jremington:
It doesn't work at all, as the nutrients of interest are colorless, but we should certainly encourage experimenters discover that for themselves.
True. This sort of sensor would be along the lines of a vitamin sensor. Techniques for doing the analysis currently involve more than just using a little probe sensor thing.
I guess someone has figured this out: https://teralytic.com/. I'm very interested in this as well.
Those people THINK they MAYBE figured it out. Or at the very least they pretend they do so. The product is not available yet... the whole "order" page is down, even.
What is also worrying is the phrase "based on soil conditions compiled by governments, universities" in the "how it works" page, and no indication on what actual sensors or NPK measurement principles are used.
wvmarle:
Those people THINK they MAYBE figured it out. Or at the very least they pretend they do so. The product is not available yet... the whole "order" page is down, even.What is also worrying is the phrase "based on soil conditions compiled by governments, universities" in the "how it works" page, and no indication on what actual sensors or NPK measurement principles are used.
True, the site seems fishy. Let's wait until they update the site. Also assuming it wont cheap, expecting at the very least $500+
bradleybradms:
True, the site seems fishy. Let's wait until they update the site. Also assuming it wont cheap, expecting at the very least $500+
Yep it is really suspicious, I study agriculture and there is no way to measure soil NPK content without color.
I have to inform y'all that there is a relatively cheap solution for NPK and even pH 
Mimseey:
Yep it is really suspicious, I study agriculture and there is no way to measure soil NPK content without color.I have to inform y'all that there is a relatively cheap solution for NPK and even pH
That one does not interface with arduino since we have to fill the test tubes again and again with soil. Right?
@bradleybradms of course XD but just the tablets to achieve solution coloring, Rapitest works same way but in a more simple way I think. Pretty interesting concept
That above sensor needs manual human operation as we need to put soil sample every-time in the test tube and then inside the color comparator chamber.
So it does not have an electrical interface to be interfaced with arduino.
On top of that, it only tells category like High / Medium / Low content of NPK.
(If you want only category information like Low / Medium / High for NPK, then there is this sensor at half the price and does NOT require filling test tubes again & again with soil)
Both previous sensors do NOT quantify in units of milligram per liter (mg/l) or milligrams per kilogram (mg/kg).
For quantification,