Soybean-Boosting Bug Enjoys Agronomic Success as New Inoculant

A nitrogen-fixing bacterium developed by Agricultural Research Service scientists can boost farmers' soybean yields while reducing their reliance on commercial fertilizer. That's the latest report from Urbana Laboratories, a Missouri company with an exclusive license from ARS to market the new Bradyrhizobium japonicum strain as an inoculant for soybean seeds.

ARS researchers originally developed, tested and patented the strain in 1991 as an improvement over existing Bradyrhizobium bacteria sold commercially to farmers. This family of soil-dwelling microbes "fixes," or converts, atmospheric nitrogen into a chemical form that soybean plants can use for optimal growth and higher yield. The soybean plant offers the bacteria "room and board" in its roots.

Field studies by the ARS researchers showed their new B. japonicum strain outmatched a top performing bacterial strain by forming 44 percent more nitrogen-fixing nodules on the plants' roots. This is a boon because farmers can apply less artificial fertilizer, reducing their production costs and the chance of groundwater contamination.

Urbana licensed the ARS strain in 1994 and developed inoculant products for sale to farmers the following year. Results from more than 100 field trials in 11 states indicate use of the bacterium boosts yields by an average of 3.5 percent. This can translate to an extra two bushels per acre for the farmer.

Urbana estimates its inoculants containing the new strain have been used on 1.2 million acres of soybeans since 1995, the first year of sales. The bacterium's agricultural success is also the culmination of a 15-year research project that the ARS scientists concluded this fall.

Scientific contact: Jim Hunter, Soil, Plant and Nutrient Research Unit, Fort Collins, Colo., phone (970) 498-4208, fax (970) 482-2909, jhunter@lamar.colostate.edu, David Kuykendall, Molecular Plant Pathology Laboratory, Beltsville, Md., (301) 504-5736, fax (301) 504-6722, or Tom Wacek, Urbana Laboratories, St. Joseph, Mo., phone (816) 233-3446, fax (816) 233-8295, urbana@ponyexpress.net.