How cold temperatures affect corn emergence.
Agronomy Bulletin 17 ─ Early Season Cold Stress
In areas of the Corn Belt, frost and variable soil temperatures can place corn under significant stress after planting.
Factors to Consider
- Planting date
- Soil temperature
- Planting depth
- Damaged seedlings
- Know the importance of soil temperature. The time required for radical emergence is directly related to soil temperature. The optimum soil temperature for constant corn growth is 86 F. Corn seedlings have little growth at soil temperatures below 60 F
- Determine appropriate planting depth. Consideration should be given to ample depth for vigorous root development. Planting seeds at a depth of 1½ to 2½ inches ensures seedlings are exposed to appropriate soil temperatures for optimum emergence.
- Watch for cold temperatures right after planting. During the 24 to 72 hours after planting, germinating seeds may suffer from imbibitional chilling. If the seeds imbibe water and the cell tissues are too cold during this time, they can rupture, causing complete germination failure or issues with radicle or coleoptile emergence.
- Understand how cold temperatures impact seedlings. Cold-temperature stress, including frost and variable soil temperatures, affects the growth of young seedlings. Extended periods of soil temperatures 50 F or colder, as well as major fluctuations of 25 F to 30 F, may injure the emerging seedling. Symptoms may include rotted, split or deformed mesocotyls. Check for rot by opening the seedling and looking for dark, watersoaked tissue. A healthy seedling will have a relatively firm, cream-colored growing point.
- Monitor for discoloration of leaves Corn seedlings exposed to early stress, wet conditions, restricted root development and lack of phosphorus can develop a purple hue. Restricted root growth resulting from cold soils can cause a buildup of sugars in the corn leaf, producing anthocyanins, which cause the purple leaf color. Cool and/or compacted soils along with shallow planting also can create the opportunity for purpling in the seedlings’ leaves. After a few days of warm weather, the corn seedling will recover from the purplish color and, in most cases, yield potential is not affected.
To maximize yield potential and avoid replanting, wait until the soil temperature is above 60 F. Be sure to think about current and future weather conditions to avoid freezing young seedlings. Consider planting seeds 1½ to 2½ inches deep to promote vigorous root development and monitor for injury or rotting seeds if temperatures drop below freezing. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.