By Liz Stahl
What impact have hot and dry conditions had on soybean pests and the soybean crop overall? Drs. Seth Naeve, Extension Soybean Agronomist and Robert (Bob) Koch, Extension Entomologist, joined Dr. Angie Peltier, Extension Educator-Crops to discuss these issues on the August 5th Strategic Farming: Field Notes program.
Hot and dry conditions cut top-end soybean yield
Even though areas of the state have caught some rain recently, good portions of the state are still dry or very dry. When soybeans are under moisture stress, stomata (tiny openings or pores that facilitate gas exchange and evaporative cooling) on the undersides of plant leaves will close.
When stomata close, the plant stops taking in carbon dioxide and releasing oxygen, reducing the capacity of the soybean plant to photosynthesize. This means the soybean plant isn’t able to capture new energy that could be used for vegetative growth, or seed growth, which ultimately results in lost yield potential.
Evaporative cooling, which normally occurs as water leaves the plant surface, is greatly reduced when stomata are closed. As the soybean canopy increases in temperature, soybean plants will start to flip their leaves to reveal the lighter underside. There is a specialized organ (Pulvinus) on the leaves’ petioles that helps a soybean plant flip its leaves in hot, dry conditions. Seeing a field of soybean with flipped leaves indicates the crop is under stress.
Source : umn.edu