azolla, commonly known as duckweed or mosquito fern, is an aquatic plant that floats freely on the surface of water and belongs to the Salviniaceae family (Anitha et al. 2016). Azolla has a symbiotic relationship with the bacterium Anabaena which converts abundant atmospheric nitrogen gas into ammonia; ammonia then acts as a building block for amino acids and hence protein (Thomas et al. 1978). Due to this symbiosis, Azolla can grow with little nitrogen fertilizer, but results in a high protein feed (Thomas et al. 1978). There are six known species of Azolla, including A. pinnata which is most popular in Asia, and A. filiculoides which is most popular in the Americas; these are the two the oldest known species of Azolla (Lumpkin and Plucknett 1980; FAO 1977). Azolla grows naturally in bodies of freshwater in tropical, subtropical, and warm-temperate climate zones (Wagner 1997). Azolla floats on the water surface with horizontal fronds; the size of fronds varies greatly by species and can range from 1-15 cm (FAO 1977). The colour also varies by species from green to purplish red (FAO 1977). The promotion of Azolla as an animal feed is relatively new compared to its main use as a biofertilizer (Chander 2011). Azolla is often negatively perceived by some farmers because it is often considered to be a noxious weed, which contributes to its under-use (Lumpkin and Plucknett 1980). The following analysis is meant to shed light on the benefits and challenges of Azolla cultivation and its use as animal feed for smallholder farmers.
Nutrient Profile
The energy, protein and fibre levels of Azolla are comparable to that of lucerne hay, wheat grain, and canola meal, which are other commonly used cattle feeds (Huggins 2007). A. filiculoides contains a high protein content of between 20.3-31.2% and 9.2-11.3% of crude fibre (Shiomi and Kitoh 2001). For A. pinnata, the crude protein content is approximately 22.48% and the crude fibre is 14.70% (Anitha et al. 2016). Based on protein content, A. filiculoides is considered more suitable than A. pinnata for use as an animal feed (Brouwer et al. 2018). Azolla contains a higher proportion of essential amino acids than the common animal feed soybean meal, excluding histidine yet this is not a limiting factor (Brouwer et al. 2018). Azolla does suffer from phosphorus, calcium and sometimes potassium deficiencies which can restrict its growth; phosphorus fertilizer should be added at 2.5 kg per hectare (FAO 1977). Other components affecting digestibility of Azolla must be characterized then bred or extracted out to be domesticated as an optimal protein crop (Brouwer et al. 2018). Yet its protein content and promising amino acid profile make Azolla a good contender for a livestock feed.
How to Grow Azolla
There are several cost-effective methods for Azolla cultivation, as described by India’s Natural Resources Development Project (NARDEP) (Biswas and Sarkar 2013). First, an area of 2 m x 2 m should be levelled, surrounded with bricks, and covered with a plastic tarp. This area should ideally be exposed to 50% sunlight; the pits should be shaded by a tree or canopy if possible. Next, 10-15 kg of soil should be spread within the pit, followed by a slurry of 2 kg cow dung, 30 g super phosphate, and 10 litres of water; water should be added as needed to reach a depth of 10 cm, ensuring the Azolla can float. The pH of the Azolla pit should stay within 4-7.5 range. Then 0.5-1 kg of Azolla culture should be added uniformly over the water, stirred mildly, then more water should be sprinkled immediately after inoculation to ensure the Azolla grows upright. Every 5 days a mixture of 20 g superphosphate and 1 kg of cow dung should be added to ensure 500 g of Azolla can be harvested daily. To enhance mineral content, a micronutrient mix can be added on a weekly basis. 5 kg of soil should be replaced with fresh soil every 30 days, and 25-30% of the water every 10 days. The Azolla bed should be refreshed with new water, soil, and Azolla once every six months or if it becomes contaminated by pests and diseases. After the initial 10-15 days, around 500 g of Azolla should be harvested daily with a plastic sieve and washed thoroughly to remove the smell of cow dung before feeding to animals (Biswas and Sarkar 2013).
