Given the millions of backyard gardeners who produce yields beyond what the most productive mechanized farms of the early 20th century were capable of this claim is demonstably false. Contrary to the BS you are apparently swallowing with little skepticism from this class, modern varieties are not completely dependent upon heavy loads of fertilizer, etc. What makes them different is that when provided these addditional resources they will thrive and produce a large yield instead of shutting down and they can toldate being overcrowded (as well as having the structure to support the he's ier yield).