As corn planting gets underway for the 2018 growing season, it is important to review and understand what goes into corn the germination and emergence process. Uniform corn emergence is one of the most important aspects of stand establishment and producing high yielding corn. Understanding germination, emergence, and how environmental factors influence these processes is the first step toward ensure uniform emergence.
Germination begins in a corn seed when it has imbibed 30% of its weight in water. While corn can germinate when soil temperatures are 50 degrees F or higher, research has determined that the optimal temperature is 86 degrees F. Visual signs that corn germination is taking place are the appearance of the radicle root, coleoptile, and seminal roots. When temperatures are cooler, the germination process is slower and seedlings are more susceptible to disease, insects, and other damaging factors.
Uniform emergence is one of the most important yield-influencing factors that growers should work to achieve. Delayed emergence can ultimately result in diminished yield. Emergence occurs when the coleoptile “emerges” from beneath the soil surface. The amount of time required for corn seedling emergence will vary based on environmental factors such as temperature and moisture, however it typically requires around 120 Growing Degree Days for the coleoptile to break through the soil surface.
Environmental Factors Influencing Germination and Emergence
• Temperature: For both germination and emergence, soil temperature plays a significant role. Both processes are slower with cooler temperatures. In cases where extreme cold temps exist, damage can be done to the seedling.
• Moisture: Adequate moisture must be present for germination and emergence to occur. Too much moisture can result in damage to seedlings and can promote disease as well. A very critical time period for the corn seed is 24 to 48 hours after planting. During this time the seed is susceptible to imbibing injury if it absorbs cold water. A cold rain right after planting can cause significant damage to the seed.
• Soil Conditions: Several emergence-related issues can result due to poor soil conditions. Compaction, cloddy soil, and soil crusting can all cause problems for seedlings try to emergence.
• Herbicide Injury: Cooler wet weather can increase the likelihood of herbicide damage to slow-growing seedlings.
When trouble-shooting emergence issues this spring, growers should keep in mind that many factors determine the success of germination/emergence of corn seedlings. Knowing what conditions are needed for quick germination and growth will help growers decide when to head to the field with their planters.