Question
I have a pine tree in my back yard that I will be removing because the grass does not grow because of the acidity in the pine needles.  What do I need to do to to prepare the ground for grass and to reduce the adidity level in the ground?  How long do you reccomend that I wait before planting the grass or installing the turf?

Answer
The KEY to success here is how thoroughly you remove the trunk and roots.  It is essential that you eliminate all traces of Pinetree, or you will be stuck with the consequences for the rest of your life.  See that?  THE REST OF YOUR LIFE.

Reason: L I G N I N !

Lignin is strong, complex and long -- probably the toughest molecule for microbes to break down.  It takes YEARS for Lignin to decompose.  Underground, it takes MORE YEARS.

The Joint Genome Institute points out that White-Rot Fungi -- so named because they turn tough Brown Lignin into soft White Cellulose -- 'are the only microbes capable of efficient depolymerization and mineralization of Lignin':

http://genome.jgi-psf.org/whiterot1/whiterot1.home.html

Unless you have a few decades to kill, remove as much of this Pinetree as humanly possible.  And be very nice to the local White-Rot Fungi.  They and they alone are in charge of making your Pinetree stump or any other wood parts nad pieces vanish.

Some quick notes on Fungi: They are ALL aerobic.  They ALL need moisture to work.  Wood decays fastest at higher temperatures; below 50 degrees F, decay slows considerably as the Fungi metabolism drops, and at lower temps, Fungi go dormant and all work comes to a halt.  Since Black Walnut is a dense, rot-resistant wood, you can expect these Tree stumps to be around for a very, very long time, under the best of circumstances.

Cornell University scientists at the School of Engineering have studied ways to speed up the way Fungi break down the Lignin in wood.  The school published their findings, 'The Effect of Lignin on Biodegradability', and posted them online:

http://compost.css.cornell.edu/calc/lignin.html

The noted, 'Adding small quantities of Nitrogen to woody materials can increase Lignin degradation rates.'

Other authorities point out the Sugar is the perfect White-Rot Fungus food; 'feeding' those areas will help to accelerate the breakdown of the Black Walnut Wood.

Erica, don't even THINK about putting a foot or two of topsoil over those areas.  Submerging them in soil will slow down decomposition (your great grandchildren may still be dealing with this problem) by severely limiting the Oxygen available to those aerobic Fungi.  Any Grass you plant will struggle and eventually fail the way all Grass fails when planted over old Trees that are no longer there.

You need some heavy equipment that will physically, totally remove those dead stumps and their roots.  Save and compost the needles and don't worry about pH.  The pH of composted Pine Needles is around 6.5.  In a year, when it's all decomposed, this will be a terrific soil amendment and top dressing.

Southern Pines drop their needles all year, from what I understand, and can do a real number on anything Lime-loving you try to grow under them, especially Grass.  But you knew that.

After the project is done, and you're SURE that all the Pine has been removed from the site, do yourself a favor and get your soil tested.   Arizona Soil usually scores low in Nitrogen and Phosphorous.  The Cooperative Extension in your state does not do soil testing, but will refer you to:

United Horticultural Supply
4429 N. Highway Dr.
Tucson, AZ 85705
(800) 825-2474

This is a critical step that you must take in order to know what your Soil lost to the Pinetree and what was left behind.  You can't grow great Grass without great Soil.  If you were going to bake a Cake, you wouldn't just run out and buy everything in the Supermarket, right?  You would check the kitchen, look in the refrigerator, see what you need and what you don't need, make a list and go shop.  When you want to grow Grass, you have to check the cupboard and the fridge.  You have to see what's in there and make a list.  A soil test will tell you that.

And that, madam, is how long you should wait.  Long enough to get your Soil Test results back and Bake the Cake.  Work fast.  It's nearly prime time for Lawn-seeding.

Keep me posted.