Alfalfa Improves and Protects Valuable Soil
The importance of alfalfa for hay production is well known. But, alfalfa also plays an essential role in soil sustainability. Not only does alfalfa help prevent soil erosion, but it also protects and improves the soil with its protective canopy, deep root system, and ability to fix atmospheric nitrogen.
Soil erosion is a major problem in agriculture. Valuable soil is permanently lost each year due to wind and water erosion, overgrazing, and poor agricultural practices. Many crops require cultivation one or more times during the growing season to remove weeds. Alfalfa is one of the few crops that requires little to no cultivation once it is established, and as a result, soil loss from wind and water erosion is dramatically reduced.
As alfalfa grows, it quickly forms a dense canopy that covers the soil and protects it from wind and water erosion and reduces runoff. The dense canopy also suppresses the growth of weeds that are common in annual crops. Moreover, frequent cutting prevents weed seed production, which may reduce herbicide use in subsequent crops.
Unlike most other crops, the root system of alfalfa descends deeply into the soil - 9 to 16 feet. This deep and extensive rooting system is very beneficial to the soil. The deep and far-reaching roots hold the soil together. In addition, the root system creates spaces and channels in the soil that aid water movement, which is beneficial to the current crop but may also enhance efficiency of water use in subsequent crops.
Natural chemicals exude, or ooze out, from alfalfa roots and contribute to the creation of an optimal environment for the growth of microorganisms in the immediate vicinity of the roots (otherwise known as the rhizosphere). Organic acids produced by the alfalfa rhizosphere improve soil structure around alfalfa roots. Soil particles aggregate and the soil becomes crumbly, which is beneficial for air and water movement.
Nitrogen is the foundation of plant protein. Many cereal crops require thousands of tons of nitrogen fertilizer each year to achieve peak production. In comparison, alfalfa requires essentially no fertilizer for optimum growth. Bacteria that live symbiotically in alfalfa root nodules are capable of converting (or fixing) nitrogen gas from the atmosphere into useable forms of nitrogen which are available to the current crop and increases the nitrogen concentration in the soil, essentially providing “free” fertilizer to subsequent crops.
A field of alfalfa is a beautiful site. The lush green forage is an economically important crop that is turned into a high quality feed source for dairy cows, beef cattle, horses, and other livestock. Furthermore, the deep and extensive root system of alfalfa and its ability to fix nitrogen protects and improves soil. As such, alfalfa is a valuable part of sustainable agricultural systems.
Putnam, D., M. Russelle, S. Orloff, J. Kuhn, L. Fitzhugh, L. Godfrey, A. Kiess, and R. Long. 2001. Alfalfa, Wildlife and the Environment. The Importance and Benefits of Alfalfa in the 21st Century. California Alfalfa and Forage Association, Novato, CA.