Keep An Eye on Soil Temperatures

While there are many benefits to planting early, planting too early can have negative impact on yield.  Planting in soils that are too cold or too wet will cause seeds to sit dormant and become more vulnerable to diseases, insects and animal predators.

Let soil temperatures and soil conditions – not the calendar – dictate your planting date. For a map of current soil conditions throughout Iowa, click here. We recommend waiting until soil temperatures in a region reach between 55 and 60 degrees Fahrenheit before you plant soybeans or 50 degrees before you plant corn. Remember, soil temperature for soybean planting is more critical than for corn. The main reason for this is because soybeans can germinate in a soil environment of about 55 degrees Fahrenheit, but if the air temperature after germination hits 28 degrees Fahrenheit or less, the young seedling can be killed with the growing point of the plant right at emergence. Adversely for corn, the growing point stays under the surface until much later.

If planting conditions aren’t fit for planting, yield may be sacrificed due to:

  • Chilling Injury – Imbibitional chilling can negatively affect both corn and soybeans. This happens often when farmers jump the gun and plant in soils that are too cold. For a seed to germinate, it must absorb water, which usually happens within a few hours of planting. If the water is too cold, tissue damage will occur within the seedling and will either kill it or drastically slow down emergence. This can allow diseases and other problems to enter. Typical symptoms of chilling injury may include a swollen seed that has not germinated, as well as a fragile or absent primary root.
  • Soil Compaction – If mud sticks to your tires and ruts are deeper than an inch, the field is too wet to work.  Compaction will likely result, causing decreased germination, root and plant growth, as well as nutrient uptake.
  • Soil Crusting – Wet soil at planting can cause a crusted layer to form, which may delay or prevent seedling emergence.  Soybean hypocotyls can easily break as they push through the crust, which may result in significant stand reductions and lower yield potential.