There is no one-size-fits-all cover crop. Before deciding on a cover crop (or mixture) to seed, you have to decide what function(s) you want your cover crop to serve along with where, when, and how you can seed it. From that starting point, you can then narrow your cover crop choices.
The best resource on cover crops is SARE’s Managing Cover Crops Profitably. You can get a free pdf download of the book. It includes many examples of successful integration of cover crops into different farming systems, as well as charts of important cover crop traits. This book is a must-have for any farmer interested in cover cropping.
Use the interactive “web of cover crop functionality” below to explore some of the ways in which cover crops work (not all boxes have a link as this is a work in progress).
We are myopically soil-focused and this “web” does not include the mostly above-ground effects that cover crops might have on insect populations and dynamics, but it should be noted that cover crops, especially flowering ones, can substantially impact insect dynamics.