I've been noticing little snippets of cover-crop observations lately, none of which is quite enough to make its own post.  But maybe you won't mind a hodge podge.

The photo above shows how the yellow jackets are swarming around unopened fava-bean buds.  I assume they're stealing nectar somehow, a bit like the ants I noticed on okra flowers a few years ago.  Presumably unrelated to the yellow jackets, our fava beans have been blooming for weeks, but keep dropping the ovaries without setting fruit, so they might not be a good edible in our location after all.

Then there's the observation two of you made in comments, that the puny fava beans between my sunflowers are due to allelopathy.  I hadn't realized that sunflowers were allelopathic, but the internet suggests that is indeed the case, and that water dripping off sunflower leaves can carry chemicals that make surrounding plants do poorly.  I guess sunflowers aren't the best candidate for multi-species cover-cropping campaigns!

My last observation is four-footed.  Goats love oat leaves so much that I've been earmarking a large proportion of that cover crop for goat treats.  I can't help it!  I know the soil loves oat biomass too, but when Artemesia blats at me, I give in and provide any treat I can think of.  In case you're curious, my ability to spoil animals is nearly unparalleled....