I worked for a commodity consulting firm from 1973 to 1976. This was my first job out of university. I learned about the supply and demand for everything from cotton and live cattle to soybeans and zinc.
In my early commodity days I learned that corn grain yield improvement began in the mid-1950s in response to continued improvements in genetic yield potential and stress tolerance plus increased adoption of nitrogen fertilizer, chemical pesticides, agricultural mechanization, and overall improved soil and crop management practices.
Further improvement in yields to feed the world's billions may prove elusive as people reject GMO crops and prefer organic produce with lower yields.
Water for agriculture is a growing problem throughout the world and not just in California.