Is your corn still standing? Tens of thousands of acres were flattened early Monday morning when 100 mile per hour straight line winds blew from Central Iowa across to Northern Illinois and Southern Wisconsin. Corn that was ready to tassel is now knee high and struggling to get off the ground and into the sunlight to finish its work for the year. The crop loss data will be slow in coming out, and could filter into the weekly Crop Progress and Condition Report, but some will not be identified until USDA wades into fields to measure yields for the August Crop Report. What is going to happen to all of that corn?
In the prior Farmgateblog posting Iowa corn was listed more than 80percent good to excellent with adequate moisture and only 4 percent tasseling despite timely planting. Iowa State crop specialist Roger Elmore expects most of the crop to move into the tasseling stage this week, including that which may be more horizontal than vertical. The soil moisture report for the past week in Iowa indicated over 80 percent was adequate to surplus, and Elmore says the damper soils probably allowed more corn to bend downward, and less to break in the form of greensnap. (Small miracle.)
Iowa State agronomist Mark Licht reported, “Wind damage to corn started north of Woodward and moved east through Slater, Huxley, State Center, Marshalltown and eastward. I’ve heard reports that the damage was 8 miles wide in several areas. From what I’ve seen at this early stage is mostly lodged corn to within a foot of the ground and some slight green snap.” And he adds, “The rule of thumb that I follow is that more than 10 days from tassel, lodged corn will ‘goose neck’ to form reasonable rows. Ten days prior to tasseling the amount of corn that will gain vertical orientation again decreases. And after tasseling very little lodged corn will regain vertical orientation.”
The technical explanation for the 100+ mile per hour winds is offered by meteorologist Justin Gehrts of KCRG television at Cedar Rapids, and says the last such winds that blew through the area were in 1993.
On the topic of crop damage, Elmore says it could take several forms, root lodging, greensnap, and pinching.
1) Root lodging occurs when roots on the windward side are pulled up, and when roots on the leeward side are caused to buckle and can no longer support the downward pressure if the plant is twisting in the wind. Elmore says prior to the tasseling stage, plants have more ability to resume a vertical position, but once ears start to fill out, that ability is lost, and goosenecked tops are about all that happens. Elmore says Wisconsin agronomists intentionally lodged corn in the silking stage and recorded yield reduction of 12percent to 31 percent.
2) Greensnap is the probable result of wind when corn is growing rapidly, and the stalk breaks at some point. Elmore says, “We’ve learned from previous greensnap events in Iowa and Nebraska that yield loss is directly related to the amount of stalk breakage that occurred. In other words, yield loss from broken plants is directly related to stand loss. If 10 percent of plants are broken this will result in a 10 percent yield reduction.” But Elmore says more recent research has shown that a broken stalk may result in an ear loss only 50 percent to 73 percent of the time.
3) Pinching is the other potential problem, in which the stalk does not break or bend, but folds. They remain alive and will create a gooseneck, with yield losses somewhere between lodging and greensnap.