Benefits to Azolla
Azolla’s ability to be cultivated easily, along with its high productivity and good nutritive value, give it the potential to be a beneficial fodder supplement (Anitha et al. 2016). The above production system uses a continuous harvesting method that allows for high daily yields without the use of commercial nitrogen fertilizer; in addition, its favourable amino acid profile suits the application of Azolla as animal feed (Brouwer et al. 2018). Growing Azolla can reduce costs by roughly 20-25% compared to purchasing commercial animal feeds; Azolla typically costs farmers 0.60-0.65 Indian Rupees (US$0.015) per kg according to trials conducted by the Indian agricultural training centre, Krishi Vigyan Kendra in 2008-2009 (Chander 2011).
Azolla also has benefits beyond its potential as a livestock feed. The Azolla-Anabaena symbiosis generates a source of organic nitrogen fertilizer and is even considered to be aquatic green manure (FAO 1997). As a result, Azolla-Anabaena can produce 1 ton of green manure per hectare per day, containing 3 kg of fixed nitrogen (FAO 1977). Due to its high nitrogen fixation and growth rates, Azolla has traditionally been used in rice paddies as a bio-fertilizer for centuries; this has also helped to reduce greenhouse gas emissions compared to rice cultivation that relies on synthetic nitrogen fertilizer, produced using natural gas (Brouwer et al. 2018). Additionally, Azolla has been used to help purify water, as an ingredient in soup, to cure sore throats, and as a food source for humans (Lumpkin and Plucknett 1980). Azolla cultivation also presents an opportunity for female farmers as a source of income, reportedly sold at a rate of Rs. 10 per kg (Subbiah 2017).
Challenges to Azolla
The main challenges of Azolla cultivation include its inability to grow and withstand hot and cold temperatures, pest and disease control, and its singular method of vegetative propagation through water (FAO 1977). Viable stocks of Azolla need to be kept year-round which presents problems during very hot and very cold months (FAO 1977). Elevated or low temperatures, particularly in cold regions and dry zones where the temperature exceeds 40˚C can adversely affect Azolla growth (Chander 2011). Pests and diseases are a profoundly severe problem for Azolla, particularly during summer months or in hot temperatures (FAO 1977). The main pests are larvae of lepidopterous and dipterous species which eat the leaves of Azolla; rymanae fungus is also problematic (FAO 1977). Pests can be controlled with 2.5-3 kg of Furadan pesticide per hectare; if care is not taken, pests can destroy the crop within 3-5 days, Azolla pits would then need to be rebuilt which is costly and requires labour (Lumpkin and Plucknett 1980). Additionally, the availability of water highly restricts where Azolla can and cannot be cultivated, and furthermore water must be regularly changed to maintain healthy yields; both of these issues are problematic in places that experience dry seasons (Chander 2011). This also contributes to the difficulty of storing Azolla which remains a challenge (Shiomi and Kitoh 2001). Research is being conducted towards the propagation of Azolla through spores, which if successful will make it more accessible to smallholder farmers living in areas of climate volatility (FAO 2011). Azolla’s high moisture content and short shelf-life, makes it incredibly difficult to store or transport to market (Chander 2011). Due to storage challenges attributed to Azolla's low percentage of dry matter content (roughly 6%), farmers must commit to year-round crop maintenance (Huggins 2007). This also contributes to a lack of access to Azolla-Anabaena if not cultivated nearby. This presents an opportunity within Africa for an organization dedicated to providing access to Azolla-Anabaena culture and additional informational resources to smallholder farmers interested in growing Azolla.
Cost-Benefit Analysis
The cultivation of Azolla has the potential to increase yields, minimize costs, and enhance the economic status of smallholder farmers (Wagner 1997). As discussed above, its ability to produce high daily yields, generate sufficient protein and a balanced amino acid profile, and its ability to be produced at a low cost are all reasons to advocate for the use of Azolla as an alternative animal feed. However, there are practical concerns that need to be addressed. Depending on the animals being fed, the amount of Azolla needed varies. Per day, cattle require 1.5-2 kg, goats require 200-500 g, pigs require 1.5-2.0 kg, while layers and broilers (poultry) require 20-30 g (Chander 2011). The sample pit described by NARDEP produces roughly 500 g of Azolla per day, meaning larger or multiple pits may be necessary, possibly requiring additional labour through cooperatives. Azolla's specific environmental requirements and its problems with pests and storage are all other concerns that must be considered by farmers before adopting Azolla cultivation. Farmer cooperatives could be beneficial for the cultivation of Azolla to foster widespread knowledge, ensuring the meticulous techniques of fertilization and protection from insects are properly performed (Lumpkin and Plucknett 1980). Breeding and selection for more favourable Azolla strains could prove useful for farmers situated in unfavourable climate zones for Azolla cultivation (Brouwer et al. 2018). Ultimately, the adoption of Azolla as a sustainable cost-effective animal feed alternative remains dependent on smallholder farmer preferences and physical environments.
