Dale R. Hicks, Department of Agronomy and Plant Genetics, University of Minnesota
The extreme winds that occurred in southern Minnesota on August 3rd caused corn to lodge badly. Lodged plants will likely yield lower and make harvesting more difficult.
Will the corn straighten up?
Some stalk straightening will occur, but plants will not completely stand erect. Most of the straightening will occur within the next 2 to 4 days. After that, the plants will not grow upright anymore. Most of the straightening will occur near or above the ear position. The plant will be goose necked. And, ears on goose necked plants will be closer to the ground and higher-than-normal harvest losses may occur. Slower harvest speeds will help to reduce the harvest losses. Lodged plants (and usually in a twisted mass) also increase combine operator fatigue during harvest.
Effect on Pollination
While most of the corn in the affected area is pollinated, some may not be, especially in low areas that have been wet and slow to shoot tassels. The amount of pollen is not likely to be a limiting factor, but some silks may not catch pollen because they are physically hidden below other silks when the plant and ear are leaning over. This may not reduce the number of kernels per ear substantially, but lower kernel number per ear will reduce the yield potential. The missing kernels will be on the lower side of the ear, facing the ground.
Effect on Yield
Grain yields will be affected because of poor sunlight interception. When plants are leaning, leaves are 'stacked' on top of each other. The top layer of leaves gets good sunlight, but the leaves farther down are shaded and are less efficient in photosynthesis. With normally standing plants, more of the leaves intercept sunlight, or the solar energy penetrates to a lower level in the corn canopy and is captured by more leaves.
Often in field situations, wind lodging results in different degrees of plant leaning. When some of the plants are standing or lodged to a lesser degree than other plants, the leaf canopy is more 'rough' and light can penetrate to lower levels in the canopy. Some plants that are standing more erect will have more of their leaves at light saturation levels, and will increase yields because there is more solar energy to fill grain on those plants. This minimizes the effect on yield, but will not completely compensate for the lower yields of severely lodged plants.
A University of Wisconsin study simulated plant lodging at various growth stages and found that younger plants straightened more with less effect on yield than did plants that lodged at the pollination stage. In that study, plants lodged at the pollination stage yielded 13 to 31% lower. All plants were lodged in that study; the effect on yield should be less if there is differential lodging as compared with all plants lying over.
Lodging is a stress on the corn plant. With reduced photosynthesis, plants will move plant sugars to the ear from stalk storage earlier than normal. As a result, weak stalks occur and stalk rots will invade the lower stalk at an earlier calendar date. Weak stalks that are leaning because of wind lodging may break over sooner, which will also add to the preharvest loss.
Corn plants that are wind lodged will straighten some and will do so in the next few days. Grain yield will be reduced; the reduction will depend on the percentage of plants lodged. Harvest losses could be higher, but minimized with slower combine speeds. Harvesting may take longer and be more stressful (in addition to the personal stress caused by lower yields).