I am in a tropical climate (12.8° N of the equator; 600m elevation). I am looking at cover crops that I can use, particularly those that will add biomass and nitrogen to my rocky clay soil.
Sunn Hemp (Crotalaria juncea) seems like a good candidate. Does anyone here have experience with it?
I also have what probably will seem like a weird question. How much does it look like marijuana? I ask because I live in Nicaragua and our President is very anti-drug. We also have a bunch of nosey neighbors around us. I am a resident here, not a citizen. The absolute last thing that I need is for one of my neighbors to see Sunn Hemp on my property, mistake it for marijuana, and report it to the police. Logic likely will not prevail with the police, especially if there is a resemblance to marijuana. I could potentially find myself in jail for an indeterminate amount of time and subsequently deported.
If this plant does indeed have a resemblance to marijuana, could anyone suggest alternative cover crops that I might try. Most of the available information applies to temperate climates in North America and Europe. I am not sure how the recommended plants will work in my area.
Dave Brandt reports it is a tremendous nitrogen fixer that grows nodules the size of baseballs. He also got a visit from local police in Ohio regarding his cover crop. My understanding is that he found it an excellent cover crop, fixing lots of nitrogen and producing tons of biomass.
We use sun hemp extensively on our farm. First of all, we eat it. The leaves are used as a green leafy vegetable. Not my favorite, but not bad once in awhile. Second of all, its a great nitro fixing cover crop, and it grows anywhere. The soil here was absolutely horrible (acidic clay) when I started 5 years ago, but the sun hemp grew, and I think it did a lot to help build my soil to what it is today. (Which is still not great, but its improving with every year.) I put it under my bananas and basically anywhere else there is bare soil with no plan. It does NOT look like marijuana at all. It makes beautiful flowers (which are also edible), and then big fat pods about the size of a thumb that turn black when they are ready to harvest for seed (and they rattle.). How big it grows depends on the soil. In crap soil the plants will be small, and the leaves will be small and narrow. As the soil improves, the leaves get bigger, longer and fatter, and the plants get taller. But they still don't resemble marijuana, even when they are very happy. I have some still in the ground if someone wants to see a picture, and an example of how it looks when its grown in poor dirt. Just planted a new batch down in the wetlands (aka the toilet bowl) for the dry season, but it hasn't germinated yet.
I tried Sunn Hemp a few years ago, with inoculant. I found that it did not do well for me (zone 6 CT) and it did not out compete the local weeds even at the height of summer when temperatures are hot. I reverted to using other types of cover crops or green manures. For my money, piper sudan grass or sorghum is a better choice. I planted just over an acre of it in a fallow field at 50 lbs to acre and mowed it once in the middle of summer when it was a couple of feet tall with a drum mower. I let it alone and regrow (too busy to get back to mow again though I could have) and when I mowed it over a week ago, the plants were at least 10 feet tall in places.
The nice thing about this grass is that it winter kills and will begin to rot down prior to plow down next spring.
You might want to watch this short video discussing sun hemp as a cover crop. The folks at Green Cover Seed are experts in the cover-crop approach and have published many videos discussing dozens of different plant choices for cover crops and the advantages and disadvantages of each.