Additional Information Links
https://www.accessagriculture.org/growing-azolla-feed Video explaining how to make azolla pits
https://www.youtube.com/watch?v=HqbVca1elak&ab_channel=SpaceforNature Video explaining Azolla cultivation
https://www.youtube.com/watch?v=AY-JzEMpvKU&ab_channel=SpaceforNature Video explaining how to feed Azolla to animals
https://www.feedipedia.org/node/565 General and nutritional information about Azolla
https://www.agrifarming.in/azolla-farming-project-report Blog about Azolla farming in India
http://theazollafoundation.org/azollas-uses/as-a-livestock-feed/ General information on Azolla for animal feed
http://theazollafoundation.org/growing-azolla/cultivation-of-azolla-as-a-livestock-feed/ Website explaining Azolla cultivation
References
1. Anitha, K. C., Rajeshwari, Y. B., Prasanna, S. B., & Shree, S. J. (2016). Nutritive Evaluation of Azolla as Livestock Feed. Journal of Experimental Biology and Agricultural Sciences., 4(6), 670–674.
2.Biswas, S., Sarkar, S. (2013). Azolla cultivation: A supplementary cattle feed production through natural resource management. Agriculture Update. Hind Agricultural Research and Training Institute. 8(4), 670-672.
3.Brouwer, P., Schluepmann, H., Nierop, K. G. J., Elderson, J., Bijl, P. K., van der Meer, I., de Visser, W., Reichart, G.-J., Smeekens, S., & van der Werf, A. (2018). Growing Azolla to produce sustainable protein feed: the effect of differing species and CO2 concentrations on biomass productivity and chemical composition. Journal of the Science of Food and Agriculture, 98(12), 4759–4768.
4.Chander, M. (2011). Azolla: A sustainable animal feed? In Successes and failures with animal nutrition practices and technologies in developing countries (pp. 119–123). Food and Agricultural Organization of the United Nations (FAO), Rome. Retrieved from https://www.fao.org/3/i2270e/i2270e.pdf
5.FAO. (1977). China: Azolla Propagation and Small-scale Biogas Technology. Food and Agricultural Organization of the United Nations, Rome. Retrieved from https://www.fao.org/3/ar120e/ ar120e.pdf
6.Huggins, D. (2007). Evaluation of Azolla plant as an alternative stockfeed source. Prepared For: Goulburn Broken Catchment Authority. Retrieved from https://www.gbcma.vic.gov.au/downloads/EnvironmentalFlows/2007-12-13_Evaluation_of_Azolla_Plant_as_an_Alternative_Stockfeed_Source.pdf
7. Lumpkin, T.A., Plucknett, D.L. (1980). Azolla: Botany, physiology, and use as a green manure. Economic Botany 34, 111–153. https://doi.org/10.1007/BF02858627
8. Shiomi, N., Kitoh, S. (2001). Culture of Azolla in a pond, nutrient composition, and use as fish feed. Soil Science and Plant Nutrition., 47(1), 27–34.
9. Subbiah, G. (2017). Azolla cultivation in generating income for farm women. Approaches in Poultry, Dairy & Veterinary Sciences, 1(5).
https://doi.org/10.31031/apdv.2017.01.00052110. Thomas B. R., Peters, G. A., Toia, R. E., & Mayne, B. C. (1978). Azolla-Anabaena Relationship. VII. Distribution of Ammonia-Assimilating Enzymes, Protein, and Chlorophyll between Host and Symbiont. Plant Physiology, 62(3), 463–467. http://www.jstor.org/stable/4265459
12. Wagner, G. (1997). Azolla: A Review of Its Biology and Utilization. The Botanical Review, 63(1), 1–26.