Q: In your recent articles you described how to take soil samples for analysis. There was no mention, however, of using probes that measure soil pH and, in some models, soil nutrients as well. I have seen these probes for sale in various garden centers. It seems like that would be the most simple way to test the soil. Are the probes not accurate?

A: The inexpensive pH and nutrient probes I see at garden centers are wildly inaccurate. They can be fooled by the amount of moisture in the soil, by temperature and by recently-applied fertilizer. Don’t depend on their readings unless you double-check by having the soil professionally tested.

Professional growers use pH pens that are accurate to .1 pH point. Check the Gemplers catalog (www.gemplers.com) for pH testers. Prices for the pens range from $50 to $100 but I consider their results to be much more accurate than from probes costing $20 or less.