I am aware of a similar topic in another thread which is now closed and seen the good and bad responses in that thread. There seems no viable solutions out there yet or not created, hence I wanted to recheck if there is anything out there.
For those, who think this is unnecessary, overkill, pay for lab test etc. I politely request them to not comment on this thread as I understand you have not solution to post or positive suggestions to answer the request please. And for the record I do have a use case for it.
I see a cost effective NPK (or multi nutrient) soil sensor to be a game changer is lot of places in the world especially developing and poorer countries. This could help farmers optimize the yields and take actions before it is too late.
Now, my use case is for a multi crop/tree plantation that has high value plantation that needs monitoring. So a Mesh network with Multi Nutrient soil sensor will be fantastic. I have look at Particle.io and need to find a soil sensor.
I have look at the suggestion in other posts which does not resolve my problem. I have also downloaded the research papers provided on this topic but there is no practical way to get this implemented i.e. a sensor which can provide values. I also saw the colour detection but does fall short of how we will detect under the soil and so on.
Since this will have huge benefits for farming I am resurrecting this topic so see if there are any new developments in this area.
Thanks and appreciate your positive inputs.