Land is not a constraint in many places, definitely not in the US. Something like half the corn harvest is already used for solar energy in the form of ethanol. PV produces 20x the useful energy that corn for ethanol does, converting that land to PV would produce 3x the electricity we currently consume. On top of that there's other bio-energy crops like soy bean oil, or land that shouldn't be used for farming at all due to unsustainable water practices.