pH Meter – Choosing

Q: Can you recommend a pH meter that would be accurate enough to use in my perennial garden that would not cost me an arm and a leg?

A: It depends on how you define “accurate enough”. As you know, soil pH (its acidity or alkalinity) determines how efficiently your plants absorb fertilizer. pH is measured on a 14 point scale. A pH reading lower than 7.0 denotes acid conditions. A reading above 7.0 indicates alkaline soil. Most plants prefer soil that has a pH between 5.5 and 6.5 (slightly acidic).

There are several ways to measure pH. You probably remember the litmus paper pH strips from high school. The strips change color in the presence of acid. If your eyes are sharp, litmus paper strips give a reading that is accurate to plus or minus one pH point. In other words, if you soil pH is exactly 6.0, litmus paper might be interpreted as indicating a pH somewhere between 5.0 and 7.0.

I see chemical test kits at garden centers that claim to give accurate pH readings. However, I suspect they are accurate to the same plus or minus one pH point range. I also see electronic pH probes having two stainless steel legs that are pressed into the soil to gain a reading. The readings vary greatly, depending on the amount of moisture and fertilizer present. I do not consider them accurate at all.

Professional growers use pH pens that are accurate to .1 pH point. Check the Gemplers catalog for pH testers. Prices for the pens range from $50 to $100 but I consider their results to be accurate and trustworthy.