Alfalfa: Factors to consider before planting

Alfalfa is a perennial plant, which generally survives for five to 10 years. However, it can survive more than 20 years depending on management practices. Various outcomes can help determine the success of its production; however, the ability of the stand to produce more yields per acre is often one of the main goals. 

With the upcoming growing season, it is important to pay attention to appropriate production practices to obtain the long-term benefits of alfalfa. Below are some key factors to consider before planting alfalfa this season.

Site selection

Choosing an appropriate site is one of the necessary first steps to consider before cultivating alfalfa. The suitability of the site often depends on the topography and type of soil. For proper growth and development of alfalfa, a leveled to gentle sloping – at zero to three percent – well capable, aerated and drained site, with a native soil pH level above seven is required. The soil should be deep enough to have adequate water-holding capacity and allow for proper functioning of the deep root system of alfalfa for adequate growth and development.

Soil testing

Upon selecting the right field, soil sampling and testing is useful in identifying and correcting the deficiencies of the soil nutrients and other soil parameters critical to optimal stand health. A rule of thumb is to test soil samples which are a good representative of the field. 

To clearly understand what is happening in the soil with respect to the soil nutrient reserve, testing the soil along with plant tissue and water testing is often needed. For a new planting, soil testing and nutrient amendment are recommended at least six months prior to planting, to allow for incorporation of the plant nutrient into the soil during tillage.

Seedbed preparation

Seedbed preparation is a major component of a good seedling development during the establishment phase of alfalfa. It prepares the stage for optimal growth and development throughout the growing season. 

Proper seedbed preparation starts from the removal of leftovers of the previous crop through surfacing and tillage. Through the tillage process, crop residues and stubbles are incorporated into the soil to evenly distribute organic matter in the soil. This helps to improve soil infiltration, firm up the soil strata to provide a solid base for seeding while ensuring good seed-to-soil contact, allows a good medium for rooting and favorable environment for crop management. When no-till planting is practiced, the tilling operation and compaction should be applied in a limited area during the planting operation.

Variety selection

As a perennial crop, selecting an alfalfa variety to grow is a long-term investment, which is irreversible. It is, therefore, important to select varieties exhibiting the best performance. This contributes significantly to the crop’s yielding ability, quality, persistence and management, which can potentially be worth thousands of dollars per unit of land area. 

During alfalfa variety selection process, growers need to not only be aware of the yield potential, but also be mindful of the variety’s fall dormancy, pest and disease resistance and winter survival ratings specific to the production region. Prioritizing these varietal characteristics provides a better estimate of the variety’s stand persistence and forage production potentials. When alfalfa grazing is of interest, new varieties specifically for grazing tolerance should be considered.

Time of planting

It is of utmost importance to take into consideration the time of the year when the prevailing environmental conditions such as temperature, moisture and weed pressure are good for an optimum alfalfa seedling germination and crop emergence. In most regions of Western U.S., seeding alfalfa too early during spring planting in cold conditions delays seedling emergence and its potential stand density. 

In the summer, it is not recommended to plant alfalfa due to the potential for increased weed competition. A minimum of six weeks after germination, before a killing frost, is required to ensure alfalfa survival. Therefore, it is not a recommended practice to plant alfalfa too late in the summer due to the high chance of frost conditions, which can damage the emergent young plants. 

No single time period satisfactorily fulfills all the necessary planting conditions. Growers have to decide when to seed alfalfa based on the benefits and drawbacks of each time period depending on their production targets.

Seeding rate, seeding depth and seed-to-soil contact

Ideally, the number of seeds required to achieve optimal alfalfa yield is about 52,000 seeds in one pound. It is equivalent to five to six pounds pure live seeds (PLS) per acre. Seeding rate beyond six pounds PLS per acre does not improve alfalfa’s production. 

However, planting extra seeds provides insurance to high seedling mortality, particularly in years when cool wet weather persists. Alfalfa seed should be placed 0.25 to 0.5 inch deep for medium to heavy textured soils and 0.5 to one inch deep for sandy soils. Shallower seeding may be used when moisture is adequate, while deeper seeding should be used in drier soils. 

A good rule of thumb is about 10 percent of the seeds should be visible on the soil surface. The soil covering the seed needs to be thick enough to provide moisture for emergence and thin enough to allow the seedling to reach the soil’s surface for a good seed-to-soil contact, fostered by proper seedbed preparation – a key to long-term alfalfa forage production.

In summary, the practices required to seed alfalfa for a successful establishment might vary from farm to farm. However, proper planning along with appropriate management practices can help ensure a successful planting and stand establishment of alfalfa for long-term productivity.

Anowar Islam is a professor and the University of Wyoming Extension forage specialist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or mislam@uwyo.edu. Michael Baidoo is a graduate student in the Department of Plant Sciences.