Checking moisture at 24"?

I have some older citrus trees that I think I water a lot, but they regularly look droopy in warm weather…and always perk up after a good watering. I’ve been reading that I need to water citrus enough so that the soil 24" down is moist.

But how to do this? I have a good moisture meter (Reotemp) that’s about 17" long but I’ve ruined one of them (tip came off) just trying to go down 10-12". So I’m looking for a good way to check the soil 24" down without spending a fortune. Any suggestions?


If your soil is lacking in stones a good method utilizes a rod of some kind. You’ll only be able to push it into the soil as far as the water penetrated. Use it the day after irrigation before the soil firms up. Rods with a ball on top, 6ft long, and about 1/4 inch caliper are made for this purpose. But a piece of rebar works.

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If you actually wanted to get a sample of the soil you could buy a soil sampler probe. To go down 24 inches it looks like it would cost around $75, They work well but that is pretty pricey to me.

I’ve tried making my own soil sampler, but there’s a reason they are made with expensive stainless steel. I tried with cheap EMT conduit pipe, cut out a section just like the good ones have…that’s exactly where it bend in half. I’ve also tried with regular 1" galvanized pipe, without cutting out a section, and pounding it into the ground 8" was really hard. I don’t think I could get it down 24" without a big sledge hammer. Then getting it out would be really hard, and knocking out the dirt…even harder.

Fruitnut, that sounds like a good idea. When you say “push it into the soil”, do you mean by hand (ie. not with a hammer). Do you know the exact name of such a rod, I’d like to know more about this.

The theory of using the rod or probe is if you can not push it in the ground with using the handle, the soil is not moist at that level. If you have a good sandy to loamy soil, the rod or probe should go into the ground easily until it reaches the level where there is no moisture. It would not work well if you have a hard clay soil. I have seen people push the probes in sandy soil about 18 inches but it did take some hard pushing but the soil had not just been irrigated.

Gary explained it pretty well. In many soils you can easily push a rod by hand into wet soil. But you can’t push it into dry soil. So right after an irrigation you’ll be able to push the rod in as deep as the water penetrated. That assumes no big rocks.

When I was younger and working dryland crops I’d go out with a 6ft push rod and see how far down the soil was moist. Even long after any rain I could push the rod into moist soil but not dry soil. If the soil was wet down to 4ft or deeper it was set up for a good crop of dryland sorghum or wheat.

Longest probe I could find was 48 inches. That’s long enough for fruit trees.

Here’s another one I found on Amazon. Made in USA, they have a 36" probe for $16+ and this 48" one for $21. These are 1/2" diameter.