Soybean Variety Selection

SCN-susceptible (left) and SCN-resistant (right) varieties tested side by side in a field infested with SCN.

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Soybean variety selection is one of the most important decisions a producer makes each year. It is the foundation of your crop management plan.

The variety you choose will determine the yield potential, the pest resistance, maturity, and grain quality of your crop, so spending time and effort on selecting the right variety for your specific conditions is a good investment.

 

Choose varieties based on field history

So what variety is best to plant? Overall, the emphasis should be on yield and yield stability. Choose a maturity group that is appropriate for your area and production system. The higher the maturity group number, the longer the vegetative and reproductive stages of development. Refer to your recorded information about your fields, and consider specific characteristics of varieties based on the history of pests, diseases, plant growth, and soil conditions in each field. Compared with the options just a few years ago, there are now high-yielding varieties with better pathogen and pest resistance and improved specialty traits to choose from.

Prioritizing variety characteristics

Soybean variety selection hierarchy.

Figure 1 illustrates how yield and yield stability are the most important varietal characteristics to consider. The next ones, in order of priority, are disease resistance, maturity group, grain quality, and height/lodging characteristics.

• Yield and yield stability means the ability of that variety to yield consistently well. Since it is highly unlikely that next season’s conditions will be the same as those in any single-location test, your best bet is to select a variety that can perform well in many environments. These varieties can be found in reports that display test averages over locations and years. Data from several locations and sometimes years of testing should be available from seed companies. Another important source is the replicated, independent yield trials conducted by all state agricultural universities. Read below about how to use yield data to select varieties.
• Planting varieties with disease resistance is the most effective and economical method of disease control. Many varieties have good resistance or tolerance to most of the major diseases that occur in the North Central region, such as soybean cyst nematode (SCN), sudden death syndrome (SDS), brown stem rot (BSR), iron deficiency chlorosis (IDC), and Phytophthora. Be sure to know what source of SCN resistance you are buying to prevent build-up of a resistant nematode population.
• Soybean maturity group describes the time from flowering to harvest maturity. Choose varieties with a five to seven day spread in maturity to maximize yield potential. Shorter maturity varieties are at less risk to late-season diseases but limit yield potential. To boost soybean yields, try planting 25 percent of your acres to later-maturing varieties with sufficient disease resistance.
• Grain composition is the amount of oil, protein, and amino acid in the grain. High amounts improve the value of a soybean crop.
• Taller plants are generally more susceptible to lodging. Lodging can reduce yield and make harvest more difficult.

Using yield data to select varieties

Reliable field trial data is the best source of information for soybean producers selecting seed for the next season. Begin by finding the tables which summarize the tests in the district or region in which your farm is located.

The most important aspect of reviewing data involves understanding the data that are provided. When reading the data tables, start by finding the least significant difference, or LSD, value. It is often found in the bottom row of the table. Use the LSD value to help you sort through entries.

• Any entries that differ by less than the reported LSD for a trait (i.e., yield, maturity, or disease rating)  must be considered equal for that trait. For example, if the LSD for yield is 5 bushels, only yields differering by greater than 5 bushels can be considered different from each other.
• Lower values for an LSD give more predictive results and indicate higher quality experiments. Rely more on reports with a lower rather than higher LSD value.
• Any data provided without LSD values should be considered unreliable and should not be used.

The next step is to sort through the data to make your selections. Begin by sorting the data by yield and maturity group.

• Subtract the LSD value from the top-yielding variety. For example, if the top yielder was 70 bushels per acre,  highlight all those varieties with yields from 65 to 70 bushels per acre. This is the high yielding group of varieties.
• Often reports will include averages over 3 years or more, and in several locations in the region. Rely most on these multi-year, multi-location averages.

Continue this process with other plant traits you have identified as important for your fields. It may be better to go through the whole process on all the traits before screening any. The ideal situation would be to select varieties that are the best in all characteristics of interest, but doing this would probably not provide much genetic diversity.

• To ensure diversity, select varieties from different LSD groups in traits that are of less concern for a particular operation, such as seeds per pound or plant height. Choose among different maturity groups.
• Be sure that other important traits are considered along with yield. For example, some relatively high-yielding soybean varieties allow substantial amounts of SCN reproduction, thus worsening an SCN problem. Therefore, in addition to yield, growers must consider how well the variety suppresses SCN reproduction. This is generally identified by the number of eggs in 100cc soil at harvest, and is included in some SCN variety trials, such as the Iowa, Minnesota, and Wisconsin trials.

Do not rely on summary tables or diagrams to determine if one variety is better than another
Learn to look at the data. All data provided without LSD values should be considered unreliable and should not be used to make variety decisions. This point cannot be overstated: using test results without the accompanying statistics will lead to conclusions that are not supported by the test results.

Find your state variety trial results online»
View SCN variety trial reports»

Sources

Using Yield Trial Data to Make Variety Selections - Iowa State University Integrated Crop Management News

Soybean Variety Selection - University of Missouri Extension G4412

Soybean Variety Selection (pdf format) - Iowa State University

Kansas Soybean Production Handbook - Variety Selection (pdf format) Kansas State University

Manage SCN for better yields - Iowa Soybean Association