Tolerance to Competition: The Next Major Step to Improving Sweet Corn Yield.

In the last century, significant gains in field corn yield have resulted from the combination of improved genetics and superior management practices.  Environmental stress tolerance is considered the physiological trait most strongly linked to genetic improvement, whereby modern hybrids have greater tolerance to a host of biotic and abiotic stresses.  Several researchers have shown that, of all environmental stresses, tolerance to intense competition has improved the most.  As a result, maximizing yield in modern field corn production requires growing improved hybrids at populations that are higher than their predecessors.  Can the same be said of sweet corn?  Recent research has shown that sweet corn hybrids commonly grown for processing in the Midwest vary greatly in tolerance to elevated populations.  For instance, populations that maximized yield ranged from a low of 48,100 per hectare to a high of 70,200 per hectare, depending on the hybrid.  Consistent with field corn, those hybrids performing best under elevated populations yielded the best.  Gross profit margin to the processor varied some $3,300 per hectare among commonly grown hybrids.  Differences in gross profit margin were the result of both green ear mass yield and recovery (i.e. kernel mass as a fraction of ear mass).  These results show stark differences in tolerance to competition among crop plants (i.e. intraspecific), and suggest that not all commercial hybrids have been selected for tolerance to intraspecific competition.  The average population density used by growers is too low to maximize yield of the highest-performing hybrids.  Both growers and processors could realize increased yield and profit by using certain hybrids at populations higher than currently used.  Ongoing research is identifying the latest hybrids that perform strongly in elevated populations and revealing key mechanisms driving this tolerance to competition.