Using synthetic NPK (Nitrogen, Phosphorous, and Potassium) fertilizers, one acre of land can produce 200 bushels of maize. The same field, unfertilized, might produce only around 60 bushels – a drop in yield of 70%.
Not only is the crop yield greater using fertilizers, but production is steadier. Synthetic fertilizers essentially force plants to grow on ground that would otherwise be barren. In the old days, farmers would leave a field fallow (i.e., unplanted) and perhaps spread some animal manure to return nutritive organic matter to the soil so the field could be replanted in the next season.
Fertilizers allow farms to circumvent the inefficient process of leaving a firm fallow in the same way that factories allow manufacturers to circumvent the inefficient process of artisans crafting custom-made goods.
While synthetic fertilizers might sound great, the added yield and production regularity comes at a cost that science is just starting to understand.