What did you use for those pH tests? If one of those soil test kits from your local garden center, they are not very reliable. I have seen those soil test kits give a pH reading of that range, 6.6 to 7.2 for vinegar, milk, Chlorine Bleach and other wide range materials.
Better for you is to contact your local office of the Texas A & M USDA Copperative Extension Service.

Here is a link that might be useful: Texas A & M CES

Yes deifinately people kimmsr links. They can give you information on the cation exchange capacity. To quote in part from the link below "...a site with high cation exchange capacity takes longer time to acidify (as well as to recover from and acidified status) than a site with a low cation exchange capacity (assuming similar base saturations)."

Here is a link that might be useful: cation exchange capacity

At the link below a chap who describes himself as an educator has started a blog on soil science called soils 101. Go down to day 4, which happens to be November 4th for his discussion of "...soil chemical properties. Specifically, I will review cation exchange capacity, pH, nutrients, salts, and pollutants."

He starts with cation exchange capacity and then goes into pH which seems to me the more meaningful progression of these things. The discussion is quite elementry. There is even a drawing or two to illustrate what is happening. One could probably grasp it if one had only high school general science and just a moderately keen mind.

Here is a link that might be useful: robertbrinkmanngarden.blogspot.com

If you live in Texas and have a soil pH of 6.6 to 7.2 consider yourself fortunate. Many folks in Texas deal with soils far from neutral.

Simply put you no longer need to test your soil's pH if it's native range is what you indicated. Soils with that pH range will grow everything other than blueberries just fine with no amendments.

With respect to the above posters mentioning things like university testing and cation exchange ratios, that stuff is for geeks who are overly concerned with trivial details that simply don't matter in the real world.

Also, the home test vials you can buy at the garden center are entirely accurate for home use. No, they aren't as accurate as a lab test, but they also don't have to be. They may not be able to tell the difference between a pH of 6.8 and 6.9, but they can tell the difference between 6.0 and 8.0 reliably. That's all you need. Your soil ranges from slightly acidic to slightly alkaline and that is just fine for most everything.

It is incredibly difficult to alter the native pH of soil. ***Incredibly*** difficult. pH is largely a function of mineral content of the soil. You can add strong acids and alkaloids like sulphur or lime to adjust, but you still can't shift pH more than a point per year without toxic (to plants) results. Also the pH shift is temporary, not permanent.

If you are really concerned about pH (and for the most part you don't need to be with a more or less neutral soil pH) you are far better off regulating the pH of your water than you are trying to monkey with the pH of your soil.

Simply put plants could care less about soil pH. To reference a common reason people try to alter soil pH, consider hydrangeas. Folks with pink hydrangeas seem to want to make them blue. Conventional wisdom is to acidify the soil to make them turn from pink to blue. The truth is the pH doesn't change them from pink to blue.

Aluminum is what changes them from pink to blue. Aluminum is a minor plant nutrient that becomes plant toxic above trace amounts. Acidifying the soil causes a chemical reaction with the aluminum in the soil which makes it available to the plant and the hydrangea the turns blue.

In other words, plants care about getting their nutrient needs met and that is the only reason most plants care about pH. There are some exceptions like potatos which may develop diseases like scab if the pH is off, but we won't get into that right now.

If we regulate the pH of our irrigation water we can ignore the pH of the soil. Plants don't take nutrients from the soil directly, they take it from the thin, aqueous layer around the roots. If we water with pH adjusted water then that watery layer is the correct pH to render the nutrients in the soil available to the plant in the amounts it needs for optimal growth.

Adding vinegar to water makes it acidic (like the rain is) and will enable one to grow most anything in alkaline soils.

Commerical blueberry growers exploit this by using sulphuric acid (strongly acidic) mixed with water to irrigate their blueberries (which need really acidic conditions to yield well) even though the soil itself isn't particularly acidic.

However, given your soil's pH range you can ignore everything I and everyone above has said. It just doesn't matter. Your soil's pH range is naturally ideal for most everything therefore you don't have to think about it.

Justaguy, you are in a lot of trouble, I'm going to watch the fur fly. BTW you are right!

justaguy2, I have seen these "home test vials you can buy at the garden center are entirely accurate for home use" give test results for Vinegar at a pH of 6.8, Chlorine at a pH of 6.8, soil at a pH of 6.8, a Salt solution at a pH of 6.8, so I would not say they are entirely accurate for home use.
Because organic gardeners should also be environmentalists no organic gardener should ever add "something" to their soil without the guidance of a good, reliable soil test because adding "stuff" to your soil that is not needed will result in polluting the environment and organic gardeners should not be contributing to that.

justaguy: It's the aluminum in soil that makes hydrangeas blue? Huh! Our native soil is alkaline so hydrangeas here are normally pink, so of course we want blue. I got 2 this summer which were blue when purchased and were almost totally pink by the end of the summer. So if I want blue, I have to use something like aluminum sulfate rather than, say, garden sulfur? I was going to try dilute vinegar. Will that work? My 82 year old mother says her mother got blue hydrangeas (she apparently had many) by dumping pickle juice on them. She said whenever they finished a jar of pickles, they dumped the ramaining brine on the hydrangeas. Will dilute vinegar work? Or do I need to use aluminum?

Karen

Aluminum is generally present in soils, but unless your soils are sufficiently acidic, the plants are unable to access the aluminum and thereby produce the blue flowers you want. Personally, I'd advocate acidifying your soil anyway that works best for you rather than heaping on aluminum sulphate, as it is pretty easy to over do and create potentially toxic concentrations of aluminum.

And it should be noted that if your soils are sufficiently alkaline in content, attempting to grow blue flowering hydrangeas may be an exercise in futility unless you can thoroughly control the soil chemistry in the surrounding area. For these types of growing conditions, raised beds with appropriate soils or containers may be preferrable to in-ground plantings.

I used the rapitest meter to test the ph of my soil, will be growing tomatoes in this area.

Here is a link that might be useful: pic

I don't intend to change the pH in my entire yard. I just thought it would be fun to try on the hydrangeas. When visiting Washington state we saw so many beautiful blue hydrangeas- in some places entire hillsides of them- so I thought I might take a stab at it. I purchased 2 endless summer hydrangeas and just wanted to see if I could do it, probably only once! I'm not likely to attempt to build new, raised beds- that's just too much work! I never buy anything like rhodies or azaleas; I have received quite a few as gifts and they never do well, and die within a few years, or I give up and just pull them out. Too much work to get them to thrive and I would rather grow plants that will do well here with little help or no help. Of course I never used aluminum for the reasons you mentioned, gardengal.

I spend a lot of time gardening and I always have beautiful flowers. For me gardening is a labor of love, and if it becomes constant labor, I won't love it!

Karen

If I remember correctly, cotton burr compost is somewhat acidic.

If you want to acidify your soil, you can use soil sulfur, but it takes a long time to take effect. As others have noted, it does not permanently change the pH, but it can change the pH for a few years. You'll probably get the best results if you incorporate the sulfur into the soil rather than just spreading it on top.

About aluminum; aluminum is found in large quantities in soils. Clays for example are composed of aluminum and silica. At low lower pHs aluminum becomes increasingly soluble. This is generally considered undesirable as it is toxic to plants. This is one of the primary reasons for liming soils and raising the pH, to avoid aluminum toxicity. Aluminum sulfate is used to lower pH because it is acidic, the fact that it contains aluminum is pretty irrelevant.