Yep,

Just done a search on winter wheat and came up with this article.
A thought just occurred to me that I could plant a crop of something in the container broad casting the seed thickly. Maybe turnips as they sprout and grow quickly to about 3 or 4 inches high. Just work the greens into the soil when transplanting time comes around.

I did read an article not to long ago where serious and knowledgeable container or yard gardeners manage their soil where they do not need to add fertilizers.

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Green manure cover crops for Minnesota

http://www.extension.umn.edu/garden/yard-garden/vegetables/green-manure-cover-crops-for-minnesota/