Grass Moisture Experences

[Redwhale]

Hello Fellow Droppers,

Wonder if people want to share their experiences around grass moisture levels to help guide others as to what is working. For me the big question is what moisture level is too low, what level is optimal as I balance city bylaws on when I can water.

I would be very interested in other peoples experiences at say the 3.5” depth, what is the lowest you dry out before you are seeing grass turning brown, or what is the highest you’ve ran it and are seeing negative effects of too much water.

For me I have a 7-day average at 3.5” at just below 80% and I still get a good amount of mushrooms growing so feel I can bring that down. However I also had a few areas that seemed to be browning, but would not have thought the sprinklers or other ground conditions are materially different there.

Maybe a format for people to share?

7-day-average @ 3.5 ? / Location / Soil-type / Grass results

So for me:

78 / Vancouver or Pacific Northwest / Loamy / Seems too moist, been relying on Rachio’s auto-schedule

[homedigy-stanley]

Hi @Redwhale ,

I’ll give this a try since no one else has responded. I entered your situation into ChatGPT, and it advises that your lawn is likely too wet if the sensors are reporting 80% moisture and mushrooms are still growing. From turf science, 3.5" should ideally be in the 25–35% range for healthy root function without promoting fungal growth.

Hope this helps,

Stanley
Marketing PM
Team GeoDrops

[Marley]

Regardless of this particular meter, on any meter, the max you should be reading at 3.5 inches is 25-35% moisture in loam. This is considered field capacity which is the point the soil retains the maximum amount of water it can hold against gravity, and it’s the point where the plant roots can make the most efficient use of moisture. Anything higher is considered saturation (too much water).

Permanent wilting point at 3.5 inches of loam is 15-20%. So basically, your just refilling the 10-15% between field capacity and permanent wilt. This is regardless of location. How much water and how many minutes irrigation you require to refill that 10-15% when needed is dependent on your personal irrigation system. Hope I helped.

[homedigy-lawrence]

Hi guys - Great questions! I’ll try to create a tutorial video for this in the next few weeks.

---

@Redwhale - Long story short, there’s quite a bit of initial trial and error, but feel free to try 60-70% moisture range. Also, if you’re seeing mushrooms, try to water less frequently and water longer. Mushrooms typically grow due to surface moisture (around 1”), and not deeper soil moisture (3.5”).

---

@Marley - Glad to see a lawn enthusiastic! We’re still trying to write more user tutorials and guides, since GeoDrops is a pretty sophisticated product. In the mean time, please feel free to post more questions or comments and I’ll do my best to answer them!

First, GeoDrops App does NOT report VWC (water volume / soil volume), which is the range of numbers that you and ChatGPT are referring to. Learn more about VWC here: example online pub from University of Florida

Instead we report “% micro-pores filled with water” (water volume / micro-pore volume), which is a much more sophisticated value to compute scientifically, but we’ve found that this value is a lot more intuitive for home owners to understand:

• 100% simply means "moisture saturation at field capacity” (so it’s possible for % moisture to exceed 100%, but we don’t show that in the App)
• 0% is the same as 0% VWC

Thus, people don’t need to guess or learn about field capacity, and can simply rely on “100%” value to see if the soil is fully saturated.

Next, do NOT take online recommendation numbers at face-value. I’ll give you an example of why: GeoDrops program is the first massive-crowd-sourced collection of real world soil data in North America, and we’ve found that real soil in people’s homes are far different from the ideal soil taught in soil science classes. For example, the UoF link above has this picture:

Notice that clay soil has the widest range of water absorption in textbooks.

In reality, we’ve found that ~50% of the home owner’s clay-like soil are heavily compacted (ie, people do not aerate clay soil at home as often as stereotypical farm soil). So instead of having PAW in the range of 15% ~ 40% VWC, we only measured 15% ~ 20% for these highly compacted clay soil with little to no micropores. So water run off occurs at as low as 20% VWC.

Also, besides how much is the soil aerated, another factor to consider includes the age and length of the lawn’s roots.

Please let me know if this helps and what do you think?

Thanks,
Lawrence (CEO / Lead Engineer)

[Redwhale]

Thank you @homedigy-lawrence , this was immensely helpful. I knew deep down the other readings did not make sense (from AI/Google/etc), and of course Geodrops telling me I am 100% moisture did not mean my grass was pure water, this now aligns all the data. This helps me better understand now the difference between the public recommendations and GeoDrops, really appreciate it.

>> Also, if you’re seeing mushrooms, try to water less frequently and water longer.

I felt I was doing the best recommendation there as well, oddly enough, 1 or 2, 1 hour deep waterings a week. I need more GeoDrops, I need more data =).

Thank you again.

[Marley]

Would you recommend I click the max soil moisture when my lawn is saturated or at field capacity for the most accurate tracking in the app. Thanks.

[homedigy-lawrence]

Would you recommend I click the max soil moisture when my lawn is saturated or at field capacity for the most accurate tracking in the app. Thanks.

Yes, please definitely do that!

[homedigy-lawrence]

Originally posted by @Marley in Link

Can you please steer me in the right direction of published peer reviewed scientific literature that explains the “micro-pores filled with water” (water volume / micro-pore volume) that is used to calculate moisture readings using the Geodrop and how those readings correlate to turfgrass or other plant water needs? Thank you!

We didn’t “invent” a new measurement metric. We simply scaled VWC to something that is easier for homeowners to understand.

In case it wasn’t clear in my previous reply, let me try to explain this graphically here.

Image on the left is the same textbook image from below. Let’s take the “stereotypical” loam slice of the picture, and convert the vertical axis from decimal to percent, this will give us the image in the middle. The only thing we’ve done is change the scale. ie - we’ve done one additional work for you by detecting your soil’s actual field capacity (we achieve this by asking you to click on the “deepwater calibration” button in the App). This allows the App to tell the user that 0.28 (or 28%) VWC is actually field capacity of your soil. We then report that as 100%. The rest of the moisture values scale linearly, as shown in the image on the right.

---

So… why do we spend all the extra effort and computational power to do this?
The following image tries to explain this:

As explained earlier, not everyone aerate their soil every gardening season (for most homeowners reading this, this is perfectly fine by the way – as long as your loamy soil can hold enough available water between typical 3-4 days of watering interval, you do NOT need a perfectly aerated soil).

As explained earlier, the vast majority of homeowner’s soil we’ve been collecting and measuring is a lot more compacted than your typical textbook soil. So instead off the stereotypical ideal soil moisture range as shown on the image on the left, a typical compoacted soil has a reduced field capacity (more compacted soil → less micropores → less water that the soil is able to absorb) as shown on the image in the middle anbd on the right.

Even back in early day Alpha stage testing in 2022~2023, we’ve already learned that showing homeowners VWC is not useful, becasue people will think that they have NOT watered enough, and will keep watering (wanting to see moiture level reaching closer to 28% field capacity), but in fact this is actually NOT possible, and will result in A LOT of water run off and wasted water.

So we’ve decided tthat instead of showing VWC, it’s much more intuitive for homeowners to simply scale VWC such as “100% moisture” means the soil is fully soaked and people should stop watering.

Lastly, since GeoDrops is simply scaling VWC to better tell homeowners when to stop watering, there’s no scientific paper since we’re still using VWC after all. If you’re curious about the effect of aeration and soil compactness and why this is such a big deal on changing the soil’s moisture response, even if it’s the exact same soil composition, you can find a lot of scientific paper by simply doing a google searchj.

See: Google Search

Please let me know if this helps!

Lawrence

[Marley]

Thank you for the explanation.

~ Mike