Buying a soil penetrometer won't make you a soil scientist anymore than buying a telescope will make you an astronomer. But a soil penetrometer will give you a glimpse of what's going on in the ground just like a telescope will give you a glimpse of what's happening in the heavens.

On the last page of this article, you'll find descriptions of four widely available soil penetrometers, also called soil compaction testers. Although they vary in design and price, each of them can help you get a better handle on soil conditions.

Also included is a sophisticated and much more expensive machine from Veris Technologies. It combines a soil penetrometer with a device that measures the electrical conductivity (EC) of the soil. (Under some circumstances, EC reveals information about the texture of a soil.)

This rig gives a glimpse of the future when it comes to exploring root zones. Most of these machines still belong to scientists, although some crop consultants have also used them.

Scientists were also the first people to use soil penetrometers, starting some 70 years ago. In recent years, farmers and crop consultants have been using them to check fields for tillage pans and wheel track compaction. Their goal is typically to correlate compaction, if any, with crop root growth and yields.

Bob Streit, an independent crop consultant from Boone, Iowa, has used a penetrometer for 20 years. It's kind of a second line of defense.

"If we see plant health problems, we know that a poor root system may be the basic problem," he says. "We find both deep and shallow compaction from machinery traffic. Field cultivator smear layers are very detectable. Long-ago livestock traffic also shows."