The lucerna plant, commonly known as alfalfa (Medicago sativa), is a perennial flowering plant in the legume family, Fabaceae. It holds significant global importance as a forage crop. Cultivated since ancient Greek and Roman times, alfalfa is one of the longest-used plants for animal feed. Originating in semi-arid Asia Minor, its historical use highlights its adaptability and value in agriculture.
Plant Characteristics and Varieties
Alfalfa is characterized by a deep, extensive taproot system, often reaching 15 to 20 feet or more. This deep rooting contributes to its drought tolerance and ability to access deep soil nutrients. The plant typically grows 2 to 3 feet tall with upright stems. Its leaves are trifoliate, composed of three oval-shaped leaflets. Alfalfa produces clusters of small, pea-like flowers, commonly purple or blue.
Alfalfa varieties are categorized by flower color, including purple and yellow-flowered types, and their hybrids. Yellow-flowered types often show increased drought tolerance, winter hardiness, and slower regrowth. Varieties are also classified by fall dormancy, which indicates their growth response to decreasing day lengths and temperatures, affecting winter survival and yield. Modern breeding has developed varieties with enhanced pest and disease resistance.
Primary Uses and Benefits
Alfalfa is a high-protein forage crop for livestock like cattle, horses, sheep, and goats. Its protein content, typically 18-24% on a dry matter basis, and excellent digestibility make it a superior feed source. This nutritional profile supports high milk production in dairy animals and healthy weight gain in beef cattle.
Beyond feed, alfalfa enhances soil fertility through nitrogen fixation. It forms a symbiotic relationship with bacteria in its root nodules, converting atmospheric nitrogen into a usable form. This process can fix substantial nitrogen, reducing the need for synthetic fertilizers. Alfalfa’s deep root system also improves soil structure, enhancing drainage and air circulation. As a perennial cover crop, it helps control erosion, increases soil organic matter, and provides nitrogen benefits for up to five years in crop rotations.
Cultivation Essentials
Successful alfalfa cultivation requires proper site selection, favoring deep, well-drained soils. The plant thrives in neutral to slightly alkaline conditions, with an optimal pH of 6.5 to 7.5, essential for effective nitrogen fixation. Alfalfa also needs full sun exposure and temperate climates.
Before planting, thorough seedbed preparation is crucial for good seed-to-soil contact and weed control. Alfalfa seeds can be sown in autumn or spring, with spring being common. A typical seeding rate for pure stands is 15 to 20 pounds per acre, adjusted by planting method and soil. Seeds are usually planted at a shallow depth of 1/4 to 1/2 inch.
While alfalfa is drought-tolerant due to its deep roots, consistent moisture is necessary for high yields, especially during establishment and dry periods. Nitrogen fertilization is minimal due to its fixing capabilities, but phosphorus and potassium may need supplementation based on soil tests. A 5-ton per acre crop can remove significant amounts of these nutrients. Pest and disease management involves selecting resistant varieties and maintaining proper cultural practices.
Harvesting and Post-Harvest Handling
Optimal harvesting balances yield and forage quality. For high-quality hay with maximum protein, cutting is recommended at the early bud to early bloom stage, or when plants reach about 28 inches. This stage yields a product with high digestibility and protein. Multiple cuttings are possible per season, with 3 to 4-week intervals for adequate regrowth and stand persistence.
Alfalfa can be harvested as hay, silage, or green chop, with baled hay being common. When cutting for hay, a height of about 7 cm (2.7 inches) promotes healthy regrowth and stand longevity. Drying alfalfa for hay requires careful management to preserve leaf quality, as leaves are the most nutritious part and prone to shattering if dried too quickly. Spreading cut alfalfa in a wide swath accelerates drying. Proper storage, such as baling at optimal moisture (around 20% or lower for dry hay) and protecting bales from weather, prevents spoilage, heating, and nutrient loss.