Soybean

The choice of variety is a key factor in profitable soybean production.  Many varietal characteristics, such as maturity, lodging, and disease resistance, must be considered when selecting varieties to complement a production area. To help producers identify varieties best suited to their particular production situation, the Kansas Agricultural Experiment Station (KAES) conducts performance trials involving more than 200 soybean varieties each year at several locations in the state. A number of important traits are evaluated at each location, and additional characteristics are presented in the report.

• Maturity - The soybean is a short-day plant. All varieties flower more quickly with 14-16 hours of darkness. Some varieties will not produce flowers unless there is 10 hours or more of darkness. Most varieties have a narrow range in which they will mature properly and produce satisfactory yields.
  • The time taken to maturity is of extreme importance in adaptation to a particular latitude. Nine maturity groups are recognized in the United States, each with a narrow range of latitude, ranging from .
    • (Group 0 and I), short, very early-maturing varieties adapted to the short summers and long days of the northern States
    • (Group VIII) tall, late-maturing varieties of the Gulf coast
    • Varieties adapted to Kansas generally are classified in maturity groups III, IV, and V. 
  • With a new introduction it is important to test for adaptation to local conditions. The K-State Soybean Breeding & Genetics web site has more information about current varieties grown in Kansas.
• Stem Termination Type - Soybean varieties are classified on the basis of their morphological growth habit or stem termination type. Two types of growth occur; varieties with terminal inflorescence called determinate; and varieties called indeterminate type in which the stem does not terminate in an inflorescence.  The indeterminate growth habit is typical of most maturity group IV and earlier soybean varieties grown in Kansas.  Maturity group V and later varieties typically possess the determinate growth habit.
• Structure - Most varieties are erect, bushy, pubescent or hairy annuals, 20-180 cm tall, with tawny or grey hair on stem, leaves, calyx and pod.  Soybean is completely self-fertile and is normally self-pollinated. The flowers open early in the morning and the pollen is shed just before or at the time of opening and is shed directly onto the stigma. The flowers are visited by bees and other insects, so that cross-pollination can take place, but this is usually considerably less than 1%.