Alfalfa (Medicago sativa) is a perennial legume widely recognized as the “Queen of Forages.” Cultivated globally primarily for livestock feed, it provides high protein and nutrient content for dairy and beef cattle. Its extensive root system contributes significantly to soil health by improving structure and fixing atmospheric nitrogen through a symbiotic relationship with specific soil bacteria. As a long-lived crop, careful management from initial planting through multiple years of harvesting is required to ensure a productive stand.
Essential Environmental Requirements
Alfalfa thrives in deep, fertile soils that allow its extensive taproot system to penetrate freely. The plant’s roots can grow several feet deep, which makes it tolerant of dry conditions once fully established, but it cannot tolerate saturated soil conditions. Fields with poor internal drainage or waterlogging quickly lead to root rot and stand failure. Alfalfa prefers a near-neutral pH range, optimally between 6.5 and 7.5. If the soil is too acidic (below pH 6.2), agricultural lime must be applied well before planting to adjust the chemistry, facilitating nutrient availability and bacterial activity. The plant requires ample sunshine and consistent moisture during its active growth phases, as adequate water is necessary for high-yielding production.
Planting and Initial Establishment
Successful establishment begins with selecting the appropriate planting window, typically occurring in early spring or late summer. Late summer planting is often preferred, allowing seedlings six to eight weeks to establish a robust root system before the first hard frost. The seeds require inoculation with Rhizobium meliloti bacteria just before seeding. This specific strain forms root nodules that capture atmospheric nitrogen, making it available to the plant.
Alfalfa seeds must be placed shallowly, ideally between one-quarter and one-half inch deep, as small seedlings have limited energy reserves. Farmers often use a drill to ensure precise depth and spacing, though broadcasting followed by light harrowing can also be effective. Achieving good seed-to-soil contact is necessary for uniform germination and emergence. The first 60 to 90 days are critical, as the young stand is vulnerable to competition from weeds.
Weed control is a significant challenge during establishment. Growers must employ timely herbicide applications or mechanical methods to suppress weeds, allowing seedlings to develop their crown and deep taproot system. The first “harvest” is often a light clipping intended only to manage weeds and should be timed to allow the crown to fully mature before the first winter.
Managing an Established Alfalfa Stand
Once the alfalfa stand has survived its first winter, the focus shifts to long-term fertility and pest management to maintain high yields. Mature alfalfa stands generally do not require supplemental nitrogen fertilizer because the Rhizobium bacteria efficiently fix atmospheric nitrogen. However, the crop has a high demand for phosphorus and potassium, which are removed from the soil with every harvest.
Annual soil testing is utilized to determine the necessary amount of these macronutrients to replace what is removed, ensuring sustained plant vigor. Micronutrients such as boron may also be required in certain regions, as deficiencies can impede growth and yield potential. While the deep taproot makes established alfalfa drought-tolerant, supplemental irrigation during prolonged dry periods can significantly increase biomass production, especially during regrowth cycles following a cutting.
Pest management is a continuous effort, with several insects posing threats to foliage and overall plant health. The alfalfa weevil and the potato leafhopper are two common insects that cause economic damage. Weevil larvae feed on new growth, while the leafhopper causes “hopperburn” by injecting toxins during feeding. Integrated Pest Management (IPM) strategies, which combine scouting, natural controls, and targeted pesticide use, are employed to keep pest populations below economically damaging thresholds. Perennial weeds that emerge in subsequent years also require careful control to prevent them from displacing the alfalfa plants and reducing stand density.
Harvesting Cycles and Stand Life
Harvesting alfalfa involves balancing maximum yield with the highest possible forage quality, which is determined by protein content and digestibility. The ideal time for cutting is typically when the stand reaches the late bud to one-tenth bloom stage. Harvesting at this early stage maximizes the concentration of protein and total digestible nutrients, though it results in lower tonnage compared to later cutting.
The stubble height left after cutting is crucial for the plant’s ability to recover quickly. Leaving a cutting height of three to four inches protects the crown and leaves enough stem tissue for rapid regrowth and carbohydrate storage. Depending on the climate, a stand can be harvested three to six times per year. Productive stand life generally ranges from four to seven years before yields decline due to factors like disease, weed encroachment, or winterkill.