Skip to main content

To Save Water ...Measure Soil Moisture

This time of year, every California gardener becomes an irrigation specialist.  What doesn't get irrigated doesn't live - it's as simple as that.  Here in San Mateo, we had 4 1/2 inches of rain for the entire season!  There is not a lot of moisture to go around - so our use of water in the garden must be optimized.

We learn so much about the garden just by putting our hands in the soil - but our fingers aren't long enough to really tell what's going on in the root systems of our plants.  For the past month, I've been experimenting with three different Soil Moisture Meters to help configure our irrigation control settings.  Here's what I've found:

1) The Optimal Level of Moisture: You Decide

There are so many different variables that go into soil moisture: organic composition, soil grain type (ie. sand, clay), amount of daily sun exposure, type of plant.  In starting to measure moisture, I quickly realized, for example, that I was watering all of my grow bags at the same time - which was resulting in my pepper plants being overwatered.  And by moving the grow bags to a potting mix from a garden soil mix, I could see in the meter readings that the bags were retaining more moisture.   The meter has given me valuable feedback on my watering habits and the gardening materials I use.

Remember that as you change variables in the garden, your moisture levels will also change - and the best way to gauge that is through actual measurement.  The meter won't tell you what the optimum moisture level is.  That's for you as the gardener to decide.  

2) Favorite meter: REOTEMP 15" ($32)

REOTEMP 15" Moisture Meter

The REOTEMP Moisture Meter allows you to calibrate it to your optimum level of soil moisture.  So when you measure the level of moisture in the tomato bed, a reading of "5" tells you it's exactly where you want it to be.  
A reading of "4" tells me the bed is a little drier than optimal.

This is accomplished by hydrating the soil to the optimum level, inserting the REOTEMP meter into the bed and turning the calibration screw on the back of the meter to have the meter read "5".  Going forward, all of your readings are based on a comparison to the optimum level that you've pre-determined.  This is a game changer in terms of being able to consistently maintain an optimum level of moisture.

The REOTEMP calibration screw

At 15 inches, the REOTEMP probe is also twice as long as the other meters I tested - which allows you to measure deeper into the root zone.

The REOTEMP probe is about twice as long as the others.

Because the REOTEMP meter can be calibrated, everything you measure is based on the conditions to which the meter is calibrated.  In my case, I calibrated to the tomato bed, which means that, as I measure all of the other beds in the garden, the readings are a comparison to the optimal tomato bed moisture level - which isn't ideal.  This is where the other meters become useful.

3)Always carry one of the less expensive meters in the garden

The other two meters I tried were the KINCREA ($11) and XLUX soil moisture meter ($13).

You'll find these meters under a variety of brand names.  Both do not use batteries (the REOTEMP uses one AAA battery) and operate somewhat similar to a temperature thermometer.  Of the two, I prefer the XLUX meter simply because of the rounded shape.  It just feels better to carry around.  

I've found these especially useful in monitoring grow bag moisture, as they are small and easy to carry and their smaller length isn't as much of an issue with grow bags.  After a few times inserting the probes, you do start to get a sense for what the meter considers "Dry" or "Wet".   

Most important, carrying one of the meters with you in the garden goes a long way to prevent you from making soil moisture determinations just by looking at the soil surface (I'm guilty of doing this all the time).  It only takes a few seconds to get valuable information that can prevent you from overwatering - which saves H2O.

4) Location of Drip Emitters is Key

Because drip irrigation can be targeted to a single spot, you really have to keep an eye on the location of your emitters.  With a soil moisture meter, you'll see where the irrigation is soaking in and, importantly, where it isn't.  It's so easy to put the irrigation system on a "set & forget" mode - which could mean your plants aren't actually getting the water you're expending.

Hope you all have a successful 2021 Growing Season!

-Bill S.


Popular posts from this blog

Peaches and more

Yesterday we handed out the sweetest of peaches thanks to a generous donation from Circle Foot Permaculture .   Along with the quarts of peaches, we also provided Samaritan House Food Pharmacy clients a handout with nutritional information on peaches - how they impact your blood sugar - and a recipe for a Roasted Peach Parfait.  Here are links to the handout: Nutritional Spotlight: Peaches (English) Nutritional Spotlight: Peaches (Spanish) It all seems somewhat routine at this point:  gather donations of locally grown produce quickly pull together helpful nutritional information based on the week's donations In retrospect, this is the culmination of 3 years of effort to create a network of local gardeners, foragers and volunteers - with a goal of becoming a reliable source of fresh produce for lower income families struggling with diabetes and other health disorders.    While it has been known for some time that eating fruits & vegetables can positively impact a person's he

The December Garden

Snap Peas (& a garden gnome!) Beresford Park Community Garden December 15, 2021 It's hard to describe just how good the winter gardening is in San Mateo.  While most gardens across the country have long gone into a frosty hibernation - we're, at long last,  getting the rain we've been without for the last 9 months or more.  It's finally time to turn off the irrigation systems and let Mother Nature do her thing.  The new moisture is creating a full-on nutrient soup that flows through our soil, fueling an explosion of activity within the soil food web.   Fungal activity is pushing mushrooms to the surface.  Our favorite spring flowers of nasturtium, poppies, sweat peas, borage and yarrow are in a race to establish their growing territory.  And, thankfully, the newly moist soil makes pulling up oxalis, mallow and bindweed sprouts a bit easier. As you would expect, plants thriving now in the garden were initially planted out in the fall.  Those crowns of cauliflower and

Getting Started: Wine Barrel Planters

Gardening in a small, urban space requires a bit of creativity.  Our challenges are many: buildings & trees frequently block sunlight;  various critters like to snack on new seedlings and just ripe fruits & vegetables; and here in San Mateo, irrigation is a must.  To increase your probability of gardening success, consider adding recycled wine barrels into your urban garden.    Having tried many types of growing containers over the years, the wine barrel has made it to the top of my list.  My galvanized tubs always seemed to need more water than wooden barrels - perhaps due to the different heating/cool properties of the metal vs. wood?  Aesthetically, a recycled barrel looks like it's been there for years - which I love.  And the smell!  There is no comparison. Cost is definitely a consideration.  A wine barrel at Home Depot is $40 whereas a 35 gallon galvanized tub is $55.  You might say that growing in the ground is $0.00 - but in some locations, the extra 18 inches off