Vermiculture; Phytotoxic Leachate & Leaded Castings

Apparently vermiculture leachate can contain phytotoxins, who knew? Personally I’ve never had a problem, I wonder if my aerated design creates these phytotoxins as I germinate with mine all the time and apparently that’s how you can test for them. I’d be interested to know what the actual phytotoxins are if anyone knows. I wouldn’t be surprised if they’re phenols[2] from fermentation like in Bokashi.

Phytotoxin is an umbrella term that refers to substances (known as phytotoxic substances) that are inhibitory to the growth of or poisonous to plants.

phenol red broth.png

Apparently pools and spas use Phenol red pH test solutions. Sweet.

Anyhoo, apparently[1] you can also test for phytotoxins in the leachate by simply germinating some seeds in diluted leachate 10:1 and compare with another using just water.

Kitchen waste is said to reduce germination even in mature kitchen vermicastings so I’ll have to try this. Again, I’ve never had a problem with my flow-through bin design with holes everywhere. Yes some worms get out, and no I don’t mind; see below.

vermicompost germination.png

Apparently it takes about 8 weeks till maturity and the more mature the vermiculture leachate the higher the germination rate.

Nitrate levels also decline with maturity.

vermicompost pour-through.jpeg

Check out Vermicompost validity for more.

This is why I prefer using my kitchen-fed vermicompost leachate on my seedlings that don’t need much nitrogen yet.

Leachate contains nutrients like potassium and magnesium along with plant growth regulators[2] such as IAA and gibberellins, the most potent of the regulators. Magnesium and the growth regulators aid root and cell elongation too, especially with seedlings. And when worms are fed chicken bedding waste apparently you get even more growth promoters. I sometimes use my guinea pig waste for this reason. It also adds straw, a carbon source, and has the added benefit of sucking up water, maintaining moisture levels and reducing carbon loss. I’ve noticed mycelium hyphae covering the straw within days.

Mixed with soil I find 10% vermicastings seems to produce great results.

I’ve also found that keeping my worms moist is the most important part of caring for them. So in my temperate environment mine sit out in the rain under some trees with a bucket underneath for the leachate. So as long as it rains the worms are kept moist and I get leachate. Sometimes when it’s dry or I want additional leachate I’ll pour rain water through.

I’ve also been using extremely mature year old vermigoo as a microbial inoculation, by making a tea and pouring it around the place. I call it vermigoo because it’s super sticky gooey stuff and I want whatever microbes make that sticky goo in my garden soil holding soil aggregates together!

For my starter worms I collect them from the garden. No need to introduce foreign red wriggler species here. The wrigglers, as are some other species, known to accumulate lead in their bodies and castings. I calculated from research I read they can contain levels up to safe Australian lead handling standard levels, though I read recently those standards may have even been tightened…

This is why I let my mature worms escape if they can find there way out through the mature material and holes of my system (most don’t). I also figure that I’m repopulating my garden with worms this way.

I do this because closed systems are concentration systems, and are best avoided.

May the worms be with you.

vermicompost analysis.png

[1] Vermicomposting of food waste: assessing the stability and maturity | Journal of Environmental Health Science and Engineering | Full Text

[2] Evidence of phytohormones and phenolic acids variability in garden-waste-derived vermicompost leachate, a well-known plant growth stimulant | SpringerLink


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