- Oct 27, 2011
- Reaction score
- Victoria Australia
Good to know it is working with orchids.Well I've been using the vermicompost tea for about 3 months now (about once per week as a drench and twice a week as a spray) So far I have not noticed any negative effects. On the plants in clear plastic pots. There are pretty good clean white root tips on many plants including brachypetalum. I have also used it on de-flasked seedlings and again, no problems with disease on leaves or roots so far. I'm confident there is suppression of pathogens.
The compost is now devoid of worms. I don't know whether they died or escaped. The material is very fine and humified. No smell whatsoever and it's more than 18 months old.
That's interesting. I have used molasses as a supplement to the tea but I'm still in two minds as to whether it is of benefit or not. From what you say perhaps it's best left out? Are they adding the oat bran into the compost or after extraction?VCT's do typically contain a number of known plant beneficial microbes and adding a carbon source to the brew helps increase the bacterial content. The choice of carbon source could be important. So adding sugars, e.g. molasses, doesn't preserve the bacterial diversity as well as more complex carbon sources do. Quite a few beneficial bacteria are known to produce glucanases and/or chitinases. Some folk have used oat bran (a source of glucan).
I did read one paper where they found good suppression of root-knot nematodes (aerated pig manure VCT I think). Chitin is part of the nematode's structure and adding chitin in the form of crushed crab shells apparently results in an increase of chitin digesting bacteria which also suppresses the nematodes so I can see how that ties in with the VCT.
What other forms of complex carbs could be added to the brew?I've thought of combining a glucan with colloidal chitin as a carbon source to help the survival of bacteria in the actinomycetes section. Most known chitinase producing bacteria come from this section. Actinomycetes and related bacteria are of major importance in most terestrial ecosystems with high organic matter turn over, but they are slow growing and can be swamped out by faster growing opportunistic bacteria when sugars are provided. There is some evidence that complex carbohydrates and longer brewing times are better than the molasses recipe most often suggested.
Yes, as you say humic acids are present in the VCT. I think this probably depends on the materials used and or the time given for maturity (the fineness of the final product. I have read that naturally derived (or occurring) humates out-performed commercial preparations. Brown coal may be one potential source that can be added to the worm farm to boost these?2) One study used a combination of seaweed extract and humic acid to supplement the brew. They got good results with growth promotion but it is not clear whether it's the phytohormones in the seaweed or those produced from the bacteria in the brew. Other reports indicate that humic acid can bind and stabilise phytohormones in a composting enviroment in which they are otherwise destroyed quite quickly, and can act as a slow release system for these. Humates are present in VCT to a greater or lesser extent anyway, but it seems adding some seems to be beneficial in stabilising the phytohormone effect.
In most of the literature I've read they used composted animal manures to start the vermicompost. These outperformed other VCT made from garden refuse and leaves etc. From what I remember there was a big difference in the nutrient value between the two. Especially nitrate vs ammonium, but probably also more concentrated in micro nutrients as well due to the materials fed to the animals.If anything teas made from various animal manures seem to outperform vermicomposts in this department.
I did aerate my first few batches but no longer bother. I also read conflicting results from aerated v non-aerated. One thing of interest was the difference in bacterial and fungal species with the time used for brewing. Apparently there are some microbes which are easily separated from the substrate and others which cling much more tightly. Periodic agitation of the bag seems to be of benefit here. The pH of my final product is about 6. I did not add any lime at all. It's much easier to start with an acidic product and raise the pH if necessary later. Obviously the water used will make some difference. I have no idea why aerated tea should end up with a higher pH than non- aerated though.4) One thing that bothered me a bit was that ACT tend to end up with a higher pH (>= 7.5) than NCT although there were some exceptions to this. You may want to check the pH of the final brew as some can end up with pHs in 8 - 9 range.
There seems to be enough evidence out there which attributes pathogen suppression (mildew, anthracnose, pythium etc) directly to microbial diversity and predation. When we add up the other benefits from pest suppression (aphid, mealybug, mite etc) nutrient content and availability, chemical growth factors (hormones, vitamins etc) along with pathogen inhibition, It could almost be viewed as the missing link between natural eco-systems and artificial cultivation if we can get it right.Furthermore diluting the tea too much has been shown in some studies to completely eliminate any beneficial effect. This makes me wonder whether the whole benefit of vermicomposting is all down to phytohormone content more than it is about providing beneficial bacteria ... and it was the latter possibility that got my interest in the first place.
PS, My compost was made up of the following: Dried Oak leaves, bamboo leaves, cow manure, some rotted hardwood and dried grass as a base. Soya bean meal, Canola meal, blood and bone and some seaweed extract.
Myxodex, have you read this one yet?
A very good question about the longevity of the benefit, for which I suspect we do not have an answer. I'm setting up to do some experiments with colloidal chitin, amorphous cellulose and possibly beta-glucan. Many of the protective PGPR's make extracellular enzymes to degrade these polysaccharides (PS) and I'm going to try these as the C-source in making the tea. I will then be able to test the tea for chitinase producers in the final VCT. If positive then adding a small amount of these PS's to the fert regime may help to keep the PGPR's going. The idea of feeding the PGPR's, not just the plant could be a bit crazy, but I've started making my own fert which contains both organic acids and amino acids and seen a slight improvement in growth. The limiting major nutrient for PGPR's will be a carbon source.Very interesting read guys. I have never used VT on orchids but on various other crops it works very well. You say you have not noticed any negative effects, but is there any positive effects above and beyond your usual fertilizer regime prior to using VT?
I will say this ... if I have to drench once a week and spray twice a week, I don't care how good the product is that is an inefficient use of time, energy and money for a collection over 20 plants. Cost to benefit ratio is askew, and that is not factoring in time to make the tea.
I will add some ground up crab shell flakes to the vermicompost along with some composted horse manure ( a good source of cellulase degrading bacteria ). I'm going to try making VCT brews with colloidal chitin and at least one other polysaccharide, probably cellulose. I might also use a small amount of kelp extract in some brews. Note that almost all of the bacterial polysaccharide degrading enzymes are extracellular and so the sugars released will be available to non-degrading bacteria as well, but it will be a gradual release dependent on the presence of the degraders, so this dependency should help prevent a opportunist (copiotroph) domination of the brew. Copiotroph dominance is more likely with molasses which is 70-80% sugars, all directly available from the outset. My basic practical outline is described below ... any suggestions/modifications will be gratefully recieved and considered. I will only be able to begin in spring/summer when the temperatures warm up, at the moment the worms are rather inactive due to low temperatures. I've ordered most of the materials to prepare the polysaccharides for use and this I can start soon.Interesting. So are you adding chitin, cellulose etc. at the brewing stage, or are you adding to the vermicompost?
Feeding microbes is interesting. I have "fed" cellulose (basically added corrugated cardboard pieces to the potting mix), and my experiment was not positive. I'll post this at one point. But chitin would be interesting.
I haven't read about ISR yet, but are there negative effects of ISR expressed all the time (when there is no pathogen threat)?