Soybean Variety Selection

SCN-susceptible (left) and SCN-resistant (right) varieties tested side by side in a field infested with SCN. Photo credit: Palle Pedersen, Iowa State University.

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

The variety you choose will determine the yield potential, 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

Figure 1. Soybean variety selection hierarchy. From:Variety Selection, Palle Pedersen, Department of Agronomy, Iowa State University

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. Also use the data from the replicated, independent yield trials conducted each year at all state agricultural universities in the North Central region.
  Find your state variety trial results online»
  Read below about how to understand and use the variery trial reports.
• 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.

How to use variety trial reports to make variety selections

Reliable field trial data is one of the best sources 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.

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.

Sources

Soybean Variety Selection (pdf format) - Iowa State University

Using Soybean Yield Data to Improve Variety Selection - University of Nebraska

Soybean Variety Selection - University of Missouri Extension G4412

Consider Pests and Diseases When Choosing Soybean  Varieties - NCSRP

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

A fresh view of variety selection (pdf format) - Iowa State University

Choosing an SCN-resistant soybean variety: It's not just about yield - Iowa State University

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

Information on these pages is from the cooperative effort of researchers throughout the North Central states. Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: NCSRP Plant Health Initiative at www.planthealth.info. Please do not use copyrighted photos without permission.