Seed in planter

Editor’s note: The following was written by Mark Licht, Iowa State University Extension cropping systems specialist, for the university’s Integrated Crop Management News website Nov. 25.


Choosing corn hybrids and soybean varieties is one of the most important crop management decisions to be made. It is a hard decision to make because it is typically made months before the growing season begins.

The objective of cultivar selection is to predict how well it will do next year, not evaluate past performance. The difference here is that selecting a cultivar requires having enough information from many yield trials to be able to predict future performance.

To make predictive decisions, use yield trials that have single location as well as multi-location averages. Multi-location averages are required because they can account for a range of environmental conditions such as weather, nutrients, insects and diseases. Consider crop rotation, tillage, soil type and drainage that are similar to your fields.

To use yield trial data confidently, do not rely on the yield value itself. Use information like least significant difference (LSD) to tell if a cultivar is statistically different than another. Across multiple yield trials, a cultivar that is in the top quartile for every trial has consistent performance, whereas a cultivar that lands in several quartiles is not consistent with predictive performance.

Characteristics to consider

Yield and yield consistency: High-yield cultivars have the potential to have high yields every year while low-yielding cultivars rarely have the potential to be high yielding.

Evaluate cultivars yearly for yield potential since cultivars are typically only on the market 2 or 3 years. Look for cultivars that consistently have high performance from location to location and year to year.

Disease tolerance: Knowing what diseases are common for your area is a key to choosing cultivars that have disease tolerance. Disease tolerance is especially important for diseases that don’t have other viable control options such as Goss’s wilt on corn or white mold on soybean.

Another consideration is how likely you are to apply a fungicide. If a fungicide is not a likely option, look for cultivar disease packages with above average disease ratings.

Transgenic traits: This option can provide insect protection as well as herbicide resistance. When deciding on transgenic traits consider whether you need all of the traits being offered for the specific cultivar.

Early season vigor and emergence: Rapid emergence and vigor can minimize disease risk while uniform emergence is important for high yield potential.

Standability and lodging: Cultivars often have ratings to indicate how easy a cultivar will be to harvest. This characteristic may be key for fields that are typically wet in the fall or are harvested later in the field order. While some cultivars have better standability than others, weather also greatly influences how well plants will stand after maturity.

Greensnap (corn hybrids): Weather events, landscape position and plant development stage are factors that influence the occurrence of greensnap. Cultivar selection can reduce the severity or occurrence of greensnap. Avoiding hybrids that are more susceptible is recommended if greensnap is a common occurrence.

Pod shatter (soybean varieties): When harvest delays occur, pod shatter becomes more problematic. Pod shatter can be minimized through variety selection; however, soybean pod wetting/drying cycles can still increase the potential for pod shattering to occur.

Grain drydown: Typically grain drydown is considered for corn hybrid. The ability for a cultivar to dry down quickly can lead to earlier harvest and/or lower grain drying costs. Using grain drydown ratings can reduce the need for planting an earlier maturity cultivar and potentially losing yield potential.

Seed costs: Prices have been steadily increasing as seed technology and genetics have improved. Balancing the cost of seed with the yield potential can be tricky. Seed discounts should be considered, but don’t compromise on cultivar selection to obtain a discount on seed costs.

Limiting the transgenic traits in the seed can reduce costs, but consider the cost for alternative management strategies in the absence of the trait.

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