Allan Balliett wrote: Boy, Elaine - This is a good one!!! > At 8:32 AM -0500 1/9/02, ron poitras wrote: > >For those of us still dowsing impaired, lab tests are important in assessing > >results. The cost of testing compost tea to determine the diversity of > >microbial life and the effectiveness of various additions to the brew can be > >a barrier to perfecting a compost tea product. You can't always wait until > >your plants are giving you signals. Does Dr Ingram have any insights on > >simple tests that could easily be performed at the farm for not much cost to > >determine quality of a batch of compost tea?
Yes, this is a good one. I'm very involved in this exact question. In fact, one tea maker has stopped talking to me because I keep insisting that he have data on whether his tea maker actually makes tea. If the brown water his machine makes doesn't have the organisms in it, then I will contest that it isn't tea. So, when you buy a machine, you need to have the tea maker show you that they can document that the machine is at least CAPABLE of making a tea with high numbers in it. They should show you a count of bacterial biomass, fungal biomass at the very least. ACTIVE bacteria and fungi would be even better becasue then you know the organisms will start helping your plants right away. Plate counts don't really help here becasue dormant, sleeping organisms that may or may not ever do anything in soil get included in the count, but most of the organisms that are doing things in soil or on leaf surfaces can't even begin to grow in the plate medium. Plate count are useful for other things, however, so don't get me wrong that you should never consider them. They just aren't useful in answering this question. So, get the data from the machine maker. Then, you want to think of one of the following ways to assess your tea: 1. Total and active bacteria and fungi: This test takes about 20 minutes in the lab. So, about 2 hours after the sample arrives at SFI, you are going to get your results back. The test is $80, minus a discount if you send the submission form and payment in with the sample, if I remember correctly. You know if the tea has the number of organisms needed to result in disease suppression. 2. Oxygen concentration; As aerobic organisms grow, they use oxygen. Thus, if you measure oxygen concentration in the tea, you can follow the growth of the bacteria and fungi. This is really useful, right now data. Oxygen probes are spendy though. From $500 to $2000 dollars. Look at the Woods End Lab web site, or the YSI website. 3. Temperature. Increase in temperature means the bactea and fungi are growing! 4. Pathogen inhibition: This takes several weeks to get the information back, but does give you an idea if you are getting the disease suppressive organisms into the tea and having them work in lab conditions. There's always a problem knowing if the same thing will happen in field conditions, so it is only an indicator. The test is spendy depending on which pathogens you test, contact BBC Labs. 5. Diversity index: Six different plate media are used, and it relates to how diverse the bacteria are, although again, a small percentage of the species are actually assessed. Consider that soil should have, oh, 25,000 species of bacteria PER TEASPOON. On these plates, perhaps a maximum number of 250 species can grow. So, not a huge percentage of the possible species come up. Again, in the lab, so what is the relation between what grows on the plates and will do it's thing in soil? Don't know. But, maybe an indicator. The work that BBC Labs needs to do is show what it means if the index has a value of 3, or 13, or 33. You have more species if the index is 33, but does that mean you have disease suppression, or will improve soil structure and cut water loss? Don't know that. But could be interesting. This test is $90. Also measure foam, color, smell. I think if you record temperature, color of the tea, smell, and foam, and learn what the tea normally looks and smells like, you can use these to know if the tea is a good one. I like to measure total and active bacteria and total and active fungi on the first three teas I make each spring, and get the smell and color down again. As long as the smell, color, foam, etc are the same with each run, then I know my organism numbers. If the tea is different, then I test it to make sure it is ok. Bio-film formation in machines is a big problem. Anaerobic anything is a serious problem - you will have pathogens sooner or later if you allow anaeorbic conditions. Hope this helps! Elaine Ingham
