It is important that we understand the processes of corn germination. The corn germination process should help dictate how we plant, when we plant, and the conditions we place seed into.
Germination is the process by which a plant grows from a seed. Typically, the factors that affect seed germination are:
- Soil temperature and soil type
- Moisture and oxygen levels in the soil
However, corn has no light requirement for completion of germination; therefore, the two areas of focus are temperature and moisture. The optimum soil temperature for corn germination is 55°F. As soil temperatures increase to above 50°F corn moves towards the process of completing germination but if soil temperatures decrease to below 50°F those processes stop. Typically soil temperatures that remain at or above 55°F for 5 consecutive days after planting offer the most ideal conditions for germination. A corn kernel must also absorb (imbibe) 30% of its weight in water before germination can begin. Rapid drying of the seed zone after initial absorption may slow or stop germination. Repeated rapid wetting and drying cycles can decrease seed viability and lead to less than ideal stands.
Figure 1 provides an illustration of seedling corn emergence. After the imbibition of water, under adequate temperatures, the radical root emerges first near the tip of the corn kernel.
The coleoptile then emerges next from the embryo side of the kernel. This happens within one to several days after the emergence of the radical depending on soil temperature conditions.
The coleoptile is often called the spike and will split open as it nears the soil surface as the plumule leaves inside begin to emerge.
The last visual step of germination is the lateral seminal (seed) roots emerge and begin to elongate. These roots are not necessarily a part of the permanent, nodal root system. The first true nodal roots will begin when the corn plant reaches V1.
All the germination processes rely on the energy stored in the seed until emergence when the first true leaves emerge and the plant switches and relies on photosynthesis to conduct growth and development. Corn typically takes 115 to 120 Growing Degree Days (GDD) after planting to emerge.
Summary and Key Takeaways
- Understanding the process of germination can help aid us to make key planting decisions to optimize corn stands. A few things to consider are:
- Understand what current soil temperatures are and what forecasted temperatures appear to be to ensure you have adequate soil temperatures at and immediately after planting.
- Understand how drying and/or wetting affects the germination process and use proper planting depths and practices to place the seed into adequate moisture.
- Understand that after the germination process starts the same environmental factors (moisture and temperatures) can slow or stop the processes which can greatly affect the viability of the seed.
Nielsen, R.L. (Bob). 2019. The visual indicators of emergence in corn. Corny News Network. Purdue University. https://www.agry.purdue.edu/.
Elmore, R. and Mueller, N. 2015. Corn and soybean survival in saturated and flooded soils. CROPWATCH. University of Nebraska-Lincoln. https://cropwatch.unl.edu/.
Web sites verified 2/22/2021.
Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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