Yeah, my initial run placed the pr at only .21, which seems way too low. If I used that number I anticipate significant overwatering due to the anticipated extra run time rachio would instruct.
I may draw out a simple zone map and look for recommendations on cup placement, as perhaps my placement was off.
Do you think I am better off filling up the moisture level on soggy zones or changing the soil type to something like loam (to allow more time between watering sessions)? We received about .6 inches of rain yesterday, and I have a rain delay on until next week due to future rainy weather this week, but the moisture level chart shows moisture levels dropping about 30-40% in one day, even though the weather has been mild (60s-70s).
Another question, and perhaps this will add some insight into my lawn’s tendency to hold moisture. My mason jar test (in which I admittedly only measured the top 6" or so of soil) revealed sandy loam throughout (4 areas of the lawn tested), which is interesting as “everyone” says we have “clay soil.” In the summer, especially in dry/hot periods, the ground does become hard as a rock. Web soil survey characterizes the soil in my area as sandy loam (two types). The breakdown of these two types are as follows:
Type 1
Ap - 0 to 10 inches: sandy loam
Bt1 - 10 to 20 inches: clay
Bt2 - 20 to 28 inches: clay
Bt3 - 28 to 47 inches: clay
C - 47 to 80 inches: stratified sandy loam to sandy clay loam
Type 2
Ap - 0 to 10 inches: sandy loam
Bt1 - 10 to 14 inches: sandy loam
Bt2 - 14 to 21 inches: sandy clay loam
Bt3 - 21 to 35 inches: sandy loam
C - 35 to 80 inches: loamy sand
Do you recommend I keep the soil type as sandy loam, or, in light of the clay subsurface, should I change the soil type?
If you are confident in your mason jar findings of what your top 6" of soil is, then i would definitely cater your settings to that. That is where your grass is growing and roots are (healthy roots may be a bit lower than 6" depending on the grass)
Did you go through these steps to find your available water number? The instructions will guide you on how to use it. After that the soil type setting will only matter for the cycle-soak function, which is also described in the link. I think that’s around step 16.
Do you know where we can find when the study was conducted? I did not go through this step yet - it occurred to me that when building our development, they apparently trucked in dirt. This area used to be a peach orchard, with very fertile soil, but my soil needed considerable amendment before anything would grow successfully. It is not the best quality soil, with a considerable amount of stones (presumably among the dirt that was brought in).
another question - what is a good starting point for bottom depth when calculating available water? If I use 6", available water is .18. At 20", it is .15.
If that’s the case, which is very common, then use the results of your mason jar test.
that’s what I assumed, but since I didn’t know how much dirt was added during construction, I didn’t know what was safer. Interestingly enough, despite always hearing that we had “clay” soil, my tests all indicated, at most, 12% clay. however, when digging further down, I have found a considerable amount of clay (but this was closer to 20" or more below the surface).
Right, which is no where close to where your grass roots will be, they will be much higher. Other roots though, definitely something to consider. No matter what you choose, you’ll keep an eye on things and can always make adjustments. I have a different soil setting for my grass vs my shrubs for the same reasons you mention. Took me some time to come up with that.
So would you then recommend using the available water calculated at 6" for the grass and, perhaps, 15" for the shrubs? Those are really the only items I have - some shrubs and grass.
I would think you’d want to water to what the soil is for the roots… because if you go too sandy/loamy in a root zone that has clay, they will dry out fast. I would definitely do grass the way your findings are. And stick to the clay numbers you are finding for the shrubs and adjust as needed. There’s no correct answer, only opinions
Thinking out loud on a subject I know nothing of, but if the clay is directly beneath wouldn’t that be what the water would have to try to drain through and potentially slow the loss of moisture in the zone? Sure there’s evap and roots taking up moisture, but a container with a cheese cloth bottom drains slower than one with a large mesh screen for a bottom.
I also know nothing of the subject, but you seem to know more than me! I am open to any and all ideas/thoughts/opinions. I have preliminarily adjusted the available water to the numbers elicited from the web soil survey based upon depth of 15" or so - is there a consensus that I should use the numbers based upon 6 or 8" bottom depth for the grass and 15" for the shrubs?
@modawg2k what do you mean to stick to the clay numbers? the majority of my soil, according to the soil survey, is freehold sandy loam with this characterization:
Ap - 0 to 10 inches: sandy loam
Bt1 - 10 to 14 inches: sandy loam
Bt2 - 14 to 21 inches: sandy clay loam
Bt3 - 21 to 35 inches: sandy loam
C - 35 to 80 inches: loamy sand
That would suggest the shrubs (if using 15" root depth) are in sandy clay loam; do you suggest I revise the soil type for that zone to reflect clay loam, or leave it as sandy loam?
So, not sure if there is a way to make this image any larger, but I drew a basic zone map on my property. My question is in how to properly set up a catch cup test. Almost all of my zones overlap, as seen in the picture, so should I run overlapping zones for 10 minutes each and then use that total precipitation amount as the amount for 20 minutes runtime for each zone? Or some other approach?
Second, what sort of moisture depletion rate should I expect? All of my soil is either sandy loam or loam (multiple mason jar tests and soil survey data). Root depth is at, on average, 6" or so (tested in multiple spots, though a bit shorter in the front yard). I see soil moisture percentage drops of about 60% in a day (86% to 28%, for example), even when it is not excessively hot or dry.
Finally, Precip rates based on my catch cup test seem low. Even though psi is high at about 70, my rotor (hunter pgp) pr came in at .41 and my fixed spray (hunter 12a) at .75 -.85. Thoughts?
@franz any thoughts or insight on the above?
You’ll want to set up cups in one zone, and then water every zone that overlaps with that zone for the same amount of time.
You treat the run time as 10 minutes, not combine them both to 20 minutes. You will setup cups in one zone, and then run each zone that waters that area for the same amount of time (i.e. 10 minute), never empty the cup, then take that full amount of water and use 10 minutes as your run time.
Those range your AW from 0.12 to 0.17, I would just select either loam or sandy loam and adjust your Available Water to something in the middle like 0.15 and just monitor.
Your crop coefficient has a great impact on this, and you are using cool season grass with the default 0.8. You can play around with this number by decreasing it to 0.7-0.75 if you want to decrease the rate at which your soil is emptied in your graph.
