Just out of curiosity what was your seeding rate? This was Spring planted into WR? I had al intentions of adding Sunn Hemp this Spring but rain made it impossible.
(For others as well...)
We have been having issues with Marestail in our RR beans. After a pine thinning and controlled burn it popped up all over the place in the pine. It then got into our fields. Since it is naturally gly resistant, planting RR beans and using gly was just promoting it. So, we started on a program to control it. Last spring I hit it with 24D amine, waited a couple weeks and then planted buckwheat as a smother crop. I was concerned that the soil residual effect may be a problem for the buckwheat, but we must have waited long enough.
This year, I wanted to spend at least one more year controlling it. I've always been intrigued with sunn hemp. It is a legume that fixes a lot of N and can tolerate poor pH and infertile soil. I decided to mix it with buckwheat. I looked around for seeding rates, and the best I could find was 10 lbs/ac of each for a mix. I was concerned that higher rates of buckwheat would smother the sunn hemp. My cover crop last year was WR/CC/PTT. I first sprayed it with 24D for marestail control and then waited a couple weeks. I then surface broadcast 10 lb/ac of Sunn hemp and 10/lbs/ac of WR into the cover crop. Next, I used my little no-till kasco versadrill. I plugged all but one tube and put sunflowers in it. It has a cultipacker to close the rows and I figured this would push the buckwheat and sunn hemp into the soil a bit.
Results:
I got almost no sunflowers. I suspect this was largely due to browse pressure. I got good buckwheat germination, but it was thin. As the plot grew, I could find little buckwheat. This is what keyed me in on the browse pressure issue. Buckwheat germinates quickly and when you don't later find mature buckwheat, you know where it went. It may have taken my deer some time to get used to sunn hemp. Because the field was thin, a lot of grasses and weeds are in the field. This is not necessarily bad since there is still good sunn hemp in the field and many of the broadleaf weeds are good deer food.
In several fields the sunn hemp is browsed heavily. In other fields there are areas where it has grown significantly taller than the weeds. All in all with that planting method, I will increase my rates next year by a factor of 2 or 3.
For comparison, I have some retirement property about 15 miles away. It has been in pasture for many years and the soil is much better. It still has a high clay content but has much more OM. I planted about 25 lbs/ac of each on that field and opened a second tub for sunflowers. It is a much thicker field with both mature buckwheat, sunn hemp, and a fair number of sunflowers. I'll try to remember to a picture next time I'm down. I'm guessing that location has lower deer densities as well. While there are weeds in that field, it is clearly dominated by the crops I planted.
Thanks,
Jack