Sensor/Module to read the soil state


I'm new to arduino world, I would like to ask if there is a sensor or module that can read the amount of fertilizers in the soil, It can be done by reading 3 things :

  1. Nitrogen amount in the soil
  2. Phosphorus amount in the soil
  3. Potassium amount in the soil

I found some of these sensors but they were like 100 bucks for each chemical element, Which is too much, Do you have a good way to get them cheap and good ?

Thanks in advanced :wink:

Think that will not be much cheaper, can't remember seeing such sensor mentioned on the forum ...

Can you post the link you have found so far? even if they are 100$, they still might be interesting.

Not cheap and good, but maybe cheap and bad.

A capacitive sensor to measure the moisture, and another sensor to measure the soil resistance. The capacitance sensor does not measure the salts, but the resistance certainly does. Those two combined could say something about the vertilizer.

I would hazard a guess that those sensors were developed by and /or for "big agriculture" where price is of no object. Optimizing those levels (fertiliser vs growth) could save them gazillions so what's a few 100$ sensors among friends?