Submitted to: Soybean Research World Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 7, 1999
Publication Date: N/A
Technical Abstract: In 1969, I established a maximum yield field at Urbana, Illinois. It quickly became obvious that most years, even in the humid Midwest, water is the major yield limiting factor if the yield goal is >4700 kg/ha (70 bu/a). Thus irrigation is the first requirement for a maximum yield experiment. Without irrigation, yields will be lower and inconsistent from year to year. At low yield levels lodging is not a yield limiting factor and the yield response to narrowing the row spacing is much less. In 1982, using a solid-seeded-semidwarf (SSS) production system, 100 bu/a yields were obtained in Wooster, OH. In absence irrigation, the SSS system has averaged 24% higher yield than the conventional production system of 75 cm rows and taller varieties. The value of maximum yield research is that it permits the identification of yield limiting factors that may be masked by other yield limiting factors in traditional experiments conducted at lower yield levels. A new yield barrier, discovered in 1998, will be discussed that has the potential for having an impact on future soybean yields similar to the discovery of the lodging barrier in 1967.