How to Grow Alfalfa

Sun

Full sun is required. Eight or more hours of direct sun produces the heaviest tonnage per acre. Six hours is the minimum, and shaded ground simply does not grow productive Alfalfa.

Avoid spots with afternoon shade from windbreaks or buildings. Pick the most open spot on the property for an alfalfa field.

Drainage

Sharp drainage is non-negotiable. Alfalfa roots rot in standing water, even briefly. Walk the field after a heavy rain and mark any spots where water pools for more than a few hours. Those spots will fail and need to be tiled or skipped.

Heavy clay that stays wet is the most common reason an Alfalfa stand thins out within two years.

Soil

Alfalfa prefers neutral to slightly alkaline soil, with the best yields between pH 6.5 and 7.5. Acidic soils need amending with agricultural lime at the rate the soil test recommends, typically applied six to twelve months before planting so it can react with the soil. Without lime correction, an acidic field produces a thin weak stand.

Phosphorus and potassium levels matter more than nitrogen, since the plant fixes its own nitrogen through root nodules. A soil test before seeding is the single best investment in stand establishment.

Space and rotation

For forage and hay, sow at 15 to 20 pounds of seed per acre in rows six to eight inches apart, or broadcast and pack the seed in well. For a small garden cover crop, scatter seed at the same rate per square foot equivalent.

Avoid replanting Alfalfa in the same field for at least two years after the previous stand. The roots release compounds that suppress new alfalfa seedlings, a phenomenon called autotoxicity. Rotate through a cereal crop or row crop before returning Alfalfa to a field.

Watering

In rain-fed systems, established Alfalfa is famously drought-tolerant once the taproot reaches deep moisture, which takes one full growing season. The first six weeks after sowing are the most critical, when the seedlings have shallow roots and need consistent surface moisture.

In irrigated systems, deep infrequent watering on a weekly or twice-weekly schedule is much better than light daily watering. Pre-irrigate before sowing if topsoil is dry to ensure even germination.

Feeding

Alfalfa fixes its own nitrogen, so nitrogen fertilizer is not needed and actually shuts down the root nodule activity. Phosphorus and potassium feeding does matter, with rates determined by the annual soil test.

A topdressing of phosphorus and potassium after each cutting maintains stand vigor and tonnage. Boron is the trace element most often deficient on Alfalfa and is worth checking on the soil test, since boron deficiency reduces yield without obvious symptoms.

When to cut

The first cut of the season happens at bud stage, when about 10 percent of the stems show flower buds but few or no flowers have opened. Cuts later in the season can go a little later, into early bloom, since the plant rebuilds root reserves between cuts.

Three to four cuts per year is typical depending on the climate. In hot dry zones, three cuts is the norm. In long-season irrigated systems, four to five cuts is achievable.

Cutting height

Cut three to four inches above the soil surface. Cutting closer than two inches damages the crown buds that produce regrowth, and the stand thins out faster.

The exception is the final cut of the season, which should be a full six weeks before the first hard frost. This last cut needs to leave enough top growth that the plant rebuilds root reserves before winter, so either skip the last cut entirely or take it earlier.

Stand renovation

After four to six years, stands typically thin out from disease pressure and traffic compaction. Rather than reseed Alfalfa into the same field, rotate to a cereal or row crop for two years before returning. The autotoxicity from old Alfalfa roots suppresses new seedlings sown into the same ground.

Cutting for hay

Cut at bud stage, when about 10 percent of the stems show buds but flowers have not yet opened. Hay cut at this stage carries the highest protein and the best palatability. Cuts taken at full bloom yield more tonnage but lower-quality forage with woody stems.

Let the cut crop dry in the field for two to four days depending on weather, turning the windrows once to speed drying. Bale at 18 to 20 percent moisture for small square bales or higher moisture for haylage in a sealed bag.

Cutting for cover crop

For green manure, mow the crop at flowering and either till the residue into the soil or leave it on the surface as a mulch. A summer Alfalfa cover crop tilled in at flowering adds significant nitrogen and organic matter for the next crop.

Allow at least two weeks between tilling in Alfalfa residue and planting the next crop, since fresh green tissue can tie up nitrogen briefly while it decomposes.

Seed saving

Alfalfa flowers must be tripped by bees to set seed, so seed production requires healthy pollinator populations. Most home growers do not produce seed and instead source it from a reputable supplier each replanting cycle. For seed production, leave a stand uncut through the entire summer and harvest when the pods turn brown and dry on the stems.

Thin stand the first year

Usually caused by acidic soil, poor seedbed firmness, or deep planting. Test the soil before next planting and apply lime well in advance. Prepare a firm seedbed and sow no deeper than half an inch. Overseed thin spots in early fall to fill in the stand.

Yellow stunted plants

Most often nitrogen deficiency caused by failed nodulation, often from skipping inoculant or sowing into very dry soil. Apply a small dose of nitrogen fertilizer to the current crop to recover yield, and inoculate the seed properly next planting.

Plants wilting in hot weather

Verticillium wilt or bacterial wilt kills affected plants and gradually thins the stand. There is no cure once established. Plant verticillium-resistant cultivars in future seedings. Avoid replanting Alfalfa in the same field for at least three years after the disease shows up.

Yellow leaves with brown V-shaped patches

Potato leafhopper feeding damage produces a characteristic yellow V on the leaf tip that gradually spreads. Insecticide treatment is justified only when populations exceed economic thresholds, since leafhopper-resistant cultivars handle most pressure. Cutting on schedule also removes leafhopper populations before they cause major damage.

Holes chewed in leaves

Alfalfa weevil larvae chew the upper leaves in spring, often heavy enough to skeletonize whole plants. Scout fields weekly in spring and treat when populations exceed thresholds. Cutting the first crop on time often controls the weevil without insecticide.

Cottony rot at the crown

Sclerotinia crown rot in wet cool weather kills plants from the crown outward, with characteristic white cottony growth at the base. Improve drainage and avoid overwatering. Resistant cultivars are the best long-term solution for fields with a history of the disease.

Stand thinning after three years

Normal age-related thinning combined with root and crown disease pressure. Plan for replanting after four to six years rather than trying to keep an older stand productive. Rotate through two years of another crop before reseeding Alfalfa in the same field.

Heavy weed pressure

Common in spring sowings without a nurse crop and in stands that have been overgrazed or scalped. A light oats nurse crop suppresses weeds during establishment. Mow at three or four inches rather than scalping the crowns. Established healthy stands shade out most weeds on their own.

Stunted plants with leaf yellowing

Phytophthora root rot in poorly drained fields. There is no rescue once symptoms appear, and the affected areas thin out within a season. Improve drainage with tile or skip the wet spots in future plantings. Plant Phytophthora-resistant cultivars.