Soybean Variety Selection and Adaptation

By Hans Kandel, NDSU Extension Agronomist
and Ted Helms, NDSU Soybean Breeder

Selection
Soybean variety selection should be based on maturity, yield, lodging, iron deficiency chlorosis tolerance, and disease reaction.

Later maturing varieties tend to yield more than early maturing varieties when evaluated at the same location. For this reason, it is only relevant to compare yield of varieties that are of similar maturity. Although later maturity increases yield potential, later maturing cultivars are more risky to grow than earlier maturing cultivars because an early fall frost may kill a late maturing cultivar before the beans have filled the pods, which will greatly reduce yield.

Maturity is the first consideration when choosing a variety suited to your geographical region. Cultivars of maturity groups 00, 0 and 1 are suitable to eastern North Dakota and northwestern Minnesota. Maturity group 00 is very early and primarily grown in the northern Red River Valley. Maturity group 0 is adapted to Traill, Cass, Richland, Barnes, Sargent and Richland counties. Maturity group 1 is primarily suitable for southern areas. These maturity groups are further subdivided. For example, a 0.1 maturity group is an early group 0 variety and a 0.9 is a later maturing soybean in group 0.

Soybeans respond to day length and heat units, so the actual calendar date a variety will mature is highly influenced by latitude location as each variety has a narrow range of north to south adaptation. Soybean yield and quality are affected if a season ending freeze occurs before a variety reaches physiological maturity.  Dates of maturity are listed in the performance tables and indicate when the plants of a variety are observed and estimated to be physiologically mature.  Usually harvest can commence approximately 7 to 14 days after the soybeans are physiologically mature.

The best way to select a high yielding variety is to use data averaged across several locations and years. Because weather conditions are unknown in advance, averaging across several years’ data will identify a variety that will likely yield well across different weather conditions. For example, in one year there may be a dry August and in another year there may be adequate moisture during seed filling in August. Selecting a variety that has performed well in dry and moist conditions is the best way to identify a cultivar that does relatively well, regardless of climatic fluctuations.

Some varieties have phytophthora root rot resistance genes. Each gene for resistance confers resistance to different races of phytophthora. A gene may confer resistance to Race 3 but not Race 4. Select a cultivar which has resistance to the common races in your area. Races 3 and 4 are the most common in the Red River Valley and North Dakota. Phytophthora root rot tends to be more of a problem in the southern part of the Red River Valley and more of a problem on poorly drained, heavy soils.

Iron Defeciency
Iron deficiency chlorosis (IDC) is a major problem. Iron chlorosis symptoms are present during the two to seven trifoliate leaf stage. Plants tend to recover and start to turn green again during the flowering and pod filling stages. However, IDC during the early vegetative stages can severely reduce yield. Some varieties are more tolerant to IDC than others. For high pH soils, select an iron chlorosis tolerant variety of suitable maturity that is high yielding. Dr. Jay Goos’ IDC scores for 2007 are incorporated in the 2007 Roundup Ready summary table and can also be found at www.yellowsoybeans.com.

Soybean Cyst Nematode (SCN)
The soybean cyst nematode (SCN), Heterodera glycines, is a small plant-parasitic roundworm that attacks the roots of soybeans. Soybean cyst nematodes are now found in Cass and Richland Counties of North Dakota and are causing yield losses in infested fields. Crop rotation is one of the most important management practice growers must use to control the nematode disease. Growers may want to send soil samples to a laboratory, such as the NDSU Plant Diagnostic Lab (PO Box 5012, Fargo ND 58105. Telephone 701-231-7854), to determine SCN egg numbers. Such information is useful for SCN management. Varieties with resistance to SCN should be used if a field has a nematode problem.  For performance of adapted SCN resistant soybean varieties see figure 1. 

Data in the Following Tables
The presented data in the summary table is a quick overview of soybean variety trial results for 2007.  The yields are reported as a percentage of the location mean where the variety was tested. Variety information was only included if there were at least three test locations available.  Most of the varieties in the table are being offered for sale by the respective companies. Experimental lines or lines not offered for sale are not reported in the summary table.

How To Use This Data
Producers are encouraged to look at the tables on pages 18 and 30-36 for a quick overview of the yield across different sites. The yield is expressed as the mean of the test location. If the number is 100 it indicates that the yield was equal to the mean of all varieties tested at that location. If the number is higher than 100 it indicates that the yield was higher that the trial mean. The last column provides the mean of all observations for that variety. However the total number of observations resulting in the mean in the last column differ. The full information of each location is available at
www.ag.ndsu.edu/variety/soybean.htm.

Soybean Variety Selection Spreadsheet Online
Access a full copy of all of the data from the tables included in this issue of Prairie Grains, along with data that is not included, by visiting www.smallgrains.org/soybeanvarieties.xls.   The file is a Microsoft Excel spreadsheet which you can manipulate to show the data that best fits your farming operation.

All North Dakota Variety information can be found at:
www.ag.ndsu.edu/variety/soybean.htm

A spreadsheet with the tables in this article and all detailed trial information of all reported locations has been prepared and the electronic version can be requested by e-mail: hans.kandel@ndsu.edu.  It is also available online at: www.smallgrains.org/soybeanvarieties.xls

Official University of Minnesota soybean variety information can be obtained at www.soybeans.umn.edu/home.htm.

South Dakota State University information can be found at:
http://www.plantsci.sdstate.edu/varietytrials

2007 NDSU Roundup Ready Soybean Central Region Fee Testing - view the tables online at 2007 Soybean Varietal Information