Measuring & Control — Soil Meters

Measuring in the substrate answers a different question from measuring your feed water. You already know what you gave; what you want to know is what is still in there. That decides whether you water today or wait another day, and it is the reading most often taken by feel.

Tension rather than a percentage

The Blumat Digital Tensiometer reads not a moisture percentage but tension: how hard your plant has to work to pull water out of the substrate. That is the better measure for whether to water, because the same moisture level demands a very different effort in coco than in soil. A percentage has to be learned per medium; a tension figure says something directly about the plant.

Placing it is a one-time job

Where you put the probe decides what you measure: too close to the edge of the pot and you read the driest spot, too close to a dripper and you read the wettest. The inserter pre-bores the hole so the tensiometer goes in without breaking roots, and it fits the Tropf-Blumat Maxi as well. The protective cap shields the head from whatever flies and splashes around a grow room. The Blumat irrigation system itself is under Growing Systems.

The Fertometer measures something else

The Fertometer is not about water but about feed: it tracks a potted plant's nutrient status through the season, so whether anything remains of what you gave earlier. That is useful in soil, where a reserve sits in the medium being slowly used up, and where you only see it on the plant once it is too late.

For pH in your substrate

Those are not here but under pH Meters, because it is the same meter with a different tip. The Bluelab soil pH pen, the Multimedia pH meter and Milwaukee's MW101 with soil probe read in soil, coco and rockwool. To read EC and moisture in the medium at once, the Bluelab Pulse is built for it and sits under EC Meters.

Frequently asked questions

Does this replace lifting my pot?
On a single pot, not really, because weight is a fine measure once you know it. As soon as you have several pots, or pots of different sizes side by side, lifting becomes guesswork and a reading does not.

Does the tensiometer stay in the pot?
That is the idea, because you want the trend rather than one moment. That is also why the inserter and the cap belong with it: once placed properly you do not want to keep moving it.

Does this work in rockwool or clay pebbles?
Tension is meant for a medium that holds water. In clay pebbles, where most of the water runs straight through, the reading says less and you steer on your watering frequency and on what comes out of the tray instead.