Back in November 2009, Jeff posted an educational and amusing commentary about Harvard’s use of compost tea. Much vigorous discussion followed, and we’ll return to that topic in a moment. But first, I’d like to tell you about my morning yesterday.
In September of 2010, I received a ticket for parking longer than 2 hours in a restricted zone. Now, there was no way I committed this infraction; I had hard core proof that could not be rationally challenged. So, armed with my husband’s affidavit as to my whereabouts, as well as a dated receipt showing I was at the post office at the time when I was apparently parked several miles away, I went to court to challenge the ticket. During our briefing, the sitting magistrate told us we would need to provide a “preponderance of the evidence” to win our respective cases. For me, it was an anticlimactic turn of events, as the citing officer (whom I’d subpoenaed) did not show up, so the ticket was dismissed for lack of evidence.
And thus we return to today’s subject – use of compost tea without a “preponderance of the evidence.” Jeff took Harvard to task for buying into this “bullpucky”, I think he called it, and now Berkeley has decided to drink the Kool-Aid. One of my dear colleagues at University of Washington forwarded me a link announcing that Berkeley Botanic Gardens was adopting compost tea as an “eco-friendly fertilizing method.”
As the article reports, compost tea is being used
1) as a disease suppressant
2) to provide nutrients, and
3) to reduce the amount of water needed.
I’ve written a lot about compost tea, and I’ve reviewed journal papers on the topic as well. In a scientific nutshell, there is no solid evidence to support use of compost tea, particularly aerated compost tea, in disease suppression. Likewise, there is no evidence to support a nutritional role (I just finished reviewing a manuscript on this topic and the data were unconvincing). Finally, I cannot understand why spraying compost tea onto the leaves of a plant would reduce its water requirements. The “preponderance of evidence” is truly lacking.
Students at Berkeley have the dubious honor of supporting this nonsense through their student fees: $11,000 has been spent on a 300 gallon tank, worm composting bins, and a spray tank.
Whatever happened to using good old compost, and letting nature create its own “tea?” (Compost used as a mulch also helps reduce irrigation needs.)