Corn folllowing corn yield hit?

Once again there have been reports that corn following corn has underperformed this year.  One of the shortcomings of growing more corn than soybeans is disease pressure.  Another is insect pressure.  It seemed that dry weather kept diseases to a minimum, but not rotating certainly adds to the risk.     Another issue could be nutrient cycling.  Decomposing crop residue could be an issue.  The carbon in the residue ties up the nitrogen in the soil.   Keep in mind that the residue on the top is probably not a big issue, but roots and buried stalks do need nitrogen to start that decomposition process.  Drainage is generally an issue in corn after corn.  That issues is unlikely this year, but we did have good moisture in March and April at least in my area. 

Long term research on continuous corn and corn on corn rotations usually indicate something like  a 10% yield hit.  I have heard lots of people say they do not have that problem, but 6 years in a row with even performance and then a year with a 60 or 70 bushel hit would certainly set your average back at any yield  level.  Does this mean you should not grow long term corn.  Certainly you should consider the consequences.  We have one customer who has grown corn continuously since 1954.  Am I going to tell him to switch off?  I don't think so.  I look at what he is doing. He maintains high soil test levels.  He has well tiled fields.  I bet he watches which hybrids work best in continuous corn.  You also need to take preventative measures for disease and insect repression.  If you decide to go for it, do so with realistic expectations.  If you can't stand the risk, then switch to a corn soybean rotation.