Fungi Boost Pepper Growth
By Jim Core
January 16, 2003
Beneficial fungi that live on plant
roots increased green bell pepper yields by as much as one-third in studies by
Agricultural Research Service
Arbuscular mycorrhizal (AM) fungi colonize the roots of most crop plants and
help plants take in phosphorus and other nutrients from the soil. AM fungi have
been diminished by modern agricultural practices such as tillage, but in many
instances can still make important contributions to productivity, particularly
in organic farming and other systems where little if any chemical fertilizers
and pesticides are used.
David D. Douds, a microbiologist at the ARS
Eastern Regional Research Center in
Wyndmoor, Pa., studied four different types of AM fungi in three plantings from
1997 to 1999. He collaborated with Carolyn Reider, a horticulturist at the
Experimental Farm in Kutztown, Pa., to measure the fungi's effects on pepper
They inoculated seedlings before transplanting them into field plots. One
treatment group contained only the AM fungus, Glomus intraradices; another
treatment comprised a mixture of three other types of AM fungi; and a third,
uninoculated group served as the control. Plants were transferred into
high-phosphorus-soil field plots receiving either composted dairy cow manure or
conventional chemical fertilizer.
Results showed that inoculating peppers with AM fungi boosted fruit yield.
The best results were with the fungus mixture, which increased yields each year
by 14 to 23 percent in plots with added compost, and up to 34 percent one year
in plots with chemical fertilizers.
Proper selection of an AM inoculum is essential, according to Douds, and a
mixture of fungi increases the chance of having the right fungus present for a
Past studies have shown that AM fungi benefit plants grown in low-phosphorus
soil, and that high-phosphorus soils make it harder for the fungi to grow on
plant roots. However, this study's results suggest that using AM fungi in
high-phosphorus soils is a management option that shouldn't be ignored.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.