well I hear you on having some cover in a plot, it does seem to help deer come out sooner
one of the reasons I been thinking about trying them hybred soybeans they have now that grow to 6 ft tall, as if I could get them about half of that, I think that would be awespme , but I hear you really need to fence it off to get that height in them.

they do sell I am sure some chemical that will help keep grass out but not hurt the sorghum, I think its 2-4-d, its a widly used chemical in many of todays comercial food crops
see below
just something to think about
as like I said, if you cna keep it some what weed free, come lat Aug, it should be a good place to throw some rape seed and have a new food source just before winter


this is the stuff, just make sure its mixed right, like all chemicals, thats key to them working the right way!
I am like 99% sure it will not hurt round up ready beans too! but double check, know its safe on round up ready corn, so think there the same deal, but not 100 %
2,4-D
2,4-D is a broadleaf killer that has been around under many brand names for many years. It will not kill grasses. Grain sorghum infested with coffeeweed, ragweed, jimsonweed, morning glory or any other broadleaf qualifies for 2,4-D application. Grain sorghum is a little sensitive to 2,4-D, so read the label carefully and do not increase the label rate. Atrazine is a great herbicide for grain sorghum or corn, but is a controlled chemical requiring a private pesticide applicator license. 2,4-D,, is available over the counter with no license required.