>Vegetable farms and solar farms both need lots of sunlight and open space. But how do we divide our limited lands between these two priorities?
We are in no way limited by farmland space. Farmland utilization has been dropping since WWI thanks to the invention of artificial fertilizer, and even without artificial fertilizer at current population levels we would have never ran out of farmland although there would be a lot more of it. All across the midwest you will find tracks of land that use to be farmland, but is now either overgrown with trees, grass, or shrubs and completely unutilized for any human purposes. And our main limitation to growing even more food if we wanted a bunch extra for some reason would be fertilizer production/energy, not land space.
This is great science and knowledge, but I don't expect anything useful coming from it for farming on earth. There is no shortage of dirt that the sun shines on now or anytime soon, and no matter how efficient your panels, plants, or extra lights are, the sun is free and a greenhouse is way cheaper than anything else you could possibly build.
Meanwhile, when planning and streamlining infrastructure for cities and large urban centres some do look to guidelines such as minimising transportation (food into cities, refuse out, etc) and transmission line costs.
Food production has water, sunlight, fertiliser etc. requirements, energy generation (solar, wind, coal, oil, gas) similarly has geolocation (sunlight for solar, temperature differentials for wind, mine / port access for solid fuels, pipelines and tanks for gas) requirements.
Urban planners also look to stability of supplies and robustness of systems (if X fails, what do we fall back on).
These are the manner of things that can put dual use demands on various parts of the ring about large urban areas.