[Reinier van der Lee] owns a vineyard in southern California – a state that is in a bit of a water crisis. [Reinier van der Lee] also owns an arduino and a soldering iron. He put together a project the reduces his water usage by 25%, and has moved it to open source land. It’s called the Vinduino.
Its operation is straight forward. You put a water sensor in the dirt. You turn on the water. When the water hits the sensor, you turn the water off. This was not, however, the most efficient method. The problem is by the time the sensor goes off, the soil is saturated to the point that the plant cannot take it all up, and water is wasted.
The problem was solved by using three sensors. The lowest most sensor is placed below the roots. So it should never go off. If it does, the plant is not taking in all the water, and you can reduce the output. The two sensors above it monitor the water as it transitions through the soil, so it knows when to decrease the water amount and watering cycle times.
Be sure to check out the project details. All code and build files are available on his github under the GNU General Public License 3.0
At first glance this looks like a GREAT idea. However, it looks like this results in more frequent applications of smaller amounts of water, and I’ve always heard that’s a BAD idea because:
1) Roots need to dry out for sufficiently long times between waterings to prevent root rot, and to allow oxygen/nitrogen from air to penetrate the soil.
2) Water isn’t only lost downwards. It’s also lost upwards, due to evaporation from the surface of the soil. Frequent waterings increase this loss.
3) Frequent shallow waterings result in shallow root systems, as the plant has no need for larger/deeper root systems to collect enough water. Unfortunately, this means that when a deep watering occurs (naturally as rain), the plant can’t gain as much benefit from it, as the water quickly passes out of the range of the roots. This leaves the plant more dependent on irrigation water, offsetting water savings by some amount.
In fact, [Reinier van der Lee] posted this on his Facebook page on June 8th, which I consider relevant to #3:
“There is a Thompson Seedlesss grapevine in our backyard that has not seen irrigation water for months. This vine is actually doing very well, with large full clusters of juicy grapes hanging from it’s canes. From soil moisture sensors installed at three different depths I learned that deeper soil layers actually have sufficient moisture. No sprinklers needed for this one. We all have opportunities for saving water.”
There’s no better water savings than not having to water at all! I bet that Thompson has nice deep roots, adapting naturally to not receiving irrigation water. Yet [Reinier van der Lee] seems to going the opposite direction with this project.
So has this watering method actually been PROVEN to save water, either by [Reinier van der Lee] or another party? Or is it only hypothesized that it will?
Regardless, having moisture sensors at three different depths seems an unqualified advantage, even if the proposed watering method might be questionable. You can’t have too much information.
Wouldn’t applying the water where it is needed – below the surface – solve some of the problems you’re bringing up? The moisture sensors need to be brought down anyway, so the irrigation system could be installed similarly.
Yes, it would, see https://en.wikipedia.org/wiki/Subsurface_textile_irrigation.
In the raised bed gardens I built this spring, I installed a DIY version of this using drip irrigation nozzles wrapped in a layer of water-permeable landscaping fabric with a 6-inch wide strips of plastic sheet running under the drip lines. Thus far, aside from soaking the surface a couple times per week for the first two weeks or so when planting seeds or transplanting seedlings, I haven’t had do any surface irrigation. The surface stays bone dry, which, from what I’ve read, helps prevent weeds from sprouting and based on my experiences so far, seems to be true as weeds have been less than I’ve previously experienced. From about 1-3 inches below the surface down to the drip lines, the soil is damp, but never soggy, so root rot hasn’t been a problem either.
Now to build one of these and integrate it with the supply line so I can water the garden when it needs it instead of just on a timer. Great job!
Do you use any coverfoilage to prevent ground erosion? If its “bonedry” i could image that a bit of wind would slowly erode your raised beds (yeah i know very minor problem to worry about).
I hadn’t really considered the wind being an issue, but we do get a lot of strong gusty winds here though, so it could be a valid concern. This is my first year trying this (or gardening at all) so ultimately, I can’t answer with any certainty right now.
This is all speculation, but the surface texture is mostly like dried mud, so there’s kind of a crust to it as opposed to it being powdery, so maybe the wind won’t affect it as much. Also, I’m using square foot gardening methods, so the plantings are quite dense and once they fill in some, I hope the wind won’t really be much of a problem any more. I would guess that the box walls might also provide a bit of a windbreak for anything below an inch or two below the top.
In the end, I have a high concentration of compost in the boxes and so between the settling of the soil as the compost decomposes and needing to replenish nutrients as they are used up, I fully expect to need to top off the boxes with additional compost each year. My guess is that I probably wouldn’t really even notice if the wind steals some of the dry soil on top. With both beds only being 4’x8′ each and access to free compost from my city’s community compost site to refill it, I’m not as worried about as professional farmer might be.
I think you could solve 1 and 2 in software by checking the sensors every so often and having mandatory “dry” times in between the wet ones.
Depending on how many sensors you can string together and the resolution of the sensors (is it 1 to 100% or binary Wet/dry?) you could adjust your water to your drainage+evaporation levels.
If you can get weather forecasts into the system somehow you could also try to avoid watering at all on certain days.
Another thing that might help with 3 is having different layers in your planting bed maybe a high drainage sand cover over one that sponges up water for a while minimizing evaporation while you get a deeper root system that is airrated.
Good comments, thank you!
1) It will take A LOT of water to drown grapes. I have seen the Danube flood vineyards in Austria, and they came out fine. To your point, you can set the moisture where irrigation starts, and manage how deep you “cycle” the irrigation.
2) Frequent in agriculture means daily instead of up to few times a week. My vineyard management company used to come out by day to open the irrigation valves. At temperatures well over 100F you can expect evaporation loss. Now I irrigate during night hours.
3) In Southern California dry farming grape vines is not possible. I tried and failed. Drip irrigation -not irrigation frequency- promotes shallow root systems. Drip irrigation is one of the most irrigation methods, over 85%. There one side effect though that I recently discovered, weeds like frequent irrigation! I spent this weekend whacking weeds :-)
The Thompson Seedless test (home backyard) is running for half a year now, and not a good representation of soil moisture in the vineyard. The vineyard is 1.5 hour drive away, so I use my own backyard for testing as well.
The neighbors sprinklers run-off provides sufficient water for the Thomson grape.
A nice side effect for my wallet, but not usable in the vineyard.
Farmers have been using gypsum sensors and multi depth measurement with good results. Farmers in Australia are drought specialists and are big users of sensor controlled irrigation. The Vinduino project goal is to make this technology affordable by providing as open source.
Proof is in the pudding. I will keep a record of my water savings vs last year in the project update. Given weather dependencies, 25% saving is my goal for this growing season.
Off-topic, its ideas like this that venture capitalists should be throwing money at – not the next Twitter. As a woodworker I’m acutely aware of the expense of good quality wood as a result of deforestation; water consumption and conservation are just as important to pay attention to. I’d buy you a beer; these projects do man-kind good.
Sharing intermediate saving results, comparing water use 2015 vs 2014:
June 2015: 178 HCF vs June 2014: 397 HCF (55%)
July 2015: 295 HCF vs July 2014: 441 HCF (33%)
Savings are well above the 25% target AND the grape vines are doing well.
Last year we stressed the vines by reduced irrigation in the month before harvest, the is to get more concentrated grape material. Expect less or no saving in August, overall we should come close to 25%.