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Those numbers I pulled from an agPHD app.
The USDA has a web-based system that you can use (I never have): click here. The numbers that I get, for Ontario, are slightly different (but I can't find the damn webpage that I normally use as reference!).
Page 8 is where the pdf gets interesting/relevant, with a chart of crop averages on pg.10.
I tried to do a quick search for Kansas numbers, but I'd assume you would know best where to look (extension-wise)