Did it rain enough last night to water your garden? Have you started running the sprinklers and aren’t sure if they’re running enough? Perhaps you’re not sure that new drip system you installed is doing its job. Or maybe you just want to be more efficient and careful with your water use. How can you know moisture is getting deep enough into the soil to benefit your plants. Is there an easy way to find out?
Yes there is – a simple soil probe will do the trick.
A soil probe can be anything long and sturdy enough to penetrate the soil at least 12 inches (~30 cm.). Handmade soil probes, long screwdrivers, skewers, even the spit from an old rotisserie grill will all work.
A probe made of metal will work best and for safety it should have a handle of some sort. If there’s no handle you should wear sturdy gloves when using it. This set of 22″ screwdrivers was purchased at the local outlet of a national low cost tool franchise. It meets all the requirements and is inexpensive. Plus it’s a set so there’s one for you and one to share!
While you only need the probe to go 12″ into the soil it’s helpful if the probe itself is longer, if only for convenince. The probes are shown here with a yardstick for scale. (Yardstick = 36″=~91.5 cm.)
So you now have a soil probe, how do you use it to measure soil moisture depth? Easy-peasy.
Insert the probe straight into the soil at the spot you want to test. You’ll need to use firm pressure but don’t force it into the soil. The soil will pass through moist soil but stop when it hits dry. And this is true for any soil type, sand, loam or clay. When the probe stops, grasp the probe right at the soil surface and pull it out. The part beyond your hand towards the probe tip shows you how deep the moisture is.
Note: if you have rocky or stony soil the probe may hit a rock and stop. Usually you can hear or feel that it hit a hard object. Just adjust the probe’s postion and try again.
For trees, large shrubs and deep rooted grasses the probe showing a 12″ moisture depth is adequate. For shallower rooted plants or annuals 4-6″ is enough. Monitoring soil moisture depth is an easy way to know if your landscape or garden is adequately watered. Water is a precious resource, let’s not waste it.
To estimate how much rain has fallen on your property, check out this site: