-- I'd never heard of the theory that high soil N causes iron chlorosis in soybeans.  (where did you hear or read this?)  My understanding was that the cover crops could reduce iron chlorosis mainly by drying the soil, which isn't surprising since wetness greatly flares iron chlorosis. 

btw, I've seen some horrendous iron chlorosis in soybeans that were planted directly into a wheat cover crop, with the cc being sprayed out *after* planting, so the soil should've been nicely dried out in the top couple feet.  I'm strongly convinced of the value of cover crops for many soil and cash crop benefits, but apparently their ability to reduce iron chlorosis is fairly limited.  (Hint: you can accomplish a lot more with careful choice of genetics to tolerate iron chlorosis.)

(Edited to fix a problem with the fonts and missing 'End Quote')