Sugar Not So Sweet When it Comes to Compost Tea

Different carbonic supplements induced changes of microflora in two types of compost teas and biocontrol efficiency against Pythium aphanidermatum
May, 2019
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    Sugars are known to be microbial food sources and have long been used in farming as a supplement to promote plant growth.  In compost tea, Molasses is the most often used sugar source and in known to produce a beneficial, biologically active tea.  However, there is a not so sweet side to this story when it comes to disease prevention. 
      Scientists at the Ningxia Normal University in Guyuan, China wanted to look at how compost teas brewed with different microbial food sources (Glucose, Sucrose, Starch, Chitin, Cellulose, & Wheat Straw) would affect damping off of cucumber seedlings caused by Pythium.  The scientists used two different types of compost (soy straw/cattle manure, and wheat-straw/chicken manure), and brewed teas 7 teas each (made with the six listed food sources, and one tea as a control with no food source).  Then the teas were assessed for: physio-chemical properties, enzyme activity, microbial populations and colony types, in vitro (in the lab) and in vivo (in field) disease suppressive qualities.
      What was found.... there is a significant amount of diversity in the teas and their respective attributes.  From pH, to Water Soluble Carbon, to enzyme activity, to microbial populations, the two compost types and their food sources produces a variety of results, which indicate the complexity of these dynamic concoctions.   The most stand out piece of information is that in the greenhouse studies, the teas brewed with Glucose, Sucrose, and Starch were associated with higher incidence rates of damping off.  The Chitin, Cellulose, and Wheat Straw teas showed significantly lower rates of the disease.  This leads us to believe that compost teas produced with sugars are less effective in controlling the fungal pathogen. 
      At TeaLAB, we generally use Fish Powder as a food source for our teas, and only recommend molasses (sugars) to be used in the last weeks of the growing season.  This direction has been based on our own experience, a healthy understanding of the soil food web, and information learned from the farmers and gardeners that share their experiences with us.  It is very good to see that there are scientists on the other side of the globe working to better our understanding of the brew, so that we can then make you more successful in your gardening endeavors.  Thanks to the researchers, and to you too! 

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