United States Department of Agriculture scientists in St. Paul,
Minnesota, have added a gene to alfalfa that not only makes it tolerant
to acidic soil and aluminum, but also lets it naturally produce more
nitrogen to stimulate plant growth.
Aluminum makes up about seven percent of the earth’s crust, but it only
causes a problem for plants if they are growing in soil that’s also
acidic. When crop roots in acidic soils take in aluminum, the aluminum
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inhibits the roots’ growth, reducing their ability to take up water and
nutrients needed by the plant. This reduces the plant’s yields.
The gene added by the USDA scientists causes the alfalfa’s roots to
produce more organic acids that render the aluminum nontoxic.
About 40 percent of the world’s arable land has acidic soil. Some soils
are naturally acidic, while others become acidic for a variety of
reasons, including overuse of certain fertilizers.
Lime applications on acidic soils are often impractical, and the lime
may not reach the acidic subsoils where roots grow.
In experiments, the genetically transformed alfalfa grew longer roots
in acidic soil that contained aluminum, indicating the roots were more
aluminum-tolerant. But the transformed alfalfa did not grow as well as
standard alfalfa in non-acidic soil.
Alfalfa is an environmentally friendly crop for rotation that improves
soil and breaks pest and pathogen cycles.
Scientists also found the added gene increases the plant’s ability to
transform atmospheric nitrogen into a form it can use to stimulate
growth.
