What’s the Difference Between Castings and Vermicompost?
There are two words in Vermiculture that you will hear used interchangeably: Castings and Vermicompost.
Let’s discuss the similarities, differences, and issues with the verbiage.
Castings: Quite simply…Worm Poop! Basically, it is the end result(Pardon the pun), of all material that has been processed through the worms gut, and out it’s anus. Herein lies the problem. Pure castings are rare.. In fact, I can honestly say I don’t believe I have ever seen 100% castings. In order to make castings “Pure”, you basically have to leave the worms in their excrement to the point that all available food and bedding has been processed. Once this happens, worms die. Since less than 100% pure castings (Depending on the bedding used) will work wonderfully in your garden, there is no reason to sacrifice your worms. Close is good enough.
There are no current standards for worm castings. I’ve seen products called “Castings”, that ranged from very well processed material, to what looked like peat moss…that may or may not have been touched by a worm. These lack of standards are a problem in the worm industry, and another reason to buy your castings from a pro. Otherwise, you may get a product that can actually harm your plants.
How so? Products like manure tend to be extremely high in nitrogen and high in salts. Worms do a great job processing both, but…if a good portion of the manure has not actually been through the worms digestive system, you’ve essentially just added straight manure to your soil. For some plants, this would not be a huge problem. For others, especially tender starts, you’ve just created a disaster. This is one reason why I prefer to grow worms in a neutral bedding such as paper or cardboard. If any unprocessed remnants remain, you’ve done no harm to any plants
Vermicompost: The end result of all material that has been processed through the worms gut, and out it’s anus, PLUS any uncomposted worm bedding material.
Just as you buy a steak with a little marbling, and still consider it “Steak”, you usually buy Castings with a little uncomposted worm bedding mixed in. And just as you do not want a ton of fat on your steak, you do not want a ton of unprocessed bedding mixed in your castings.
What % purity should you be looking for? I’m going to take an educated, but unscientific stab at this. If your castings are around 95% pure, your grower has done a pretty good job of letting the worms do theirs!
Tags: Castings, Vermicompost