Many people have tried to analyze what the future holds for continued increases in crop yields. After studying time series of average U.S. yields for 19 crops, Lin and Seaver  concluded that 12 crops including corn, cotton, and wheat have reached yield plateau, and the seven remaining crops including hay and soybeans yields have had a slowdown in their rate of growth. On the other hand, after presenting some of the possible new technologies or changes in existing technologies that could boast yields, Wittwer  concluded that it is reasonable to expect possible large increases in yields. Wittwer's list of possible technologies included: changes in the plants' ability to withstand environmental stress; changes in the plants' ability to utilize fertilizer including the possibility of more plants with nitrogen fixation capabilities; increases in the plants' photosynthetic efficiency; and increases in the use of chemical growth regulators. Heady , after reviewing a host of other studies, observed that probably the best that can be hoped for in the future is the continuation of the current absolute increases in yields.
Schatzer, Raymond J.; English, Burton C.; and Heady, Earl O., "Future Crop Prices and Quantities: Influence of Alternative Crop Yields" (1983). CARD Working Papers. 27.