Gauge for measuring soil moisture

September 3, 2010 10:25 AM

Have you used a soil moisture gauge?

Has anyone had much luck using a soil moisture meter? I'm struggling with over- and under-watering some of my more touchy plants (I'm looking at you rhododendrons) and I'm trying to make my watering decisions more evidence based.

If you've had success with a specific model(s), I'd love to know which one(s).

posted by foggy out there now to Home & Garden (3 answers total)

I never really trusted them for plants in the ground except say to see whether the soil under deep mulch is dry or not. I know people who love them for pots though. I think the moisture content is more uniform in a pot.
posted by caddis at 10:59 AM on September 3, 2010

I've used the super cheap mechanical meter ones. Usually in the beginning of gardening season or during hot days to make sure all the drip system works. But it's more of a wet or dry tool - I don't trust the sensitivity.
posted by Big_B at 12:22 PM on September 3, 2010

Are you talking about the handheld devices, or the ones where you bury a bunch of gypsum blocks in the ground, or a tensiometer? If the handheld, you might as well just go out with a trowel and do some digging to see what's going on. The probe meters can be wildly inaccurate, because they detect the ions in the water, not the water itself. So very saturated soil can read as "drier" than drier soil, because ions are more widely dispersed. All meters can be inaccurate in soil with large particles, like forest duff (which is pretty much the optimum condition for the average garden rhodie). If they measure water tension ( a better type of meter than the probe), you need to know what type of soil you have, because water availability (what the plants can take in) varies, even if the centibar reading is the same in different soils. If you dig holes and feel the soil instead of using a meter, you get to know your soil, its texture and composition. I think this is better in the long run for the home gardener because it tells you more about the way you should be working in your garden.


Anyway, there's some very good info here about soil moisture in general, different ways of testing, and types of moisture meters.
posted by oneirodynia at 12:47 PM on September 3, 2010