from a logistis point, you will not be putting your valves out at the corners, although the final water will reach out that far.
it would be possible to have one row of water and all valves in that center row, with hoses out to the crops.
as was mentioned, if you have soil moisture sampling and such, then you will have sensors out near the far reaches.
If you have solar power, you could have mulitple controllers that are wireless. it seems you have lots and lots of options here.
take some time to sketch out your land, where the main water lines run, as that will be the easiest place to run your power as well. if you sketch it out a few ways, and lay out the typical distances of your wirelss options, and your wired options, the answers may present themselves. if you have a bowling alley or a squre, the layout may dictate your parts selection.
as for POE, you need to allow for the power of the solenids. frequency of operation and method of operation. A motorized valve fails in place. needs power to open, then again to close.
Some solenoids need power to change state each way and use no power while in state. most require power to hold position.
I would offer that if you start with one loop. add in all your sesnors, controller(arduino?) and valve, you can get a feel for the work involved and make a second, use a different set-up and see how that works.
as for control, once you get one up an running, you will find that simple 'keep it wet' is all you need. google spreadsheets and such might be fun for data logging, but not needed for control.