Alfalfa Seed Production Guidelines
Introduction
These recommendations provide general guidelines for alfalfa seed production. Adaptation to local conditions is essential for success.
Field Selection
- Weed Control: Begin with a clean field. Perennial weeds must be eliminated before seeding, as effective control in established alfalfa is limited. Avoid fields with a history of sweet clover to prevent seed carry-over.
- Pre-Plant Management: Start field preparation two years prior to seeding. Certified production requires land free of alfalfa for two years. Avoid rapeseed during this period to prevent volunteer plants; cereals are preferred for broad weed control options.
- Perennial Grass Control: Apply glyphosate (e.g., Roundup) in fall if quack grass or similar species are present.
- Soil Requirements: Alfalfa performs best on deep, medium-textured, well-drained soils. Avoid poorly drained or saline soils.
- Isolation: For certified seed, maintain at least 50 m (165 ft) from other alfalfa fields. Ensure neighbouring fields pose no contamination risk.
- Pollination Considerations: Select sheltered fields to aid bee activity and pollination.
- Seedbed Preparation: Summerfallow the year prior to establishment for optimal results.
Seedbed Preparation
- Firm, Fine Seedbed: Prepare a well-worked, firm seedbed to allow shallow seed placement (maximum ½ inch or 2 cm). A firm bed promotes upward moisture movement for germination.
- Firmness Test: The heel of a shoe should sink no more than ¼ inch (1 cm). Packing may be required, but avoid excessive packing on clay soils to prevent crusting.
- Alternative Practice: Seeding into undisturbed stubble conserves moisture and provides firmness but limits weed control options. Use only the cleanest stubble fields for this method.
Companion Crops
- Use of Nurse Crops: While many growers still use companion crops, planting without one is increasingly common.
Advantages of No Nurse Crop:
o Less competition for light, water, and nutrients
o Greater seedling vigor
o More flexible weed control
o Increased winter hardiness
o Higher seed production in the first harvest year
Disadvantage:
o Increased weed pressure.
o Income loss from omitting a nurse crop is usually offset by higher seed yields in year one.
- Preferred Crops: Flax and canola are recommended. Seed them separately, prior to and at right angles to alfalfa rows to minimize competition.
- Seeding Adjustments: Reduce nurse crop seeding rate by one-third to one-half to lessen competition. This reduction typically decreases nurse crop yield by only 10–20%.
Seeding Rates, Dates, and Row Spacing
- Optimal Plant Density: Highest seed yields occur at 14,000–30,000 plants per acre (35,000–75,000 plants per hectare) in rows spaced 24–48 inches (60–120 cm). Narrower rows and higher densities suit moist regions.
- Recommended Seeding Rate: 0.5–1.0 lb/acre (0.5–1.0 kg/ha). Avoid rates below 0.5 lb/acre.
- Timing: Seed very early in spring to maximize soil moisture and root development before summer heat.
- Avoid Late Seeding: August seedings have less than a 50% chance of success and rarely produce a satisfactory crop the following year.
Variety Selection
- Certified seed generally provides higher returns than common seed with minimal extra cost or labor.
- Certified production requires planting foundation seed of Canadian varieties or registered foreign varieties, following Canadian Seed Growers Association regulations.
- Considerations for Variety Choice:
- Marketability and long-term outlook
- Seed yield potential
- Availability of seed stock
- Consult seed companies for marketing opportunities and stock seed of proprietary or public varieties. Older Canadian public varieties can be sourced through the Canadian Forage Seed Project.
Inoculation and Fertilization
- Inoculate seed with the proper nitrogen-fixing bacteria immediately before planting.
- Best method: dampen seed with water or a sticker solution (e.g., 2 tbsp corn syrup per quart of water), mix inoculant thoroughly, and sow promptly.
- Fertilizer applications are generally unnecessary unless soil tests indicate deficiencies.
Weed Control
- Herbicides are often necessary due to low seeding rates and wide row spacing.
- Without Companion Crop:
- EPTC (Eptam) or Trifluralin (Treflan) preplant incorporated
- Pursuit for grass and broadleaf weeds
- Velpar in fall if stand is well established
- With Companion Crop: Limited herbicide options—consider this when selecting the crop.
- Mechanical control (mowing or haying) is possible but sacrifices seed yield in that year.
- Refer to Manitoba Agriculture Guide to Crop Protection for current recommendations.
Insect Control
- Major pests: lygus bugs, aphids, and grasshoppers.
- Monitor fields regularly and identify pests early.
- Control options include cultural practices (e.g., burning) and selective pesticides.
- Refer to Field Scouting Guide for details.
Harvesting
- Seed matures 5–6 weeks after pollination. Begin harvest about six weeks after bees are removed or bloom ends.
- Swathing:
- Swath when ⅔–¾ of pods are dark brown or black
- Swath damp to prevent pod shatter and in the direction of the prevailing winds to reduce seed loss
- Use rollers or leave standing strips to reduce wind damage
- Straight Combining:
- Desiccate with Reglone or rely on frost
- Combine 3–5 days after desiccation
Stand Maintenance
- Minimal maintenance required for well-established fields.
- Annual weed and insect control programs recommended.
- Spring burning helps manage pests and diseases.
- Monitor stand density—thin back to 30,000 plants per acre (75,000 per hectare) after first or second harvest using cross-cultivation in spring.

