
Tule (YC S14) Is a Crop-Hydration Sensor for the Tech-Savvy Farmer - jefflab
http://techcrunch.com/2015/01/21/tule-is-a-crop-hydration-sensor-for-the-tech-savvy-farmer/
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jefflab
I'm a cofounder of Tule and happy to answer any questions.

A few corrections for the technical crowd:

This technology hasn't existed since the 1800's. It is derived from a
technology called Surface Renewal that measures the turbulent transport of
mass and energy from the planetary surface to the atmosphere. The concepts
behind Surface Renewal were first developed in the 1930s by chemical
engineers. These chemical engineers developed a model to describe the movement
of gases into liquid media by fluid volumes interacting with the air-liquid
interface. In the 1990s, UC Davis researchers adapted the Surface Renewal
concept to the planetary surface-to-atmosphere interface. Recent improvements
in the technology enable Tule to measure the amount of water vapor carried
away from crop field by wind eddies.

Our technology was validated for accuracy against the gold standard research
tools used in academia, lysimetry and eddy covariance.

What truly makes our technology exciting is that we can tell farmers the
optimal amount of water to apply to maximize plant growth (yield) and plant
stress (quality). Studies have shown that getting irrigation right can
radically change yield and quality. Before our technology, farmers have never
had the feedback to optimize irrigation. This is analogous to NewRelic
locating the bottlenecks in your server performance. You can't optimize until
you can measure.

edit:

As requested, here are links to the technology:

An easy to read summary is here:

[http://edu-tuletechnologies-com.s3.amazonaws.com/Tule_Surfac...](http://edu-
tuletechnologies-com.s3.amazonaws.com/Tule_Surface_Renewal_Background.pdf)

The original academic paper is here:

[http://myweb.ecu.edu/suh/PawU1995.pdf](http://myweb.ecu.edu/suh/PawU1995.pdf)

~~~
nkurz
That wasn't at all the sort of technique I was expecting. Without knowing
otherwise, I'd presumed that you were doing something that directly measured
evaporation rate, and that the claim that it was covering a large area instead
of a single point was just puffery based on the the hope that air conditions
were constant over the whole area. This is much better.

I only glanced at the original paper, but I was lost by the end of the first
sentence: "Numerous methods exist for estimating the flux density of scalars."
Mathematically, that doesn't make much sense. Does scalar have a different
definition in meteorology? Or is this an odd translation from another
language?

~~~
tmshapland
Obviously I am unaccustomed to the waters of Hacker News. I meant to post this
in response to nkurz's question rather than the main thread. See below.

Hi, I'm Tom, the other cofounder at Tule. I developed the recent improvements
in Surface Renewal during my PhD work at UC Davis.

Examples of scalars, as the term is used in atmospheric science, are air
temperature, water vapor concentration, carbon dioxide concentration, or any
other constituent of the atmosphere.

Here is a more formal definition from
[http://glossary.ametsoc.org/wiki/Scalar](http://glossary.ametsoc.org/wiki/Scalar):

Any physical quantity with a field that can be described by a single numerical
value at each point in space. A scalar quantity is distinguished from a vector
quantity by the fact that a scalar quantity possesses only magnitude, whereas
a vector quantity possesses both magnitude and direction. Thus, pressure is a
scalar quantity and velocity is a vector quantity.

------
nkurz
Neat stuff. It's a sensor that measures actual evapotranspiration in the
field, which is essentially how fast the leaves are losing water. This can be
very useful in deciding how much irrigation is needed so that the plants are
not unduly water stressed. The link to their website in the article turns out
to be broken, but it leads to
[https://www.tuletechnologies.com/](https://www.tuletechnologies.com/).

There were a number of interesting things in their FAQ that weren't mentioned
in the article. The main one that jumped out is that contrary to the article,
the cost is not $1500 per sensor, but is a $1500 per season subscription, with
the use of the sensor being included. That's an interesting model. And I
greatly admire that they are being so clear about pricing on their site.

Also from the FAQ:

    
    
      How do we know it works?
    
      We use a recent innovation in atmospheric science from the 
      University of California at Davis to measure Actual ET. 
      This innovation was validated against lysimetry and eddy 
      covariance. From a technical perspective, Tule uses the 
      Surface Renewal method to measure how much water vapor the 
      wind is carrying away from the field. If you’d like a more 
      in depth look at the technology, please let us know.
    

Yes, I'd like to know. Perhaps some details or links could be posted here?

~~~
jefflab
Thanks for the kind words! Links posted above.

------
tmshapland
Hi, I'm Tom, the other cofounder at Tule. I developed the recent improvements
in Surface Renewal during my PhD work at UC Davis.

Examples of scalars, as the term is used in atmospheric science, are air
temperature, water vapor concentration, carbon dioxide concentration, or any
other constituent of the atmosphere.

Here is a more formal definition from
[http://glossary.ametsoc.org/wiki/Scalar](http://glossary.ametsoc.org/wiki/Scalar):

Any physical quantity with a field that can be described by a single numerical
value at each point in space.

A scalar quantity is distinguished from a vector quantity by the fact that a
scalar quantity possesses only magnitude, whereas a vector quantity possesses
both magnitude and direction. Thus, pressure is a scalar quantity and velocity
is a vector quantity.

------
vacri
The soil moisture probe comment in the article is wrong. Several years ago I
worked for an agricultural telemetry company, and we resold soil moisture
probes that were several meters in length - measuring far more than 'a few
cubic inches'. The soil moisture probes were excellent for determining when
the plants were finished 'drinking', and you could also use them to determine
how far down the roots reached.

It's interesting to see the chickenwire around the probe, too. We had a
problem with native parrots who ate everything; our weather stations had
rubberised doppler probes... eaten; plastic cable ties... eaten; anything not
metal... eaten. Probably not digested, it's just that the birds get bored and
try anything...

------
decwakeboarder
In the sign up form you list a few crops (Almonds, Grapes, Carrots, Tomatoes,
Walnuts). I'm surprised to not see the big dollar US crops on the list (corn,
soybean, wheat, cotton). Do the same principals apply to those crops as well?

~~~
jefflab
The technology definitely applies to the big dollar crops (corn, soybean,
etc), and we plan to serve those markets someday. We are starting in specialty
crops (almonds, grapes, tomatoes, etc) because these customers have a "hair on
fire" problem with intensive irrigation management and the California draught.

