Core information ideas for overseeing lawns in the fall in Northern CA
This time of year (early to mid Fall) my lawn needs about 1” of water per week.
My lawn sprinklers deliver ~2 iph (measured)
This equates to 30 minutes of needed water per week at 100% efficiency. On a daily schedule, this is a bit over 4 minutes per day / efficiency.
New seed has no root depth per se but if done properly are under about 1/8” to ¼” or topsoil (Kellogg’s Topper or peat moss), so I would treat this situation as a ½” bucket of root depth.
My soil drains at about 1” to 2” per hour with a hold capacity of about 20%, so about 5” deep per inch of water to fill the bucket. Not overly useful for seed calculation but good to keep an eye on for saturation to avoid flooding and oxygen starvation of the lawn below the seed.
The weather during the fall varies a lot in my area from day to day, which has a huge effect on the first ½” of soil, especially if the seed has poor contact with the soil below. [Wednesday and Thursday of last week were ~90F peak sunny time with an RH of 17%, but by Saturday it had dropped to 70F]. The soil temperature is fairly constant at around 59F however. What this tells me is that I have to be an active part of the adjustments from day to day or risk over or under watering. Both are bad, but dry is worse(death).
My first mistake: I first assumed that since sunrise was around 6:30 am that I should water first at around 7am and stop around dusk. Observations showed me that this was way off. The early morning condensation on the soil made it so that the soil was quite damp even at 10AM on what would be a very dry hot fall day, even though I had not watered after 5pm the day before.
My second mistake: I tried watering with 2 & 3 hrs gaps, with 9 minutes total water per day and found that the 1/8 topsoil was overly dry to the touch after three hours in the middle of the hot day. I found that adding minutes to the run time did nothing. Running my sprinklers for more than 30 seconds at a time (with no wind) was an excessive waste, but the present Rachio minimum cyle is 1 minute (60 seconds). If I start watering at 10am, and water hourly for one minute, I use 8 minutes of water if I stop at 5pm (~200% of minimum). I found that my soil did not dry out at 60 min intervals during the day. I suspect that I could easily extend that several more minutes.
Using 8 minutes per day equates to 56 minutes per week, or just under 2” of water per week. So long as the water table is more than 10” down, this should not be a problem for several weeks, but eventually I risk saturating the entire field and flooding the soil, starving it of oxygen.
Method 1 6-8 individual schedules: I followed @tmcgahey technique (Winter Rye Grass Overseeding Schedules) of manually setting up first 6 then 8 separate start times for my lawn zones where I over-seeded. I first also set up end dates for the schedule, but found that due to the daily variably and complications, that I needed to observe it every day to ensure things were going to be on track, so I changed the end date to never until I disabled the cycles one by one to get back to regular watering from week to week (4-6 weeks, dropping one or two schedules and minutes per day/ week) that will be handled by Flex Daily. This technique works fine. It is just a bit cumbersome to initially set up.
Method 2 Cycle and Soak method: (I believe that this is an easier to set up and understand method than Method 1 above). To use this method, you need to know three numbers, and vary those numbers from week to week. You need to know Duration, Cycle Time and Soak Time. Duration is the total watering time per day (8 minutes in my case). I set cycle time to Rachio’s minimum of 1 minute. I set soak time to 59 minutes in the beginning to have the watering occur exactly on the hour so I can more easily observe it. The result is a total duration of 8 hours, starting at my start time of 10am, so the schedule would end at 5pm plus 1 minute per zone (5:04pm in my case). Elegant.
If I want 9 minutes per day, I simply add a minute to the duration. If I want to shrink the time slot to water my eight or nine minutes of watering, I simply reduce the soak by a few minutes. In about 10 days I will drop a minute in the duration and extend the soak by 10 minutes, and likely repeat the following week until I get down to 4 min when I will likely disable the schedule and re-add the zones to my flex daily schedule with 4” root depth.
