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A soil moisture meter is a handy tool to have when you are wanting to know when it’s time to water your succulents or cacti. It almost looks too simple, so much so that the question often asked is How does it work and what is it measuring, exactly?
A soil moisture meter tests for the electrical conductivity of the soil, and since water conducts electricity very well, moist soil will conduct more electricity than dry soil. Your meter measures this conductivity and gives you a reading of how much moisture is in the soil.
Since the readings are based on the drier soil having the least conductivity and wet soil having the most, it can only give you a general idea of how much moisture is in your soil. Even so, with practice, it can give you a good idea whether your plants need water or not.
A Soil Moisture Meter Measures Electrical Conductivity
Electrical conductivity measures how well electricity is conducted through something, and in this case we’re talking about your succulent’s or cacti’s soil.
Water is a good conductor of electricity – especially in the presence of salt ions, which in our case is always present in the soil.
The more salt ions there are – the higher the conductivity is. If there are less ions, then the conductivity would be lower.
When we are using a soil moisture meter, there are two parts required in order for us to test the conductivity in soil. First, we need the salt ions which we mentioned above, and these ions are naturally found in the soil all the time. Second, we also need water to conduct those ions.
We are not testing for a change in the salt concentrations in our soil, that part of the equation should not change at all (if it does, we have a problem with our soil), but instead, we are testing for how much water there is to transport those ions in the soil.
So since the only thing changing is the amount of water and not the salt ions, the readings we get on the meter are due to the change in how much water is in the soil.
The less water there is, the lower the conductivity of the soil and the more water, the higher the conductivity.
Why is it Important to Measure Soil Moisture?
Succulents and cacti are very sensitive to being overwatered. They also have problems with being underwatered too, but overwatering, especially, can create problems like root rot.
That is why it can be so important to make sure the soil is completely (or mostly) dry before giving them more water. I have always in the past used the “finger test” to see if my plants needed water, but that isn’t as accurate as a moisture meter.
A moisture meter can be a great tool to help us decide when our succulents/cacti need to be watered. With a tool like this we can measure much deeper in the pot to get a better idea of how much moisture there is in the soil.
If you are thinking about getting one of these meters for your indoor plants (they work outdoors, too), you could check out this one on Amazon. In addition to measuring the moisture levels, it also measures nutrients, pH, and light levels too.
Are Soil Moisture Meters Accurate?
Now that we know how moisture meters work in general, we have a pretty good idea about how to answer the question of “Are soil moisture meters accurate?”
Soil moisture meters are not accurate but can give you a good idea how dry or how wet your soil is when used correctly. The only way they can be accurate is if they were calibrated, which is not something most casual gardeners want to do.
They can be calibrated to exact scientific standards, if a person wants to do so, but it isn’t necessary for most gardeners.
The casual gardener can still get good results from their moisture meters by testing and recording what the readings are when their soil is dry and again when the soil is wet. Over time, and from experience they can then determine what the desired reading levels are needed for their plants.
We have an article that you can check out called “Succulent & Cactus Care: How to Use a Soil Moisture Meter” It talks about how to use a moisture meter and gives you tips on what to do if you have top dressings on your plant, as well as what can give you false readings.
Are Soil Moisture Meters Worth It?
With all that being said, someone might ask If the meter isn’t calibrated, is it worth buying one?
Soil moisture meters are worth buying since, even if they aren’t calibrated, they can still give you a good idea whether your succulents and cacti need to be watered or not. This is especially true if you can’t do a “finger test” due to cactus spines or if you have top dressings.
Moisture meters aren’t very expensive and can give you good results even if they aren’t calibrated. I have listed below a few reasons why I believe they are worth buying and using.
- You will get a more subjective idea over whether your plants need water. I feel this is better than the traditional “finger test” for dryness, especially since the probe can go much deeper in the soil than your finger.
- There is always the option of calibrating your meter to get more accurate results.
- It can keep your fingers from getting dirty. This is especially true if you need to test several plants throughout your home.
- It can protect your fingers from touching cactus spines. This is especially true when the cactus takes up most of the space in the pot.
- The probe is more slender than your finger and will do less damage to your plants. For example, if your plant takes up most of the space in the pot and there is little room for you to do the “finger test”.
This post was written for cactus-central.com and is not permitted to be used on other sites.