Second, irrigating should be done when wind speeds are expected to be low, since severe winds immediately after an irrigation can lodge plants. In fact, a slight amount of water stress during this period might be beneficial by forcing the root system to branch out. Finally, research has demonstrated that if lodging occurs this period or shortly after, the yield reduction is greater than if lodging occurs during any other period. In summary, soybeans do respond to irrigation although less dramatically than corn in many instances. Soybeans have the ability to compensate for moisture stress because they have a longer reproductive period than corn.
Soybeans adjust to moisture levels by altering the number of pods set and the size of each seed.
Once irrigation has been initiated, ceasing any further irrigation may cause more stress on soybeans than if no irrigation had been done at all. Soybeans tend to 'adapt' themselves to a higher water use rate, and stopping subsequent irrigations may cause severe water stress symptoms not apparent in dryland soybeans which have adapted a lower water use rate. If irrigation water is in short supply, it is best to apply that water during the bean enlargement growth stage. Nebraska studies also indicate that soybeans respond more to irrigation when grown in narrow rows than when grown in conventional spaced rows.