Plant by Soil Temperature and Conditions

  • Planting corn or soybeans early may have some benefits, but caution should be taken not to plant fields too soon.  
  • Planting early can help to maximize yield potential, but planting too early may also have a negative impact on yield potential. 
  • Planting should be accomplished according to soil temperature and conditions as opposed to the calendar date.
  • Proper planting depth is also important and can be dependent on many factors and conditions. 

Optimum Temperatures

If spring temperatures tend to be above average, growers may anticipate
an early planting. However, soil must be given time to warm up before seeds are planted. For optimum germination, corn requires a soil temperature of at least 50° F, and soybeans require a soil temperature of 55° F.1,2 Soil temperatures below optimum can cause seeds to sit dormant and become more vulnerable to diseases, insects, and animal predators. 

Imbibitional chilling injury can also take place in corn and soybeans. Seed
imbibition is a two-step process where water is absorbed into the seed and the seed swells. Water intake activates enzymatic processes eventually resulting in germination and emergence. If the imbibed moisture comes from a cold source, such as chilling rain, the cell membrane can become
rigid and rupture. This may result in damaged or aborted radicles, lower germination, and delayed seedling growth affecting nutrient uptake, seedling development, and pest entry. Symptoms of chilling injury, including swollen seed that has not germinated and a fragile or absent primary
root, can also be caused by other factors and may be compounded
by additional stresses during germination.

Corn Planting  

Proper planting depth is critical for good nodal and brace root growth.  The ideal planting depth is dependent upon many factors including geography, soil type, environment, and planting equipment. Remember, most corn planter’s closing wheels are designed for a planting depth of 2 inches.4 

  • Do not plant too shallow. Planting less than 1.25 inches deep can result in rootless corn or root lodging.4 Shallow planting can also increase the risk of injury from some soil-applied herbicides.
  • Do not plant deeper than necessary. When soil moisture is abundant, plant around 1.5 to 2 inches deep. In high residue systems, planting slightly deeper puts seed into a buffered soil environment with more uniform soil temperature and soil moisture which can help to improve emergence.5 If soil is dry, planting at 2.5 to 3 inches into moisture is less risky than planting shallow in anticipation of rain. 

Soybean Planting 

Proper planting depth is important in soybeans for good stand establishment.  This planting depth is dependent upon many factors including geography, soil type, environment, and planting equipment.  

  • Planting depth matters. Recommendations for soybean planting depth range from 1 to 1.75 inches deep and no deeper than 2.5 inches.6 Deep planting provides stable moisture and temperature conditions to the seed. However, planting too deep can burn energy needed later by the plant, and may inhibit emergence in stressful situations, such as soil crusting and compaction.