Alfalfa is a deep-rooted perennial legume highly valued as a forage crop for its high protein content and ability to fix atmospheric nitrogen. Establishing a dense, productive stand requires the correct seeding rate, which directly impacts the crop’s overall economics. Planting the right quantity of seed ensures a robust stand that maximizes yield and persistence over multiple years. The optimal pounds per acre must be calculated precisely, accounting for the specific conditions of the field.
Standard Seeding Rates
The generally recommended range for planting alfalfa is between 12 and 15 pounds of pure live seed (PLS) per acre under ideal conditions. This rate is designed to achieve a target of 20 to 30 vigorous plants per square foot by the end of the establishment year, which is more than enough to achieve maximum yields. Research has demonstrated that planting rates exceeding 15 pounds of PLS per acre often do not result in a higher yield and may simply lead to more seedlings dying off due to overcrowding in the first year.
It is important to distinguish between the actual weight of the seed and the pure live seed (PLS) content. PLS is the fraction of the seed expected to germinate and grow, accounting for both purity and viable germination. When purchasing coated seed, the coating (which may include inoculants and lime) can account for 10% to 30% of the total weight. For example, to achieve 15 pounds of PLS per acre with a heavily coated product, the total weight applied may need to be increased to 24 pounds per acre to compensate for the inert material.
Optimizing the Seedbed for Success
Proper seedbed preparation is necessary for successful establishment and influences whether the standard seeding rate is viable. Alfalfa thrives in deep, well-drained soils; poor drainage quickly leads to disease issues and reduced persistence. Growers should avoid fields where water is known to pool or where the water table is consistently close to the surface.
Soil testing should be performed six to twelve months before planting to assess and correct soil chemistry. Alfalfa requires a near-neutral pH for optimal growth, with the ideal range being 6.5 to 7.5. Targeting a pH of 6.7 to 7.0 maximizes nutrient availability and the activity of nitrogen-fixing Rhizobia bacteria. Since agricultural lime reacts slowly, applying it well in advance allows time for the soil to buffer its acidity before the delicate seedlings emerge.
A firm seedbed is required for maximizing germination and uniform seedling establishment. After any deep tillage, the soil surface should be smoothed and firmed, often using a cultipacker or roller. A simple test for firmness is that a person’s heel should not sink more than half an inch into the soil when walking across the field. This firmness ensures good seed-to-soil contact, which is necessary for the small seeds to absorb moisture and establish roots at the correct depth of 1/4 to 1/2 inch.
Adjusting Rates for Site Conditions
The standard seeding rate serves as a starting point, but site-specific factors require careful adjustments to ensure a productive stand. The method of planting significantly affects the required rate; broadcast seeding requires a higher rate than using a precision drill, which offers better seed placement control. In fields with a history of high weed pressure, a slight increase in the seeding rate can also be beneficial to give the alfalfa a competitive edge against annual weeds.
Soil texture also influences the rate; lighter sandy soils often require a slightly deeper planting depth and may benefit from a higher seeding rate to compensate for less reliable moisture retention. Conversely, in highly managed environments with full irrigation and optimal fertility, a lower rate within the standard range may be used with confidence. The final planting rate should always be calibrated based on the pure live seed percentage listed on the seed tag, regardless of the physical weight of the product in the bag.
Expected Yields and Stand Longevity
A properly established alfalfa stand generally provides high yields for several years, offering a significant return on the initial seed investment. Average annual yields typically range from 8 to 14 tons of dry matter per acre, though intensive farming systems can exceed these numbers. Yields often peak during the second and third production years before beginning a gradual decline as plant density naturally decreases.
The productive life of an alfalfa stand is typically between four and seven years, depending on cultivar, climate, and management practices. Stand longevity is primarily determined by the persistence of healthy plants, which can be assessed by counting the number of stems per square foot. Yield potential generally plateaus at around 50 stems per square foot, a density that allows plants to maximize production without excessive competition. Factors such as root disease, winter injury, and overall stand health determine when to rotate the field out of alfalfa production.