What's So Important About a 50-Degree Soil Temp?

Why do we always tell growers to wait to plant until soil temperatures are 50 degrees and the extended forecast looks good (for 24-48 hours)?

Kevin Carlson, Federated's senior agronomist answered this question:

The first 24 to 48 hours after planting corn are extremely important to seedling health and for optimum stand establishment. Corn seed needs to take up roughly 30% of its weight in water prior to germination. Since the corn seed can take up water under that 50-degree mark, the potential problems start: If the soil is cold, the corn kernels take up cold water and begin to swell. If the conditions are too cold, the cell tissues become less elastic and may rupture during the swelling process.

Even if the cell tissue does not burst with the cold water, other chilling injury symptoms can occur including:

  1. stunting or death of the seminal root system,
  2. deformed elongation of the mesocotyl (corkscrew effect),
  3. delayed emergence,
  4. complete failure of emergence,
  5. leafing out underground.

The nearly guaranteed results of cold soil at planting are poor germination and a thin stand count.  Once the soil temp reaches that 50-degree critical level, the above stated problems start to disappear.  

Thus, the million-dollar question: Do you wait? Feel free to discuss the answer with your Federated Agronomist.