As that straw is digested by the soil bacteria they will tie up much of the available Nitrogen and it will not be available to your plants which then will not grow very well. Probably it would not be a good idea to put the straw in and cover it with soil.

There is an old trick that has been used for many years to start new garden beds, that is similar to what you want to do. We used to cut a hole in a bale of spoiled hay with a sharp instrument, aprox 12" wide & deep. Then fill the hole with good garden soil, amended with some blood meal and bone meal, and plant right in the soil. By the end of the season, the hay broke down and was reduced to maybe 20% of it's original size, and the plants thrived on the enriched soil and decaying organic matter. There was never a nitrogen deficiency.
What you plan will work fine if you add a little extra nitrogen, and you might want to save some of that hay to mulch the top as well. The humus produced will greatly benefit your soil for next year as well.

Ron
The Garden Guy
http://www.TheGardenGuy.org
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