Agronomy •  2019-04-23

Alfalfa Offers Great Nitrogen Fixation, Storage Benefits

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By Daniel Wiersma, DuPont Pioneer livestock information manager

Alfalfa not only provides extremely valuable, high-protein forage for livestock, it also fixes substantial amounts of nitrogen (N), much of which is stored in the crown and roots. When alfalfa stands are rotated into another crop, such as corn, this stored N is released and becomes available for the new crop to use.

Alfalfa fixes more nitrogen than any legume crop. In fact, a stand can fix as much as 300 pounds of N per acre per year. It uses much of this nitrogen to produce protein in the plant, which growers can harvest and feed to livestock.

In addition to the ability to fix N from the atmosphere, alfalfa is an aggressive scavenger of N in the soil. Water draining from alfalfa fields has been found to contain lower levels of N than runoff from fields containing other crops.

Another benefit of alfalfa is its effect on the soil. Alfalfa produces deep, fibrous roots, with up to five feet of root growth per year, extending 10 to 15 feet or more below ground. These roots cut deep channels in the soil, improving drainage and air circulation within the soil. This allows deeper microbial activity and helps the subsequent crops produce deeper root systems.

As the alfalfa crop dies, the roots decay, releasing stored N into the soil for the succeeding crop. If a grower plants corn after plowing up an alfalfa stand, the corn usually won't require supplemental N. In fact, if the grower keeps the field in corn a second year, residual N from the alfalfa stand often can supply a large share - about half - of that crop's needs.

The residual N from an alfalfa stand can affect crops in that field for up to five years. The benefit for corn can be from 10 to 20 extra bushels per in the first and second years, with benefits still present but decreasing over the next two or three years.

Growers should take advantage of alfalfa's unrivaled ability to fix N, saving fertilizer costs when rotating fields to corn or other crops.

The foregoing is provided for informational purposes only. Please consult with your nutritionist or veterinarian for suggestions specific to your operation. Product performance is variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.​