Look to the Weeds in Saving the World before Breakfast


For thousands of years, farmers have wailed on weeds with hoes and plucked bugs off their plants.  They have fought back much more powerfully in the 1900s and 2000s with power weeders, pesticides, and herbicides.

But, the pests and weeds need not be problems.  Sometimes, they can be part of the solution in developing a more efficient food-producing system.  That better food production is something humanity will need to feed a bigger population coming and for doing that despite serious global warming that might also be coming. 

Hello, I’m Roger Carlson. I wrote the books, Saving the World Before Breakfast: A Better Green New Deal, and Saving the World Before Breakfast: The Earth Alone Can Save Us.  A key theme in those books is transforming problems into parts of the solution.  Let’s start with the so-called weeds and pests that become contributors when associated with one particular tiny fern, azolla.

For centuries, East Asian farmers have raised fish along with rice when their rice fields are flooded.  At least a half millennium ago, they added floating azolla ferns (the size of fingernails) into the flood mix.  The azolla fern is an unusual plant that carries inside of itself an even tinier algae-like cyanobacterium.  The two organisms have co-evolved in a powerful symbiotic relationship: the cyanobacterium fixes nitrogen for plant growth; and both the fern and the cyanobacterium each use a different frequency band of light for photosynthesis.  Thus. The azolla–cyanobacterium symbiotic unit has more efficient photosynthesis than probably any other plant.  It makes its own nitrate fertilizer to boost its growth further, and (most importantly for farmers) some of the nitrate gets shared with the rice plants when the rice paddy is drained later in the season.

Often East Asian farmers have simply used azolla as green manure to get free fertilizer for rice production.  However, many farmers have integrated several other plants and animals along with the rice and azolla.  One well known example is that used by Takao Furuno in Japan who described his system in The Power of Duck: Integrated Rice and Duck Farming.  Furuno’s method incorporates rice, azolla, snails, bugs, weeds, and ducks in the following manner.

·         As noted, azolla provides significant green-plant production and fixed-nitrogen production to aid rice plant growth.

·         Small duck breeds eat weeds, insects, and snails, which would otherwise attack or crowd the rice shoots.  This transforms the weeds and pests into a resource.  (Note: Larger ducks and geese would eat the rice shoots.)

·         In turn, the ducks only need a little grain to get familiar with the farmer.

·         Meanwhile, the farmer reduces need for weeding labor, pesticides, and herbicides.

·         Duck motions in feeding aerate and muddy the water for better rice growth and reduction of sunlight to resurgent weeds.  Furthermore, their bumping into rice shoots cause the stalks to be stronger.

·         Azolla and duck wastes provide food for fish, such as loach, carp, and tilapia, that can be harvested or moved to deeper water when the paddy is drained in the later stage of rice growing.

·         Even weeds are useful because their deep roots bring up minerals during the fall, winter, and spring when the paddies have been drained and the rice harvested. 

·         Finally, azolla is known as the “mosquito fern” because it reduces mosquito breeding populations by more than 95%. by covering the surface of sluggish, or still freshwater bodies, preventing adult mosquitoes from laying eggs, and by reducing the emergence and development of mosquito larvae.


Applying Azolla in North America and Elsewhere in the World

The azolla polyculture example above is from East Asia, so there must be modifications for different conditions. 

1.      East Asian farms tend to be small; Takao Furuno’s farm is 2 hectares or just under 5 acres, so it can be largely run with hand labor.  Americans will often be dealing with larger areas, and these larger areas may be best worked with powered machinery of various sorts.  Implement providers need to develop equipment to collect, analyze nutrient levels, store, and mix azolla products with other feeds.   Such machinery must be tested for efficacy and durability before farmers commit to their use.

2.      Likewise, there are studies indicating that azolla can provide a significant percentage of animal feed (ranges from 10 to 30%) and even food for people.  However, the proponents of azolla use need more studies on nutrition values and (hopefully) lack of any serious side effects from azolla feed or human food. 

3.      Azolla is considered an invasive species in some areas of the U.S.  One should check for a species that is native in the area.  Failing that, use a species that is not hardy in the area (for example a warmth-loving variety that would be totally killed by winter frosts in New York state).

4.      An additional approach is to feed azolla to any number of potential invertebrate and vertebrate small livestock, such as herbivorous fish, snails, worms, and insect larvae to increase protein content further.  These, in turn, might be sold directly as human food or indirectly as high-protein livestock feed.  Again, this should be well studied as part of the adoption process. 

5.      Besides food and livestock feed, azolla ponds in the drainage areas of fields can do more than produce human food and livestock feed.  They can radically reduce nitrate levels in waters flowing downstream and into aquifers.  As such, they could mitigate one of those environmental irritants, visits from regulators.

6.      Last, but not least, the genetic details of the co-evolving fern and bacterium might be incorporated into other plants.  Self-nitrate-fertilizing corn and wheat crops have been a dream for decades, but there is no such thing as a free lunch. The nitrate production has always come with an energy cost paid in less production per acre.  The azolla–bacterium symbiont could provide that energy to other crops.  Food production could profitably increase while more global-warming carbon dioxide would be sucked down out of the atmosphere.  It could be part of the really green Green Revolution.


Survival Requires Adoption

Pardon my repetition from my comments and many others, but humanity needs to feed more people while dealing with potentially serious changes in climate.  Azolla–bacteria-boosted crops may become the great revolutionary new crop of the 21st Century. 



·         “Azolla as a Feed Alternative in Livestock, Poultry and Fish Nutrition,” nutriNews.com, March 24, 2022. https://nutrinews.com/en/azolla-as-a-feed-alternative-in-livestock-poultry-and-fish-nutrition/ (Accessed July 9, 2023)

·         Furuno, Takao, The Power of Duck: Integrated Rice and Duck Farming, Tagari Publications; Jan. 1, 2001.

·         Mock, Shannon, “Azolla: Supplemental Greens for Waterfowl,” Purely Poultry Blog, undated. https://www.purelypoultry.com/blog/azolla-supplemental-greens-for-waterfowl/ (Accessed April 16, 2023)

Roger Carlson
            July 16, 2023


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