I'd recommend you try solarization. This process uses the sun's heat to raise the soil temperature to a degree hot enough to kill a range of pests that might inhabit the soil. It will also kill existing grass and any seeds in the top inches of the soil.

First, wet the soil without saturating it to better conduct the heat. Spread clear plastic over the soil surface and bury the edges or weigh them down with something heavy to prevent the plastic from blowing away. The recommendations I have seen indicate that the plastic should be from 1 to 4 millimeters thick. In our Arizona summers, I would recommend 3 to 6 mm. Leave the plastic in place for at least eight weeks.

Here is a link that might be useful: Soil solarization

Thanks for the link. This is actually what I had been trying to do, but I had been told to use black plastic. Do you think it matters? It seems that the black plastic would raise the temp even higher. This is quite frustrating as I have worked for years to get the plot healthy only to have a bad bag of s**t ruin all of my hard work.

What is "Straw grass"?

Give me a species name and I can tell you how to kill it.

Don't use black plastic. It doesn't allow the soil to get as hot as clear. Here in the low desert, transparent or clear plastic is most effective for solarization, as the heating rays from the sun will pass through the sheet and be trapped to heat the soil below. Usually, black plastic is less effective because it absorbs and deflects part of the heat rather than trapping as clear plastic does.

Here's another link from UC Davis.

Here is a link that might be useful: Soil solarization UCDavis