Beneficial Fungi Boost Pepper Growth

Beneficial fungi that live on plant roots increased green bell pepper yields by as much as one-third in studies by Agricultural Research Service scientists.

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 Rodale Institute Experimental Farm in Kutztown, Pa., to measure the fungi's effects on pepper yield.

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 given plant.

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.