If you are just mulching with the leaves, then you should not need to add nitrogen.

I think the acidity thing is an urban myth. Yes they have tannic acid but it is so weak it barely registers as an acid. Besides the soil microbes are prepared to do what they are supposed to do with fallen leaves. Just keep them moist and they will decompose for you. I would not bury or till them.

I agree with dchall, leaves/wood chips etc. don't tie up nitrogen if they are on the surface, only when they are incorporated into the soil.

They also won't acidify your soil. Most organic matter won't. Peat moss is about the only thing I know will. Even if it did a pH of 6.8 is on the high end of ideal. Dropping to 6.5 or so wouldn't pose a problem for anything.

If you're incorporating the leaves into the garden soil you would be wise to add nitrogen. I just developed a new vegetable garden and amended the soil heavily with composted horse manure and bedding. I am spreading a two to three inch layer of shredded municipal leaves from last fall and will lightly till them into the top few inches of soil along with about five pounds of alfalfa meal or pellets per 100 square feet. The fluffed up soil and amendments will be well aerated, will warm quickly due to the incorporated air and the dark color, and the microbes can utilize the nitrogen in the alfalfa to build their populations and quickly decompose the leaves. I agree with the postings above that the pH change will be negligible.

Research done by Dr. Abigail Maynhard at the New Haven, Conn. Agricultural Research Station has shown that adding leaves to soil does not significantly change the soil pH. Research at other Agricultural Research stations has shown the same result, no significant cahnge in soil pH as a result of adding those leaves.
The only way to know if you need to add lime to your soil, and which lime (calcitic or dolomitic)as well as how much may be needed, is with a good, reliable soil test.

Well I had already added half the pile to the garden with hopes of tilling it in in a couple weeks.. I will go to the feed mill next week to purchase some alfalfa pellets for the nitrogen fix. I have very sandy soil so was hoping it would have been ok to till the leaves in now.

What I have found over the last 35 or so years here gardening on Lake Michigan beach sand is that tilling leaves into that sand is not a good idea since the tilling process mixes in so much air that the bacteria really go to work and digest those leaves and leave nothing, no humus, for the future. When I did till leaves into my sand there was never any humus the next year, until I started to just leave those leaves on the soil as a mulch and then I saw the humus level increase.

If your supply is sufficient to both till some in now and then use some later for mulch I would do that. The leaves and alfalfa will begin the breakdown process as the soil temperature rises. The well aerated tilled soil will warm more quickly and speed the process. In my gardening experience I have found that a single application of organic material is not a silver bullet but the first step in a process of soil building. As those leaves break down they will help to aggregate soil particles as well as make nutrients available and improve water holding capacity. A good mulch cover during the growing season will aid in slowing the loss of moisture from evaporation.

I have more than enough to till and mulch this season, possibly enough to even add late this fall. I think I will go ahead and do both the tilling and the mulching with some nitrogen added.

Thanks everyone