Question
I recently received a soil sample that came back with a Ph of 5.1.  I live in central VA is doing OK but it is struggling.  We have alot of clay in the soil and I know that I need to add lime to bring the Ph level up.  How much lime should I apply to bring it up to the appropriate level (7.0)?  Can I apply the lime now (June) or should I wait?
Frustrated in Fredericksburg.

Answer
WOW! A 5.1 pH?

Scott, this is your lucky day.  

Raising pH is MUCH easier than lowering it.  

And your clay soil is already high in calcium -- very good if you want to repel Dandelions and other weeds.

You're right to Scott, your grass will be gasping for air until you move that number up. Azaleas, blueberries, phlox, hydrangeas and ixora are on the Hardy Plants list for areas you don't treat.

As a rule, plant roots have difficulty absorbing Phosphorous below pH 6.5. Try growing anything at pH of 6.0 and Phosphorous becomes unavailable to most plants. Nitrogen, Potassium, Calcium and Magnesium become less effective below 6.0.  So your pH concerns are a big deal.

I prefer pelletized lime because there is less dust and you don't breathe it as much. Talcum-grade lime is cheaper and works quickly, but it has to be moistened in the bag to avoid puffs of lime smoke when you open the bag.  Pellets work slowly to correct soil and are more expensive.  You can apply lime any time of the year.  Sounds like in your case, the sooner the better.  At least you are not limited by season.

Turn lime 2 inches deep into your soil.  This is a necessary step.  Lime is not water soluable; it will not incorporate into soil as a top dressing.  You have to till it in.  After that, you have to add water -- moisture is essential for the lime to take effect.

Your soil needs to have at least 5% organic matter. Test results should also provide readings for Phosphorous and Potassium, too.  But you're going to need to add more than lime if you're going to fix the soil structure.  

There is a school of thought that advises against tilling clay soil.  In this case, that is the only efficient way to build it up.  

Note that fertilizers containing ammonium (made of Nitrogen and Hydrogen) or urea will further acidify your soil.  Decomposing organic matter also contributes.  Deciduous brown leaves, manure, compost, peat moss, humus are all excellent.  But consider all of the above as you do calculations for lime.  

Sand is sometimes recommended as an amendment.  But with sand, you have to be careful.  

Experts at Penn State point out that mixing sand and clay at any ratio of less than 4:5 will have the same effect as if you were trying to mix cement.  Organics is your only choice.

When it comes to soil conditioning, Alfalfa is world famous for its ability to turn plain dirt into designer soil.  If you can wait until autumn to seed, consider growing a summer crop of alfalfa.  

Alfalfa pours incredible amounts of organic matter into the ground, and you don't have to dig it in when you're ready to seed; just mow it down and leave the clippings on top of the soil to decompose.  

It's probably a little late to be sowing grass anyway -- new seed needs a month to grow before baking in hot weather.  

Adding lime may sound like a quick fix.  But it's not a long term solution to clay.

Why not?

Because -- to quote agricultural merchant Frostproof: "Organisms abound in an organically rich soil and break it down into a form of food the plant roots can absorb easily. The addition of organic material is perhaps the most important ingredient in healthy root development."

Your clay needs it.

So, when you finally get down to the mowing part, leave the clippings.  Earthworms and microbes will break them down quickly.  Unless of course you use those dreadful things with names like "Weed And Feed" or "Grub Control" in which case all signs of life in your lawn shall cease except for slime molds and fungus.  

The nonprofit Turfgrass Producers International (www.turfgrasssod.org) says that lawn grasses as a category actually perform best with a soil pH of 6.0 to 7.0--slightly acid.  The Northeast's most popular turf, Kentucky Bluegrass, prefers a pH of 5.8-6.5, according to Purdue University's Agronomy Extension(www.agry.purdue.edu/ext/forages/publications/grasses/k_bluegrass.htm).  Reed Canary Grass (known for its thick, coarse blades) and Tall Fescue (used in Southern lawns) are more tolerant of a wider range of soils.  You'll find that Weeds and Mushrooms need more acidic soil.  Clover does not.

There is a very good illustration of the role of pH and nutrients at the Lesco website (www.lesco.com/default.aspx?PageID=72).  It includes the formula for calculating the amount of limestone you should use.  

For the rest of the yard, Univ. of Fla. Extension (edis.ifas.ufl.edu/MG092#TABLE_1) posts a chart of plants for Northern gardens (?!? go figure) and extreme pH's.  

Your yard sounds similar to the testing fields used in 1985 by Penn State to study surface application of lime to a former cornfield with a 2 inch soil pH of 4.5.  You can find a report about the study at the Clemson Extension website(hubcap.clemson.edu/~blpprt/pdf/acidity2.pdf#search='when%20lime%20soil%20pH').

Good luck with your project.  Let me know if you run into any problems.