Recent storms brought hail to several areas of Minnesota. Farmers in these areas are working closely with hail and crop insurance adjustors to evaluate damage.
Crop size and condition are quite variable across the area. For corn, one of the most important steps in evaluating hail damage is to determine whether stalks are broken above or below the growing point inside the stalk. At the V7 stage, the growing point is located about 1-2 inches above the soil surface. V7 means there are 7 leaves on the stalk including the initial seed leaf that might be difficult to find by this time. The growing point will look like an arrowhead in the cross section of a stalk split lengthwise. After a few days following hail, the growing point should look firm rather than showing decay. There may be signs of new growth emerging. Corn that is nearly waist high and broken off at ground level will have lost the growing point. New growth may not be able to emerge from some crushed over stalks.
Stalk loss and leaf loss are used to estimate yield loss and crop potential. State Extension corn agronomist Jeff Coulter writes that 16,000 remaining plants per acre can still yield about 76% of the normal yields expected. Corn with 80% leaf loss at the seven to eight leaf collar stage might have a yield reduction of 10%.
Soybean stems that are broken below the growth buds located at the first cotyledon seed leaves will not grow. State Extension soybean agronomist Seth Nave writes that leaf loss through the time the plant has four fully developed trifoliate leaves has little effect on yield. Each leaf attachment on the stem has buds that can be the source of new growth. New growth is usually evident within a few days after hail damage. Recovering plant stands at 80,000 per acre can still yield 90% of normally expected yields. Plant population at 39,000 could still produce 75% of normal yields, depending on growing conditions through the summer.
Wide gaps in plant losses for corn or soybeans will result in greater yield loss.
Where the corn crop is lost, forage sorghum might be a crop option to provide roughage feed. Farmers should understand their insurance coverage clearly in making decisions. Cover crops can be used to capture nitrogen that was applied or to control erosion where a crop was destroyed.
Links to more detailed articles about evaluating corn and soybean hail damage can be found by doing an internet search for "Minnesota Crop News Assessing Hail Damage." In many counties, including Stearns, Benton and Morrison, you're welcome to call the County Extension Office for access to this and other information that might be useful to you.
-By Dan Martens, University of Minnesota Extension