Considerations in Deciding When to Start Planting

Deciding when to start planting can sometimes be overwhelming if you take into considerations the factors (Figure 1) that have an influence on corn emergence. We need to remember that corn is a warm season crop. Hybrids that are available today have great yield potential and provide the basis for tolerance to cold stress, but poorly planted seed never reaches its potential yield due to the fact the environmental factors can still reduce stand. Many growers resist planting early because the soils are too cool for emergence, however planting as early as possible helps the corn plant maximize its yield potential by utilizing more of the growing season. 

Soil Temperature

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Corn development is related to soil temperature. Good germination and emergence are likely when the soil temperature is a minimum of 50 degrees at a 2-inch soil depth. Corn stands may be reduced when the average soil temperature is below 50° F. If planting before optimal soil temperature has been reached or maintained, seeds may remain dormant in the soil, however, when this occurs they become increasingly vulnerable to diseases and insects. Growers should not only consider soil temperature at planting but also the expected temperature when seeds begin rapidly soaking up water.  Establishing a good stand can be improved greatly with at least 24 hours of warmer, moist soils for germination to occur before a cold stress incident. Choosing hybrids with higher stress emergence scores can help reduce exposure to stand loss due to cold soil temperature. Selecting a hybrid with higher stress emergence is a good practice to follow so check with your local seed advisor to determine the stress ratings for the hybrids that you will plant this spring.    

Soil Moisture

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With spring comes field preparation followed by planting so it is important to know your soil moisture level. Knowing how much soil moisture you have helps in minimizing the impact of fieldwork on soil compaction. Adequate soil moisture is also a key to uniform emergence. Most growers know what adequate soil moisture looks and feels like. In essence, adequate soil moisture is probably close to field capacity. Corn needs to absorb (imbibe) soil water to approximately 30% of its weight and the soil temperature needs to be at about 50°F to germinate. Uneven soil moisture throughout the seed zone is the primary cause of uneven emergence and uneven emergence can easily translate to yield loss.

As you, begin thinking about planting keep these key points in mind: 

• Corn is a warm-season crop
• Choose a hybrid with a higher stress emergence score
• Minimize cold stress:
  • Minimum soil temperature at planting is 50° F
  • By having at least 24 hours of warmer moist soil for germination before a cold stress event
• Factors that influence corn emergence:
  • Environment
  • Genetics
  • Seed Quality

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