[lambdadmitry]

The most important fertilizer is some form of ammonia (bioavailable nitrogen) and you can't "run out" of nitrogen really, not on this planet. Energy requirements of fixing nitrogen are high, but the process is quite robust to fluctuating power supply, so you can easily use "green" energy to do this. So in the end you either let bacteria do this (e.g. in legumes' root nodules with questionable energy efficiency) or you do this on industrial scale, using solar energy to efficiently fix nitrogen and introducing it manually to the soil. It should not be a question of "what's natural" or what feels better, rather it's a question of energy efficiency and reasoning from first principles.