Is there a sensor that can measure the amount of nutrients in the soil?

If there is can you please give me the link? Thank you.

The kind and amount of nutrients is probably a job that only a mass spectrometer could fully do.

Lefty

Do you need to know which specific nutrients are in the soil? Or are you looking to find the EC/TDS/PPM value? If so you can use the EC-shield from Practical Maker.

I also need to need to know what nutrients are in the soil.

To know which substances are in the solution you need some very expensive sensors... I gave up looking for a cheap alternative on that one. There aren't any...
Measuring a specific substance in a solution is difficult, but measuring them in a solid I've found out to be much much harder. The easiest thing to do is take a sample of the ground, mix it with distilled water and measure the substances, but very difficult and expensive...

Oh I see. Anyway thanks to all of you