If you plan to inoculate your soybean seed this year, be careful about combining the inoculant with seed treatments, fertilizers or pesticides. The rhizobia in the inoculant can be killed by the wrong chemical combination. The rhizobia are what help soybeans develop nitrogen-fixing nodules on their roots, notes agronomist Denise McWilliams of the University of Minnesota Extension Service. Killing the rhizobia means the time and money spent on inocuation are wasted.

"Combining inoculants with other treatments has become popular due to more use of liquid-based inoculants," says McWilliams.

Urbana Laboratories, which manufactures soybean inoculants, has posted a suggested set of inoculant compatibility rules on the Internet at www.urbana-labs.com/compat.htm.