If you want to prove the power of soybeans to recover and rejuvenate themselves, go out on a couple of rows and beat off half the leaves for a short stretch. It may seem tough to do, but do it anyway. Then come back in a couple weeks.
Shaun Casteel, Purdue University Extension soybean specialist, says the canopy will be closed again. He's done that experiment and even removed all the leaves at various stage of growth. The idea is to simulate what happens if soybeans lose leaf canopy due to a hail storm.
Casteel has found that if the hail comes at R1, which is first flowering, or earlier, and the damage is 50%, leaves will grow back and the yield will be very similar to soybeans which weren't hit by hail at all. Some stems may be bruised or plants broken. But if you had more plants than you needed anyway and still have at least 100,000 plants remaining that recover, there should be any if any yield effect.
As soybeans move deeper into the season, hail can cause more potential yield loss. At the R3 stage, Casteel found that soybeans still recover lost foliage quickly, but there is up to 20% yield loss due to interference with the reproductive process.
If soybeans are hit at R5 or after when pods are developing and the damage is extensive, there will be some recovery but there will also be yield loss. At this point, the energy factory that turns sunlight into materials that fill soybean pods with soybean seeds is too damaged to prevent yield loss.
Like Bob Nielsen, Extension corn specialist, Casteel believes it's better to see how beans will recover rather than making snap judgments right after the damage occurs. This is especially true if it occurs soon, while many soybeans will still be in the vegetative to early reproductive phase.
Have hail damage on corn? Check out these tips for estimating yield loss from hail on corn.