Use of PLC for greenhouse hidroponic NFT system , (loop control of PH, EC and Temp in nutrient solution reservoirs)

Good afternoon and blessings, currently I am in full execution of an Automation project of a large-scale Greenhouse complex, which uses NFT hydroponics technology, we are currently selecting the technology to automate the control of PH, EC and temp in the main reservoirs (main tank) which are 2 underground. and located next to each other.

To this end, we are locating a technology based on a single PLC that controls the PH, EC and Temp in both reservoirs and that can be integrated under open protocols (modbus tcp, MQTT or another) with a SCADA-type platform that we are installing in the complex.

Additionally, it can integrate small level control loops for stopping the suction pump to the NFT system and the solenoid valve for feeding the nutrient solution that feeds the tank.

Any recommendation for a potential solution in this matter and references?

A best thing to do would be to choose the right parts/devices like sensors probes...
Looks like the project can easily be handled by a good OEM with associated or third party Plc and scada...
Siemens for sure is good but bit expensive comparing to south Asia OEM..
But choice is to be guided by length of the project..
Standardization or not of the elements of each system..

I would choose PLC from GE SIEMENS or even Allen Bradley .
But the thing is to got kind of harmonisation and compatibty between each devices..
A good topology.. Drawing architecture of the system have to be studied first for sure..
Good luck!
Any time!
Do not hesitate to share a drawing we can advise on the topology to adopt..

The control part sounds trivial - capable by almost any PLC/PAC (Process Automation controller, designed more for process control than for the speed of their discrete input ladder scans).

My limited exposure to fish farming revealed quite stringent requirements for temperature and pH control; I don't know if plants are as fussy as pet fish are about their environment, but if that's the case then taking a hard look at the analog inputs would be worth your while.

Most PLCs or PACs (Process Automation Controllers) have a range of available Analog Input cards that range from cheapo single ended 10 bit without even native filtering to isolated 16 (or better) bit high end cards with configurable filtering. Given that many field instruments are 2-wire loop powered, some AI's offer a 24V power from the AI card to power the field instrument.

Again, if accuracy (how the measurements compare to a traceable certified standard) is of concern, then taking a look at how the analog input is calibrated, particularly if it can be. Believe it or not there are some PLCs AIs that can not be field calibrated; any adjustment to the value has be done by jiggering the scaling values. If periodic calibration is a requirement then the process (people, software, procedure, hardware) needed to achieve that is better examined before purchase, than after. That was the case in the fish world, again, whether it matters a ding in the plant world, I don't know.

With regard to connectivity, my personal bar stool opinion is that Siemens reluctantly does Modbus and makes Modbus as obtuse as possible in order to generate support for Profibus/net, which was 'invented' by Siemens, in order to keep their customers corraled inside the Siemens stockyard. Take evaluation as you wish.