How important is pH?

[Wally]

How important is the soil's pH in terms of healthy turf as compared to other factors such as fertilization or seed selection, or OM levels?

Anyone know of any studies that looked at optimal pH and turf quality?

[andy10917]

There are many factors that go into what makes a "good soil" and whether that will raise "optimal quality" grass (or plants). pH is just one of them, and it's indirect as an indicator of anything about good/bad/optimal.

Put on your seat belt - some of this may seem to make no sense, but I promise you it is all true...

pH measures the presence of Hydrogen in the soil. Exchangeable Hydrogen is always zero when the pH is at 7.0 (neutral) or above. It gets higher as the pH gets lower.

But that means almost nothing - if a soil is very sandy (the TEC is very low) it will not hold nutrients well and the grass will suffer. At the opposite end, a high TEC (a clay-based or muck soil) will hold thousands of lbs of nutrients, but the grass may not do well because there is little Oxygen in the soil and roots can't expand into the soil well.

And even if you have a TEC that's right down the middle and the right minerals/nutrients are there, they could be in the wrong proportions and still get a good pH. It still won't work right. It's sort of like a gas gauge in your car - it tells the end-result of all the chemical action and none of the details about how or why it got there.

The only thing that pH does directly is to determine the availability of some nutrients within the soil. The role that soil pH plays in soil-iron availability is worth emphasizing. The marked effect pH has on the solubility of iron is well-illustrated by the fact that at pH 6.3, soluble iron exceeds 1,000 ppm. At pH 6.5, 352 ppm is available, at pH 7.0 just 35 ppm is available and a mere 3.5 ppm is available at pH 7.5. (Note the 10-fold difference in iron concentration for each 0.5-unit pH change.) Same amount of Iron - very, very different results.

So, the same amounts of the same nutrient could be too low, just right or too high in three different soils. We try to move soils toward the best they can be given the TEC and OM% that make them up, and shoot for a pH between 6.3 and 6.8 where it is possible. Sometimes it's just not possible - there is no bag (or even 100 bags) that is going to offset 5000 lbs/A of Calcium or Magnesium. Some grasses are more tolerant of wider pH conditions than others, and some folks will tell you that grass will "do OK" at less than optimal conditions. That doesn't mean that it will be optimal - it means it will not die or will be "acceptable". Many of the members here have no intention to stop at an "acceptable lawn".

[HoosierLawnGnome]

Depends what your goal is

If you want a technically perfect soil, it's very important. but most want a nice stand of turf.

You can have a very nice stand of turf working within a pretty wide range of ph. I've seen the pictures here!

So I guess I view it more of as an indicator on the dashboard rather than an end state. Helps you figure out HOW to achieve your goal.