Miscellaneous Meters

Gardening by the Yard : Episode GBY-904 -- More Projects »

Master gardener Paul James puts a variety of plant meters to the test.

"In a store the other day I came across a wall of meters designed to measure such things as soil pH, light, moisture levels, even fertility," says James. "And I got to wondering, do these gizmos really work?" To answer his question, James bought a bunch of the gadgets and set out to test them in his garden.

Figure A

Figure B

pH meter #1. Among some of the low-tech gizmos was this soil pH tester (figure A), which consists of nothing more than a vial and a little capsule that contains the chemicals that actually measure the pH.

According to James, it's a "piece of cake" to use. Just dig down about four inches and take a small sample of soil. Fill the vial with soil up to the first marked line. Then, carefully open the capsule and dump the contents into the vial (figure B). Add bottled water up to the fourth line, place the cap on the vial and shake vigorously. Compare the color in the vial to the pH color chart. As you can see, the pH level is right around 7 (neutral), which is fine for most plants. But just how reliable or accurate is this measurement? "Well, I had a sample of this very same soil sent off to a professional laboratory for testing," says James. "And using some very sophisticated equipment, the technicians determined my soil pH level to be 6.8, which makes this test pretty darn close and pretty impressive, too."

Figure C

pH meter #2. This battery-powered, electronic pH meter should theoretically give a more accurate reading. Using the same soil sample, James compares the reading with that of the low-tech test kit and the professional lab results. To do this test, fill a small bowl with soil and moisten it well. Slide the selector switch on the probe to pH analysis, insert the probe into the soil (figure C) and wait a minute for the result. The outcome is closer to the lab results than the vial, which James suggests isn't surprising because this method relies on electronic analysis rather than wet chemistry.

"This device also claims to test soil fertility," James says, "but there's no way that this will ever take the place of an actual lab test when it comes to measuring soil fertility." For curiosity's sake, James flips the switch to see what happens. The reading denotes his soil fertility is in ideal range.

Figure D

Figure E

Figure F

Figure G

Soil moisture meter #1. James begins with a rather low-tech model that's ideal for measuring moisture in potted plants. Little indicator sticks go into the soil halfway between the base of the plant and the edge of the container (figure D). In a few minutes, the indicator strip changes from white to green (figure E) to indicate that the soil has plenty of moisture. When the indicator strip turns from green back to white, you know it's time to water. Of course, not all plants have the same moisture requirement, so James suggests varying the depth of the indicator stick depending on the water needs of the plant in question. For plants that like to be on the dry side, such as this aloe vera, push the stick almost all the way down (figure F) to get a reading. For plants such as this fern that prefer more consistent moisture, James recommends placing the stick at a depth of around two inches (figure G). "Actually, these are pretty handy, especially for those of you that are always over-watering your house plants in the winter. But after so many years of gardening, I much prefer an even more low-tech way of figuring out when it's time to water." James sticks his finger in the soil.

Figure H

Soil moisture meter #2. For a slightly more sophisticated moisture reader, this model features a long probe and an easy-to-read gauge that measures moisture on a scale from 1 to 4. All you have to do is stab the probe two-thirds of the way into the soil (figure H). Within seconds, you get an indication of how much moisture is in the soil. After testing the plant, it's a good idea to remove the probe and wipe it clean. If you leave the probe in the soil for prolonged periods, you risk damaging the probe, which will ultimately lead to false readings.

Figure I

Soil-moisture-light meter. This last meter measures both soil moisture and the light level (figure I). The probe is attached to the meter by a cord, which makes taking and reading the soil moisture measurements a lot easier. This moisture meter works essentially the same way the previously mentioned meter works, but it has a more expanded scale from zero to 10, therefore rendering a more accurate reading.

"But it's the light meter portion of this that intrigues me the most," says James. "After all, how many times did you read a plant tag that said a particular kind of plant needed high light, low light, or something in between, but never really understood what that means?"

Figure J

According to James, this meter provides a pretty good approximation of light levels measured on an alphabetical scale between "a" and "h." To get a reading, hold the meter so that the light-sensitive portion of the meter is in the same position as the surface of the leaves at the top of the plant (figure J). Be careful not to block the light as you administer the reading.

Do these gizmos have any real value to gardeners? "I think the answer is a qualified yes," says James. "Assuming they're even marginally accurate, they're better than guessing at things like pH, moisture, and light levels. This is especially true in the case of houseplants and potted plants on the patio, which so often never last more than a year because of over-watering and too much or too little light. But don't rely on these gizmos so much that you ignore your instincts as a gardener. In my opinion and in my experience, when it comes to measuring stuff in the garden, instinct matters more than meters."

Resources
gardening gizmos
Luster Leaf Products Inc.
Woodstock, IL
USA
Phone: 815-337-5560
E-mail: info@lusterleaf.com
Website: www.lusterleaf.com
Also in this Episode

Gardening by the Yard : Episode GBY-904
•	Miscellaneous Meters
•	Plumerias and More
•	Security Plants
•	The Benefits of Diversity

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