If it's dead, why not just leave it there? The roots would be the part that makes digging difficult, and there is no point I can see in just sticking the top grass in a the compost pile. OTOH, you have some organic matter already there.

No problem using it in the compost, but why? If you have raised beds, just dump the new dirt into the raised part and let the roots do your work for you. Digging is over-rated.

But make sure the Bermuda is DEAD or it will come erupting out of the ground like a zombie.

See the link below for my method of killing.

Here is a link that might be useful: How to Kill Bermuda Grass

It's not bermuda grass I don't think, just basic Seattle area lawn grass.

The raised beds are going to be fairly low, well under a foot deep and I'm going to need the additional space below them for root systems.

The gravel area I'm just planning on killing the grass, laying down a couple layers of newspaper then bringing in the gravel.

The grass is pretty much totally dormant though, as I understand it, the roundup will do a much better job of killing if I start watering the area to be killed and spray it while it's growing. Is that correct?

Correct, R/U kills stuff by the plants growing themselves to death. Some farmers add liquid nitrogen fertilizer to the mix to make it work more quickly and effectively.

So should I add a fertilizer to the mix? I want to be sure that this stuff is really dead if I'm going to the trouble of actually killing it.

There is no good reason to spray that glyphosate product on any plant material you intend to cover with a Lasagna Bed, simply construct the bed over the area and the grass grwoing there will die (due to lack of access to light) and the soil bacteria will add the nutrients that grass contains back to the soil. Spending money on a product that is not needed is simply a waste of your money.

I tried that method with a raised bed over grass before and have had to go out daily and pull up grass shoots. It's not worth it to me to have that additional work. I'm the queen of overkill for a reason. The round-up was $20 for more than I ever expect to use and I don't need to worry about the grass coming back up and harassing me every chance it gets.

"It is extremely difficult to spray RU over a large lawn area without producing some sort of drift which can/will damage any desired plants."

I disagree because

1. at the recommended concentration, Roundup barely kills the plants that you want to kill. Often you have to spray twice to kill a plant. I have a small mulberry tree that I sprayed with roundup every year for 7 years and it just keeps on sprouting new growth (albeit deformed).

2. for grass, you can use a nozzle that produces coarse droplets that do not drift much.

When you cover the grass with four to six inches of material (whatever you are putting in the beds), the grass will die... and as it decomposes it will become organic matter which will feed the roots of the new stuff that grow in the raised bed.

You don't need round up to the kill the grass (because you are smothering it) and you don't need to remove the dead grass (that's just extra unnecessary work).

If you want to use round up and remove the grass, you could compost the dead grass... but really its unnecessary.

There is a vast difference in using RoundUp to control herbaceous plants (weeds, lawns, etc.) versus using it to control woody plants like a mulberry. At recommended application rates, RU will destroy a lawn or weeds with only one or two applications. Woody plants have much more tissue to be affected and DO require repeat applications to destroy completely, although damage can occur with just minimal spray drift. And with a coarse spray nozzle, the OP will be spraying for an extended period of time to achieve satisfactory results. A misting nozzle is far more efficient for this purpose but with a far greater chance of drift or overspray.

Although RU is a perfectly efficient way of dispatching the undesired lawn and relatively quickly, it still would not be my first choice for a large area. Too much work with too much chance for mistakes to occur.

The raised beds are going to be fairly low, well under a foot deep and I'm going to need the additional space below them for root systems.

The roots will go right through the dead grass ... trust me on this. You don't need to dig for them.

If it's not Bermuda, just bury it in the beds and put some layers of cardboard in the paths.

It does kinda depend on the grass. My lawn is creeping red fescue, and it's very aggressive in crawling its way out of mulch or even fairly deep soil added on top. I would not say that just covering up any and all grass with soil is always going to kill it. If the OP says hers comes up through, she probably needs to do something to it before covering it. I doubt she's just saying that.

I understand that much grass will die under several inches of soil/mulch, but mine has not.

Thank you toxcrusadr, it's true. I've already done a section of this raised bed, and per recommendations on this forum, didn't bother to spray, and have regretted it greatly as I'm constantly pulling grass that's coming up through 7+ inches of soil.

While in most cases smothering it will do the trick, I'd rather spray it with the round-up, make sure it's dead, and save myself the potential headache down the line that could have been prevented with $20 worth of product and comparatively little work. I'm glad to hear that the grass can be composted and will be safe to grow vegetables in.

Will this grass be a carbon source when it is dead, or should I treat it like grass clippings and assume it's more or less a nitrogen source?

I can't see the argument that spraying with roundup is hard to control it is very very easy to control spray equipment

I think the grass would be a brown because it died before you pulled it I also see no reason to bother pulling it up
I would mow it on the lowest setting spray and wait a week or a little more to make sure it is good and dead

"And don't use liquid nitrogen, even if you can get your hands on it -- it is highly volatile, readily combustable if exposed to flame..."

I appreciate factual posts, and am able to wend my way through opinions, but the quoted comment is a true eyebrow raiser. The NFPA gives it a ZERO for flammability,and in my personal experience it is used as an inert blanket in some metalurgical processes.
Do you have data upholding the quote?

alphonse - you are entirely correct :-) In my desire to clarify the statement regarding applying liquid nitrogen to RoundUp prior to application, I mistakenly assigned it properties that it does not have - guess I inadvertently combined it with the properties of liquid oxygen, which is indeed highly flammable. Since both are volatile liquid forms of gasses, neither has a place - that I am aware of - in a gardening situation.

Sorry for any confusion.