I drive along a cornfield every morning where the road goes up a small but lengthy rise. The ground there is somewhat eroded with less moisture holding capacity. Within the past 10 days, lower leaves on those higher areas have fired and turned brown. Ears are drooping. The plants appear to be drying down, even though the field was planted about June 1. The two ends of the field where soils hold more moisture are still green.
Why are those ears dropping? Is it affecting yield? Bob Nielsen, Purdue University Extension corn specialist, says that ears that droop and fall over before the corn reaches physiological maturity, or black layer, are often under severed drought well into the grain fill period. That's likely the case here. My Rain Scout for my house, one half-mile form the field, shows just under an inch of rain total at my location during the entire month of August. My Rain Scout is a service that estimates rainfall using weather information and a patented calculation formula.
Black layer usually occurs soon after the ears droop over, Nielsen notes. Cannibalization of the stalk may be involved, but it may just be that the ear shank loses turgidity or strength and allows the ear to fall over.
Ears affected in this manner will likely yield less. Grain fill will be either greatly restricted or totally shut down. The products of photosynthesis can no longer be transported through the ear shank and into the kernels on the ears. When the shutdown occurs determines how much loss you will see on that individual ear. Obviously, the earlier it occurs, the higher the potential percent of loss.
If the milk line is halfway down the kernel, estimates are that the droopy ear may produce 12% less yield compared to normal ears. The next big question is what percent of plants in the field are affected by this droopy ear phenomenon. The more ears that are affected, the more the impact on yield per acre. If it's just spots within a field, the overall impact will be less.
For example, if 10% of the ears in a field are drooping and have shut down grain fill prematurely, and the yield loss per each of those ears is 12%, then yield loss over the entire field is 1.2%. On 140 bushel per acre corn, that's a loss of 1.7 bushels per acre. At $7 per bushel corn, it's a loss of $11.90.While that's significant, it's not as detrimental as the condition might first appear to be. However, note that in this example only 10% of the ears were affected. And this example does not account for stalk rots that might be more likely to set in on plants that mature before they should, nor potential losses form that disease.