Legume life cycles and characteristics

Forage legumes vary in terms of their life cycle, the amount of nitrogen they can fix, how well they can adapt to challenging conditions and their susceptibility to insect damage and diseases.

By understanding the characteristics of forage legumes, you can better identify, use and manage them on your farm.

Life cycles

Annual, biennial and perennial describe the time required for legumes to complete their life cycles:

  • Annual (e.g., soybean): Germinates from seed, flowers, sets seed and dies within one growing season.

  • Perennial (e.g., alfalfa and kura clover): Live for three or more years once established, and have the potential to set seed each year.

  • Biennial (e.g., sweetclover): An intermediate group of legumes that lives for two years. They grow vegetatively the first year, and flower and die in the second year.

Benefits of perennials

Of the three legume life cycle types, perennials are considered to be the most valuable for the environment.

Perennials provide continuous ground cover, recycling of nutrients and long-term carbon storage. Plus, they eliminate the need for annual reseeding and associated field activities, saving producers time and money.

Nitrogen fixation

Many important food plants like corn, wheat, and oat require nitrogen fertilization for growth and yield. In contrast, properly managed forage legumes are nitrogen self-sufficient.

Legumes vigorously grow without the nitrogen fertilizers required for grasses. They achieve this self-sufficiency through the process of biological nitrogen fixation.

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Adaptability and susceptibility

Forage legumes differ in how well they can adapt to soil and climatic conditions and their susceptibility to insect damage and diseases (Tables 2 and 3).

As a result, various legumes have characteristics that often suit it best for specific uses. This is why being able to identify, use and manage the perennial forage legumes commonly grown in the Upper Midwest can be valuable to a livestock producer.

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Craig Sheaffer, agronomist, College of Food, Agricultural and Natural Resource Sciences (CFANS); Nancy J. Ehlke, department head, agronomy, CFANS; Kenneth A. Albrecht, agronomist, University of Wisconsin-Madison; Jacob M. Jungers, agronomist, CFANS and Jared J. Goplen, Extension educator

Reviewed in 2018

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