May I know where I can find a tutorial in making arduino project in creating NPK and Ph
if you do a web search for arduino ph and arduino npk you will get plenty of links
I have used the EZO pH and DO sensors which are easy to interface using I2C
make sure you test each sensor in an individual program before attempting to combine them in a single program
any other project requirements you have not mentioned? e.g. WiFi, Bluetooth, etc