A stormy spring season with 14 tornadoes confirmed in Indiana on April 20 alone rekindles thoughts of severe storms last season. One of the strongest in 2010 in mid-June brought destruction and damage to some 5,000 acres, primarily in Benton County and surrounding townships.
The damage ranged from waist-high corn completely blown down and broken off to shredded leaves from hail damage. The truth is that many of the latter types of fields recover reasonably well, notes Bob Nielsen, Purdue University corn specialist, talking about the prospects of recovery after the storm last summer.
Fields that were laid flat and/or broken off after the growing point was above the ground have no chance, he acknowledges. But those where leaves were shredded or the stalk was only partially stripped still can produce a decent crop. The keys are the stage of growth and the actual amount of leaf loss. Other factors are how much damage, if any, hailstones caused on the stalks that could lead to entry points for disease later on.
The 2011 Purdue University Corn & Soybean Field Guide contains excellent charts, prepared for insurance adjustors, that help estimate how much yield you can still expect after damage at a certain point of growth. For example, if corn at the seven-leaf stage loses 35% of its leaf area, but the stalk is still intact, there is no yield loss expected!
Many of the fields hit in Benton County last year were at the 10-leaf stage or even larger. At the 10 leaf stage, 50% leaf loss results in an average of 6% loss of yield. So if the field would have made 200 bushels per acre, the new potential would be 188 bushels per acre.
The numbers increase significantly as plants move toward the reproductive stage, and as the amount of defoliation increases. At the 15 leaf stage, nearing but not quite to pollination, at 50% leaf loss, you could expect 15% yield loss. That drops 200 bushels corn to 170 bushels per acre. Still, it's far better than the field first looks like after the storm. That's why consultants often tell farmers with fields damaged by wind or hail to stay out of the field for a few days, then check them. Some recovery should already be underway.
If corn is silked out and 100% of the leaf area is lost, the crop is in trouble. The table estimates yield loss at 97%. There is simply no factory left to produce starch for the ear, and no time to allow for compensation. On the other hand, 70% leaf loss at silking could still produce half a crop, which would be far better than tearing up a crop and replanting in late June in most situations.The pictures accompanying this information depict damage from the Benton County storm in 2010. Note the difference in damage. Close to where the field was flattened, a toolshed was destroyed as well.