Figure 1 - Lush green alfalfa

Figure 2 - Root systems for alfalfa plants

Family:

• Leguminosae
• Species Medicago sativa L.
• Herbaceous perennial legume not commonly used as an annual cover crop
• Some annual varieties available

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Growth Habits

Germination

• inoculation needed if alfalfa not regularly grown
• slow to establish

Top Growth

• 5 to 25 stems per crown
• growth of 40-60 cm in height

Root System

• tap root
• nitrogen fixing nodules on main tap and lateral roots

Overwintering

• perennial varieties go dormant over winter and generally survive well unless heaving, waterlogging or icing occurs
• cutting or mowing during the "critical fall harvest period" increases the risk of winter injury or winterkill with perennial varieties
• annual varieties continue to grow all fall and will usually winterkill

Site suitability

• performs best on a deep permeable soil – adequate soil moisture but no prolonged periods of standing water
• not tolerant of severely compacted soils
• intolerant of acidic soils (pH < 6.2)

Control Options

• tillage
• herbicides

Weed Control

1. safe to the cereal crop
2. effective on the weeds
3. safe to the cover crop

Sensitivity to Herbicides

Benefits and Cautions

• requires high P and K levels

Pest Management

• provides a break in crop rotation
• host to slugs – a problem for subsequent reduced till crops

Organic Matter

• large biomass producer
• breaks-up some compacted layers

Erosion Control

• excellent cover once established
• improves soil infiltration and permeability

Getting Started

Establishment

• 13 kg/ha seeding rate
• firm seedbed, no till seeding works with care
• shallow seeding depth
• requires adequate seedbed moisture – spring preferred; August seeding is more inconsistent

Cost & Availability

• expensive seed, particularly as a single season cover crop
• perennial seed – widely available
• seed for annual varieties – less available