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. This article will explore where to find yield trial information, how to interpret yield trials, and what to consider in selecting cultivars.
Where to find yield trial information
Within Iowa there are many sources of yield trials. It is highly recommended to combine results from many sources to help make the most informed decision. 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 valuable to look at university trials in neighboring states with similar growing environments. Consider other public and private strip trials from FFA clubs, FIRST Seed Tests, cooperatives, and seed companies. These sources may or may not have entries from multiple brands and often are not replicated.
University yield trial sources:
- 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
It is encouraged for farmers 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 determine 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 yield trial information
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.
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 least significant difference (LSD) to tell if a cultivar is statistically different than another. Even using simple quartiles can be useful when combined across multiple yield trials.
For example, a cultivar that is in the top quartile for every yield trial has consistent performance whereas a cultivar that lands in several quartiles is not a consistent cultivar with predictive performance. Looking for high performing cultivars that perform consistently across many locations and yield trials will lead to making cultivar selection decision that are predictive for the next growing season.
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 to minimize disease 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 of 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 extremely important to achieving the harvest population that is desired. High seedling vigor rating helps manage risks when cultivars are selected months before planting and the knowledge of what weather conditions will be. 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 well 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 drydown quickly can lead to earlier harvest and/or lower grain drying costs. Choosing culitvars with high ratings for grain drydown is most 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.
- Yield trials from multiple sources should be used for selecting cultivars in similar growing environments.
- Use multi-year, multi-location yield trial information that matches your environment (crop rotation, tillage system, soil and drainage).
- Know the source of your data to best understand how to interpret its ability to predict performance for your situation.