Question is in reference to corn.  But the question would be applicable to other crops as well. 

Corn reaching maturity is dependent on growing degree units, GDU's.... right?  But what about yield? 

Photosynthesis and/or sunlight I would assume plays more of a role in that than just mere GDU's.   We could have a growing season with little to no sunshine, but have more than adequate GDU's to get the corn crop to maturity.   (This is not likely, but it is possible.)  All other parameters being equal... would the corn crop yield as well as it would in an average year of sunshine?

I think our farm has experienced less cloudy days this year than usual.  But we're also a little behind in GDU's too.  Always in the past I've figured we need above average GDU's during our growing season to have a chance of above average yields.  Being as far north as we are, that's been my strong assumption.  But now I'm wondering what the relationship is between yield and sunlight for photosynthesis too.  It can't be just all about temperature... can it?

Anyone got an opinion on this? 

thanks, gordon