There is a fair amount of perlite/growstone throughout, so porosity shouldn't be a concern. As for the "real dirt" component, I feed the plants separately with liquid nutrients (aside from asparagus which receives dry nutes). Hopefully the grass will only add to the mix :). Thanks for sharing your knowledge!

You have red wigglers in your raised bed? Are you trying to compost food scraps in your raised bed, or grow vegetables? I don't think I'd till just because (if I'm reading your post correctly) you have 1000 worms in your bed.

Hahaha, yes I put various food scraps and compost in the soil. Free EWC!

I wouldn't till using a power tiller. Just by hand. Also, the worms dig down during winter ;).

It will work its way in itself. You won't have to till it.

Depends on what you're trying to achieve. If you're trying to improve soil structure, no, it won't work its way in itself. Need to till, if you want to do that. Though it's true, if your soil is mostly organics anyway. tilling it in won't really accomplish that much improvement of soil structure. If you're just trying to leach minimal nutrients out of it, sure, just leave it on top as mulch. Understand that, nutrient-wise, you won't get much out of it. Compost itself is a poor fertilizer.

Glad to hear you weren't considering taking a mechanical tiller in there!

I've had an active worm bin in my garage for about 12 years, and I use the castings in my raised beds--it's great stuff. Have you had good results with your setup?

Hah, that's awesome! Yeah, I've had great success so far. Many of the worms split town to the rest of the yard, but those that stayed are a welcome sight when I encounter them :). They do a great job of keeping the dirt loose, digesting various junk I throw in and hopefully promoting a great microbial environment. How often do you find you need to "feed" your worms?

Yes, organic matter mulch on the top of the soil does work itself in as long as you've got an active ecosystem. Those compost worms will help bring it down. Forests survive and thrive with nothing but leaves and animal droppings on top of the soil, and soil organisms mixing the organic matter down in. I have had very good results with just adding mulch on top and letting it mix itself down in.

Since you are not dealing with trying to break up clay soil or dealing with any kind of compaction issue (I am assuming that you are not walking in the raised beds), then there is no reason to till. As a matter of fact, one of the weak points in your soil mix is that it started out with very little organic life (having come from a bag). Of course, life will arrive since you have provided the right nutrients, but the last thing you want to do is destroy habitat just when you are trying to encourage bugs and microbes to populate your beds.

As for the grass clippings, they don't make the best mulch by themselves. They have a tendency to clump and repel water and/or go anaerobic and form a stinky sludge. Watch out for that. They are best combined with a woodier mulch companion like straw or chopped leaves. Together they are fantastic - each one bringing an ingredient the other doesn't have and preventing the bad side effects I mentioned. They will decompose over the season and be a nice layer of compost by next spring.

Compost worms? I have worms, but it would take years for those worms to physically transport a thick layer of mulch deep in the soil. I pull back the mulch, and there aren't any worms there. I put mulch on top of my soil, and it pretty much stays there for many months. What does get leached down is the nutrients from them. Not much, but it helps. That's what's going on in the wild. To the extent the mulch does disappear, it's because it volatilizes as it degrades. All compost does that.

If you stick a shovel in the soil next to a tree in the wild, you're not going to hit high quality gardening soil.

I have to disagree Richard - with just about everything you said haha. The soils and amenities I chose actually have a very high amount of forest humus, bark, guano, fish remains and tons of active microbes. I've been very successful with this mix in a controlled environment for years.

As for the grass mulch, it appears you may have went about it very wrong. I encourage you to do some more experimentation! Grass will not form that nasty, stinky anaerobic sludge if applied properly. The layer(s) must be allowed to dry in appropriately thin layers. As for the "water repelling" you experienced, this is exactly what makes it great at keeping moisture in and weeds out :).

Concerning the red wigglers, I have no expectation for the worms to work the mulch into the soil. That would indeed take a long while... And a lot of very active worms! My question was whether to till the mulch into my soil, or to remove it each year; that's all. It looks like anything goes.

Thanks for your input everybody.

It's best for your soil if you keep the old mulch there and if wanted add a new layer on top. The soil under natural mulch does very much improve and increase in organic matter, and in my experience most mulches do degrade on the bottom surface and improve the soil below them. Maybe it's worms moving it down there, but theincreasing organic matter is very much evident in the soil under a nice mulch.

I mix my green grass clippings with leaves or wood shavings before using as mulch, usually. It not only allows a much thicker layer to be used without matting, but it forms a good balanced mix for decomposition. By fall I rarely have much of it left.

Understand that the decomposition process essentially volatilizes organics by oxidation. Decomposed material doesn't somehow soak into the soil. It floats away. Can leach some nutrients out of it, but the carbon is gone. Poof. Mulch is mulch until it disappears. Improving soil structure is a matter of digging in organic material that decays slowly, and especially slowly in a largely anaerobic soil environment. Again, what you do with added organic material depends on what you're trying to achieve. If you want minimal nutrient leaching, just leave it on top. If you want soil structure improvement, gotta dig it in.

Honest question, since when is soil largely anaerobic? Reference?

It's a lot more anaerobic than the atmosphere, where mulch is sitting. If I buried you, you wouldn't last long. But that's a fair point. There is free oxygen down there, just not a lot of it.

Human respiration and soil respiration are two very different things. Everybody's an expert... XD

I don't know enough to say what the relevant measure is and for the normal resident organisms (which would seem to be the relevant test). No doubt there is less oxygen in soil than in air but I've not commonly heard it referred to as anaerobic.