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Living in dry California, we are about to redo our front yard with native plants only, each of which is getting a drip, for about a dozen plants per irrigation channel.

I'm trying to to figure out a good way to determine whether the plants will get enough water, while attempting to not water any more than necessary (this being California in a drought)

Naively, I'd say "let's give every plant a moisture sensor, bury the wires with the drip irrigation tubing, and have the controller figure out how long to run each channel based on the needs of the driest plant".

Has anybody ever done such a thing, without breaking the bank? If not, how would you go about doing it?

Thanks!

Update: The gardeners are redoing our front yard as I type this, but I haven't found a good approach for measuring moisture. For now, I'll have them bury sprinkler wire along each of the drip tubes; if and how it will be connected I don't know yet.

If I find the time, I'll create some moisture sensors similar to this and hook them up with some version of the 1-wire protocol, which requires very little cabling, so my sprinkler wire should be sufficient. A Raspberry Pi or such would collect the data in my garage, and publish it via WiFi. This would join my Rasberry Pi-based pool timer which has been in production use for >2.5 years now.

If you read this, even a long time from now, and are working on something similar, please get in touch. I'd love to collaborate!

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I would say that simply installing the drip irrigation system is really where your water savings is. Honestly, the water volume that you would save with all the extra effort of setting up and maintaining outdoor electronic monitoring would be pretty negligible, even if you really knew what you were doing.

I would just talk to the nursery about how much water they should be getting and keep an eye on it. Alot of variables come into play including the sandiness of the soil, and the heat of the noon sun, but your native plants should be pretty drought-tolerant so you'll probably be okay letting the soil dry out during the day. In fact, depending on the plant, it might even be advisable.

That said, if you still want try your moisture sensor idea if only to geek out on perfect plant watering, by all means come report back your success. I'd be interested to know how it works out for you!

  • This may very well be a geek-out kind of thing ... in particularly because I can't find anybody else who has done this for a front yard (plenty of people have for their potted plants), I can't find any suitable sensors, and I'm not planning to geek out to the degree necessary to create my own sensors from first principles :-) – Johannes Ernst Sep 11 '15 at 19:27
  • True. You may be able to get some help from a local industrial irrigation supply store. I'm sure some folks at one of the ag universities like UC Davis or Cal Poly would know exactly what you are looking for. What part of CA are you in? – Adam Starrh Sep 11 '15 at 23:02
  • Sunnyvale / Silcon Valley. – Johannes Ernst Sep 12 '15 at 22:18
  • Ah well if someone is doing per-plant moisture evaluation in their front yard, I imagine they would live near you ;) . Hopefully they find this question! – Adam Starrh Sep 12 '15 at 22:45
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    For example, how cool would it be if open source principles were applied to native/heirloom seed banks, where farmers big and small could share genes and produce low-cost seeds to share. – Adam Starrh Sep 14 '15 at 17:24
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What you want to do falls under the field of smart irrigation. Here's some info from one of the vendors:

smart irrigation controllers monitor weather, soil conditions, evaporation and plant water use to automatically adjust the watering schedule to actual conditions of the site.

For example, as outdoor temperatures increase or rainfall decreases, smart irrigation controllers consider on site-specific variables, such as soil type, sprinklers’ application rate, etc. to adjust the watering run times or schedules. There are several options for smart irrigation controllers.

THE DIFFERENCE BETWEEN WEATHER-BASED AND SOIL MOISTURE SENSOR CONTROLLERS

Essentially there are two types of smart irrigation controllers: weather-based (ET) and on-site soil moisture sensors. The right solution depends on your geographic location and landscape environment.

WEATHER-BASED CONTROLLERS

Weather-based controllers, also referred to as evapotranspiration (ET) controllers, use local weather data to adjust irrigation schedules. Evapotranspiration is the combination of evaporation from the soil surface and transpiration by plant materials. These controllers gather local weather information and make irrigation run-time adjustments so the landscape receives the appropriate amount of water.

ET weather data uses four weather parameters: temperature, wind, solar radiation and humidity. It’s the most accurate way to calculate landscape water needs.

SOIL MOISTURE SENSOR-BASED CONTROLLERS

Soil moisture sensor-based smart irrigation controllers use one of several well-established technologies to measure soil moisture content. When buried in the root zone of turf, trees or shrubs, the sensors accurately determine the moisture level in the soil and transmit this reading to the controller.

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