Although I haven’t trialled them yet, I must have come across a report (presently unciteable) which mentioned azuki beans, also known as adzuki beans, as a cover crop option in tropical areas.
According to the Wikipedia azuki bean entry, they seem to be common worldwide, as a foodstuff. Maybe that is why I have them in mind, but I don’t consider them a serious contender as a cover crop spp. Speaking to a grain trader lately, I learned that seed is hardly available here and dear enough ($1500/t). He also warned me they are a thirsty crop and hard to grow even under irrigation. I should have asked him if that was for biomass as well as seed.
I wonder if they are too soft for dry hot summers? The grain size (5mm) reminds me of vetch which is a spp I am not keen to grow, cool or warm season, since any winter growth in our lentil phase of rotation can downgrade samples. Vetch can neither be sprayed out of lentils nor cleaned out of the seed, or at least not easily. If azukis only germinated in spring or summer then we could get away with it, and since they won’t be going to seed, it is only the hardseeds which present the hazard. And that is the issue with any species considered in a cover crop mix, to not let it interfere with the cash crops.
Admittedly azukis are one of those longshot ideas, like the purple king beans, and dwarf beans I tried. And any legume amongst the mix will be displacing cowpeas and lablab as the staple legumes, so they need to be pretty good, even if only to add to genus diversity.
So, should I small-plot trial them anyway?