How might soybean yield be affected by hail damage?
In the early morning hours on Wednesday, June 22 a severe storm moved through western Illinois affecting crops throughout much of Henderson, Warren and Mercer Counties, including those at the University of Illinois’ Northwestern Illinois Agricultural Research and Demonstration Center in Monmouth. Preliminary data collected by instruments maintained by the Illinois Climate Network at the center had the wind gusting to 78.1 mph and more than 1 inch of rain falling in a 10 minute period contributing to the nightly total of 3.34 inches. The National Weather Service models showed that ¾ inch diameter hail fell over the area as well. Corn plants were blown over and both corn and soybean plants were damaged by hail.
Soybeans in a planting date trial were at different stages of growth and development when the hail damage occurred; soybeans planted on April 18, May 7, May 19, and June 7 are at R2 (flowers at the upper nodes), V6, V5-6, and V1, respectively.
While plant damage occurred regardless of growth stage, the damage appeared to be most severe on the latest-planted soybeans, with stems of some plants broken over and many of the primary growing points severely damaged (Photos).
While hail damage on soybean can be shocking, the growth habit of soybean and the timing of the recent damage provide encouragement that plants will recover well. Soybeans we grow have an indeterminate growth habit, meaning that they continue to add new leaves for some weeks after flowers have begun to appear. Even early-plated soybeans have only 15 or 20% of their final leaf area now, so most leaf area is still to come. Damage to existing leaf area is thus a relatively minor problem, providing that plants remain alive and capable of forming leaves and pods. Those leaves that remain will contribute to the growth of new leaves. Leaf loss does set back plant development, similar to having planted at a later date, but the soybean canopy typically doesn’t finish developing for another 6 weeks. New leaf area should be starting to appear soon, and a few weeks from now it may be difficult to see any lingering effects of leaf loss.
A full canopy is required for a soybean crop to fully intercept sunlight to produce sugars, fill pods and maximize yield. Those fields in which hail damage lowers stand to fewer than 100,000 plants per acre or so may not be able to develop a full canopy to intercept all of the sunlight that they need to produce higher yields. Provided that the primary growing point of most plants remains unaffected, populations are unlikely to suffer. Most plants that had experienced hail are damaged but not killed, but after flowering, plants with most of their leaf area missing may not recover fully. Fortunately, a full stand of healthy soybean plants can produce more leaf area than they might need for full yields, so some leaf loss now should have minimal effect on yield potential.
It’s been warm enough that flowering in early-planted soybeans began before the longest day of the year this year. While yield loss due to hail damage starts to accelerate as plants pass flowering and enter podsetting stages, we do not believe there is much irretrievable yield loss yet, as long as plants are able to get enough water and the canopy stays healthy.
-Angie Peltier and Emerson Nafziger