I’ve done a bunch of googling and haven’t really found much about this. Admittedly, this is a pretty advanced topic, but I’m an engineer and I like endlessly tinkering with things, my Rachio settings included.
I have 3 lawn zones and are set up as:
- Clay loam
- AWC: 0.18 in/in
- Root depth: 6 in
- Allowed depletion: 50%
I recently received a soil analysis on all 3 of my lawn zones.
For CEC, my 3 zones show:
- Front: 7.5 meq/100g, 6.0 pH
- Back: 6.4, 5.6 pH
- Pool: 4.1 , 6.4 pH
After reading this article about CEC (https://www.canr.msu.edu/news/what_is_y … e_capacity), it got me thinking. It basically states that soils with low CEC don’t hold onto anything , nutrients or water, very easily.
Right now, my front yard (highest CEC) is still all completely green at this point in the California summer, even the portions that get 7-9 hours of sun per day. My back yard (mid CEC) is green in the shady areas, and green/brown in the sunny areas. My pool area has the lowest CEC out of the 3 zones, and easily contains the most brown/dormant grass of the 3.
Since lower CEC soils don’t hold water as easily, does it make sense to drop my AWC of my back yard zone a bit, and my pool zone a decent amount, to try to counter-act this? It’s still putting down the same amount of water per week, but does so less at one time, but more frequently. If I’m dropping 0.18 in/in of water on my pool zone, wouldn’t a low CEC mean that a portion of that is wasted since trickles below the grass root zone quicker than a higher-CEC zone?
Notes:
- I’ve performed multiple irrigation audits and my in/hr settings for my zones are right on the money
- I am looking into organic matter to try to raise the CEC of my back/pool zones. This is just a temp fix for the next year until I get my next soil analysis.
- The web soil survey says I have sandy loam (AWC 0.12), but when using 0.12 for all the zones, I’ll pull a soil plug sample after watering and the only top inch or two is moist, which is why I have it set to clay loam / 0.18 AWC.
