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Considerations for Cool Planting Seasons


High-yielding corn demands stand consistency. Without consistent stands, corn plants often act as weeds to one another. With forecasted soil temperatures in the 40s and lower 50s for much of Iowa for the upcoming week, the prospect of successful germination becomes even more challenging.

Practicing patience and waiting until soil temperatures are 50 degrees and warming prior to planting corn is always recommended. Per Iowa State, corn yields are not generally negatively impacted by planting date until after mid-May. However, as the calendar progresses, some growers may be tempted to plant into sub-optimal conditions. Understanding the germination process, the associated risks with planting into less-than-ideal environments, and potential strategies to counter some of those risks need to be considered.

  1. Seed absorbs water and starts producing Gibberellic Acid.
  2. Gibberellic  Acid  creates  A-Amylase, which  converts  stored  starches  into  usable sugars. Phosphorus is utilized as the backbone of energy transport in the developing seedling.
  3. Zinc moves those usable sugars from the Endosperm to the developing Embryo.
  4. Auxin and Cytokinin are produced and increase cell elongation, division, and growth.


These 4 Steps to Germination are largely driven by soil temperature. With cool soils these processes take place very slowly—or not at all. When exposed to cold soils and soil moisture during the initial water absorption stage (first 24-48 hours after planting) seedlings can be injured and even suffer deformity and death from Imbibitional Chilling. Fields planted too wet can lead to smeared sidewalls, resulting in restricted season-long root growth.


Management Decisions:

While not eliminating all early season planting risks (such as Imbibitional Chilling or Sidewall Compaction), there are several management decisions growers should consider if choosing to plant into cool soils.

*Note: while 50 degrees is discussed as the threshold for “cool” soil temp, optimal growing conditions for corn are not reached until 86 degrees—meaning these management decisions continue to reduce stress, aid in seedling development, and provide benefit well into the traditional Iowa planting season.


Supply  the  Seedling  with  Early-Season  Nutrients:

Phosphorus and Zinc are critical to successful germination and early-season vigor. Cool soils limit the availability of soil Phosphorus (Figure 1) and early-season zinc uptake is often low. Supplying a balanced starter fertilizer that includes Phosphorus and Zinc supplies these nutrients near the seedling, providing them with easy access to the nutrients they need for a strong, healthy start.



Add  the  Right  Plant  Growth  Regulator: 

The  process  of germination and growth is dependent on naturally occurring Plant Growth Regulators (Gibberellic Acid, Auxin, and Cytokinin). Using an optimized PGR product like Ascend² along with starter fertilizer ensures that these PGRs are in sufficient supply–and in the correct ratios– to drive faster, more consistent germination and emergence.



Consider Genetics:

Not all hybrids are created equal when it comes to emergence scores and early- season vigor. Make sure growers review early-season germination and emergence scores prior to planting into cooler-than-desired soils. This guide will provide you with some of the emergence ratings for various hybrids


No Starter Equipment?

While starter fertilizer and in-furrow applications of PGRs are effective, not all planters have the capability to use them. The market,  however,  has  recently  seen  several promising seed-applied or “planter box treatment” products (example, Seed+ Graphite) that can help combat early-season stress. These products are often promoted as talc/graphite replacements that feature bio-stimulants and trace nutrients to help seedlings overcome early-season stresses.

Bottom line:

The decisions we make and the management we employ at planting can have real impact on our seedling strength and plant stands, and ultimately play a significant role in setting the direction for the remainder of the growing season.

Contact your CFE Agronomist this growing season.


Content provided by Winfield Solutions, LLC.

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