Hello!
I'm new but I often read the forum for a long time and now i'm here 
I've a question about a sensor.
There is a sensor capable of measuring the soil nutrient compatible with Arduino?
Otherwise, if there is not, how can I do to measure of the nutrients in the soil?
I'm building a small system for automating the management of the plants on my balcony.
Thank you all in advance!
Hi, welcome to the forum.
There are so many soil sensors, many of them can communicate with an Arduino.
This is about it : Is there a sensor that can measure the amount of nutrients in the soil? - Sensors - Arduino Forum
And this (many links to investigate) : hydroponics nutrient sensor - General Electronics - Arduino Forum
What do you want to measure ?
Should it be an industrial/agriculture sensor, or something simple to test it at home ?
Hello! Thank you for the answer!
The sensor that I'm looking for is one for home use and one for agricolutural use in another land. There is difference between for home and agricoltural use?
I'd like to measure the amount of nutrients(nitrogen,potassium etc... )in the soil. Is there a sensor that can does this?
Or, if it not exist, how i can measure that nutrients with Arduino?
Thank you!
For industrial/agriculture use, I'm thinking about sensors that can be in the ground for years, with a strong cable, and ment for automatic systems and so.
For home use, it might be a possibility to measure the moisture and also the electric conductivity with two metal pins. I think that is not accurate at all.
The subject and your question is clear, but sadly no one else answered this topic 
Perhaps you could ask it on other forums, like farming or urban vegetables growing websites.
A normal sensor would have a microcontroller inside with some kind of serial interface. An Arduino can communicate with those. Maybe a small converter board is needed for RS-232, but that is often not needed.
Try Google with the name of the salts: soil sensor potassium nitrogen
Thank you very much!
Now i've this sensor:
http://www.seeedstudio.com/depot/Grove-Moisture-Sensor-p-955.html
Is good to do this "measure the moisture and also the electric conductivity with two metal pins"?
I'm not expert... I search with "oil sensor potassium nitrogen" but the results are only scientific papers.
Can you give me some link where I can learn about this sensors or how with electric conductivity I can measure the nutrients in the soil?
Thanks for your patience and kindness.
Those are two metal flat "pins" int the soil. It measures the electrical resistance (which depends on the moisture and the nutrients/salts).
A capacitive soil moisture sensor measures only the moisture. And a real moisture sensor measures also only the moisture.
The two could be combined to have an indication for the nutrients/salts.
For hydroculture, two conductive strips (metal or something else) can be placed on the botton. They will be submersed. The resistance is an indication of the nutrients/salts.
However, at the moment I can't find a project with it yet.
I'm sure that cheap meters use other methods as well. Perhaps with two different metal pins.
The meters to measure EC and TDS use two pins to test the conductivity. I doubt if the TDS can be measured in soil. They seem to measure it in a bottle with water (taken from the soil).
EC = Electrical Conductivity.
TDS = Total Dissolved Solids.
Salanity = amount of dissolved salts
A meter with an interface is for example this one : http://www.jenway.com/product.asp?dsl=248
Someone using a EC/TDS meter : TDS/EC sensor interfacing with arduino - Arduino Yún - Arduino Forum
Do you want to measure the individual nutrients, or only a global number for nutrients ?
I'm sorry, I assumed it was easier to find projects and sensors. I think you need someone else with more knowledge about it.
Thank you, you are helping me really.
Do you want to measure the individual nutrients, or only a global number for nutrients ?
Individual nutrients is the real goal, do you think is possible? And how?
And measure global number for nutrients is easier to do?
Thanks a lot again.
For the individual nutrients, I think a labolatory is needed. I can find all kind of patents and research projects. But it seems there is not a ready product yet. Perhaps this one comes close : http://metos.at/page/en/products/22/metos-npk---the-future-game-changer-in-modern-soil-analysis
I'm out of ideas, sorry.
Don't warry, rather, thank you very much for all the help you gave me.
I'll search something with the informations that you have gave me!
Thank you very much again!
Few years ago I had paid a couple of thousands of dollars to soil analysis labs for N, P, K values.
But now there are automated on site NPK Soil Sensors available like this one
It measures N, P and K values all 3 in units of 1 milligram per kilogram (mg/kg) or milligram per litre (mg/l) and is IP68 waterproof rated.
It can be easily interfaced with a PC or arduino.
I wish this existed during 2015, I could have saved thousands of dollars and time going back and forth to soil analysis labs.
alexanealessia:
Hello Rbenson, you can use the Ubibot WS1 Pro wireless sensor for measuring the nutrients in the soil.
Not only are you responding to a thread of >4 years old, the sensor you mention measures a lot but that does not include soil nutrients.