Choosing corn hybrids and soybean varieties is one of the most important crop management decisions farmers make. Decisions are typically made months before the growing season begins. And more varieties with new traits are added to the market each year.
Where should you look to find reliable yield trial information? How should you interpret yield trials? What should you consider when selecting a hybrid or variety to plant? Mark Licht, Iowa State University Extension cropping systems agronomist, offers the following observations and recommendations.
Where to find information
Iowa has many sources of yield trial results and information. It is highly recommended to study the results from many sources to help you make the most informed decision for your farming operation.
University trials are helpful because they can compare the yield potential of cultivars from multiple brands in a more rigorous plot design, compared to private strip trials. It may be helpful to also look at university trials in neighboring states with similar growing environments.
Consider other public and private strip trials from FFA chapters, the FIRST Seed Tests, local cooperatives and seed companies. These sources may or may not have entries from multiple brands and often are not replicated.
University yield trial sources include:
- Iowa State University / Iowa Crop Improvement Association
- University of Illinois
- University of Nebraska – Lincoln
- University of Minnesota
- University of Missouri
- South Dakota State University
- University of Wisconsin
Farmers are encouraged to conduct their own yield trials of cultivars and brands they are most interested in. Work with local seed dealers to locate a uniform field area to conduct the trial with easy access, and find the best way to determine yield, grain moisture, and possibly test weight and grain composition. Having your own yield trial lets you know how a cultivar performs under your specific management practices.
Interpreting trial information
The objective of selecting a variety to plant is to predict how well it will do the year you plant it. But you do need to look at past performance. The difference here is that selecting a cultivar to plant requires having enough information from many yield trials to be able to predict future performance. To make predictions, use yield trials that have single location results, 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. When choosing which yield trials to use, consider crop rotation, tillage, soil type and drainage that are similar to your fields. These factors interact with yield potential in ways that affect how well the yield trial will predict cultivar performance on your field.
To use yield trial data confidently, do not rely on the yield value itself. Use information like the least significant difference (LSD) value to tell if a cultivar or variety is statistically different than another.
Grouping the results of trials according to where the varieties finish — in the top, second, third or bottom quarter — can be useful when combined across multiple yield trials. For example, a variety that is in the top quarter for every yield trial has consistent performance, whereas a variety that lands in several quarters is not a consistent cultivar with predictive performance.
Characteristics to consider
Looking for high-performing varieties that are consistent across many locations and yield trials will lead to decisions that are predictive for the next growing season. Consider these characteristics:
Yield and yield consistency. High-yield cultivars have the potential to produce high yields every year, while low-yielding cultivars rarely have the potential to be high yielding. Evaluate cultivars yearly for yield potential since they are typically only on the market two or three years. Look for those 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 to minimize risk. 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 the traits being offered for the specific cultivar. Transgenic cultivars have been very successful where insect and herbicide resistance has not become an issue.
Early-season vigor and emergence. These characteristics are important to achieve the desired harvest population. High seedling vigor helps manage risks when cultivars are selected months before planting. Rapid emergence and vigor can minimize disease risk, while uniform emergence is important for high yield potential.
Standability and lodging. Varieties often have ratings to indicate how easy or difficult they 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 in the fall. While some varieties 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 and drying cycles can still increase the potential for pod shattering to occur.
Grain drydown. Typically, grain drydown is considered for corn hybrids. The ability for a corn hybrid to dry down quickly can lead to earlier harvest or lower grain drying costs. Choosing hybrids with high ratings for grain drydown is important for farm operations with little-to-no on-farm drying capacity. 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.