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Forage Crops - SOS

Alfalfa (pg 172-174)

Medicago sativa L.

Background

Origin is the Near East 'alfalfa' means 'best fodder' in Arabic Oldest recorded crop grown for forages (over 3300 years) Grown widely across the U.S. to lower Canada Considered the queen of the forage

Alfalfa - the queen of the forages (click to enlarge, 65kb)

Soil Fertility

alfalfa - grown at 2 different pH (click to enlarge, 50kb)

Requires near neutral pH (for nodulation) Requires large quantities of K and medium quantities of P (especially when cut for hay/silage) Produces nodules for N supply if inoculated with N-fixing rhizobia Best-adapted to deep, well-drained, highly fertility soils

Quality

• Highly palatable forage
• Highest yielding legume
• High quality if harvested before full bloom
  

Disease

• Susceptible to many diseases
• Best methods for diseases control include:
  • proper site selection (well-drained soils)
  • newer disease resistant varieties
  • proper soil pH and fertility
  • appropriate harvest schedules
  • controlling insects and weeds
  • minimizing traffic compaction
  • crop rotation
  • Sanitation procedures limit inoculum spread.

Insect Pests

Alfalfa weevil and potato leafhopper (PLH) are the most destructive pests to alfalfa in the Midwest. Other minor pests in the Midwest include meadow spittlebug, pea aphid, clover weevil, clover root curculio (may not be so minor, wounding on root is entry point for pathogens). Various aphids and nematodes are problems in other parts of the country.

Potato leafhopper damage (click to enlarge, 154kb) Leafhopper Resistant (R) vs. Susceptible (L) variety

Advantages

• Highest yielding and quality of all legumes
• Long-lived perennial
• Good seedling vigor
• Deep root system - excellent drought tolerance
• Recovers rapidly after harvest
• Increased resistance to diseases over other legumes

Disadvantages

• Low productivity and stand persistence on poorly drained soils
• Requires high soil pH
• Frost heaving is usually more severe than other legumes

Identification

• First true leaf is unifoliate
• Trifoliate leaves are pinnately compound
• Pubescent are lacking (non PLH resistant varieties)
• Elongated - less than half of the leaf is serrated
• Grows from a crown once established

Agronomy

Old and new varieties under test (click to enlarge, 108kb)

plant at 15-18 lb/ac (lower rates in mixtures) (higher rates for coated seed) old varieties: Vernal new varieties: Over 200 modern varieties available with key traits like disease resistance, traffic tolerance (Ameristand varieties) potato leafhopper resistance (e.g. 54H91, Evergreen-II, Trailblazer), higher forage quality, Roundup-ready varieties in advanced testing

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