Worm Tea and Aquaponics—Application to Aquaponics

Some methods on worm tea production and its application to aquaponics as well as current issues related to worm teas and aquaponics.

How to apply worm tea for aquaponic systems?

Worm tea for soil gardens can be applied in the same manner to aquaponic systems, namely:

1. Fertigation

• A portmanteau of the words fertilization and irrigation, fertigation is a method of crop fertilization in which fertilizer is directly infused into the water source. Since the nutrients are completely water soluble, pumps are unlikely to clog[i]. You can pour this solution directly into your aquaponic system but take note of your plants and fishes' response, e.g. sensitive fish may not tolerate worm tea.

2. Foliar application

• When it comes to some immobilized nutrients in soils, e.g. iron, these nutrients can be effectively and economically delivered to plants via foliar application[vii]. Spray a light coat onto both sides of the plant leaf[iv]. Diluting the worm tea, which might have high nutrient or high salt concentrations, may prevent leaf surface burns[ii],[iii]. As well, the longer and more complete the foliar application remains on the leaf the more effective the nutrient uptake is[v],[vi]. Moreover, multiple applications and more worm tea may be needed for larger leaves[viii].

3. A combination of fertigation and foliar application

How to create worm tea?

There are many resources, especially on the web, that describe how to create worm tea but the  Bucket-Bubbler Method seems to be commonly associated with aquaponics. Of course, other methods such as the Bucket Method and Trough Method[ix] have been used as well. The Bucket-Bubbler method of worm tea production generally follows this procedure:

1. Fill the bucket with water and aerate for 10 to 20 minutes, e.g. air stones.

2. Add compost/vermicompost nearly to the top of the bucket but do not compact the vermicompost lest anaerobic zones develop.

3. Add a conservative amount of "food," e.g. sugar, molasses, to the mixture and occasionally stir and remove organisms off the surface of the mixture. Too much food will cause the oxygen consumption from the growth of microorganisms, e.g. fungi and bacteria, to outpace oxygen production.

4. Brew the mixture for at least two to three days and then turn off the aerator and allow enough time for the brew to settle. The surface of the mixture should not contain any solids since you will want a clean decantation.

5. Apply the decanted solution to the plants in the previously described manner(s).

Final thoughts and areas for future research

• “Overuse and runoff of compost teas could conceivably contribute to water pollution[x],” so don’t abuse this fertilizer.
• Worm tea’s effectiveness, especially for pathogen suppression[xi], is dependent on the quality of the worm castings and in turn the worm castings’ quality is dependent on the materials that the worms ingest[xii].
• In one study, diluted vermicompost leachate without supplementation of nitrogen, phosphorus, and potassium (NPK) stimulated plant development, but maximum growth for maize was not achieved[xiii].
• Furthermore, studies have focused primarily on vermicomposting of common land-based farm animal waste[xiv] and not aquaculture waste.
• Due to the high number of microorganisms and multiple possible interactions amongst them[xv], it will be some time before we truly understand worm tea and its effect and potential on aquaponics.

For background information regarding this post press here.

Endnotes
[i] Shlrene Quaik and Mahamad H. Ibrahim, ‘A Review on Potential of Vermicomposting Derived Liquids in Agricultural Use’, International Journal of Scientific and Research Publications, 3 (2013), p. 4 <http://www.academia.edu/3196238/A_Review_on_Potential_of_Vermicomposting_Derived_Liquids_in_Agricultural_Use> [accessed 14 January 2014].
[ii] Shlrene Quaik and others, ‘Potential of Vermicomposting Leachate as Organic Foliar Fertilizer and Nutrient Solution in Hydroponic Culture: A Review’, in IPCBEE (presented at the 2012 2nd International Conference on Environment and BioScience, Singapore: IACSIT Press, 2012), xliv, 43–47 (p. 43) <doi:10.7763/IPCBEE. 2012. V44. 10>.
[iii] Quaik and Ibrahim, p. 4.
[iv] ER Ingham, The Compost Tea Brewing Manual, 5th edn (Oregon: Soil Foodweb Incorporated, 2001), p. 50 <http://washington.osu.edu/cuyahoga/topics/agriculture-and-natural-resources/cuyahoga-composts/Compost%20Tea%20Brewing%20Manual.pdf> [accessed 15 January 2014].
[v] K Mengel and others, Principles of Plant Nutrition, 5th edn (Dordrecht: Kluwer Academic Publishers).
[vi] Ingham, p. 43.
[vii] NK Fageria and others, ‘Foliar Fertilization of Crop Plants’, Journal of Plant Nutrition, 32 (2009), 1044–1064 (p. 1044) <doi:10.1080/01904160902872826>.
[viii] Shlrene Quaik and others, ‘Potential of Vermicomposting Leachate as Organic Foliar Fertilizer and Nutrient Solution in Hydroponic Culture: A Review’, Asian Journal of Plant Sciences, 7 (2008), 360–367 (p. 46) <doi:10.7763/IPCBEE. 2012. V44. 10>.
[ix] Ingham, p. 45.
[x] Linda Chalker-Scott, ‘The Myth of Compost Tea Revisited: “Aerobically-Brewed Compost Tea Suppresses Disease”’ (Puyallup Research and Extension Centre, Washington State University, 2014), p. 2 <http://puyallup.wsu.edu/~linda%20chalker-scott/Horticultural%20Myths_files/Myths/Compost%20tea%20again.pdf> [accessed 8 January 2014].
[xi] Ingham, p. 43.
[xii] Quaik and Ibrahim, p. 5.
[xiii] Garcia-Gomez Roberto Carlos, Luc Dendooven and Gutierrez-Miceli Federico Antonio, ‘Vermicomposting Leachate (Worm Tea) as Liquid Fertilizer for Maize (Zea Mays L.) Forage Production’, Asian Journal of Plant Sciences, 7 (2008), 360–367 (p. 360) <doi:10.3923/ajps.2008.360.367>.
[xiv] Quaik and Ibrahim, p. 4.
[xv] Chalker-Scott, p. 2.