Many crop fields were waterlogged for long periods of time in 2019. Consider inoculating soybeans that are being planted into these fields this spring. Legumes are able to fix nitrogen from the air, but that requires the roots to form nitrogen-fixing nodules. Soybeans need five pounds of nitrogen to produce one bushel of grain, so to produce 60 bushels of soybeans, it takes 300 pounds of nitrogen. Soybeans can obtain most of this nitrogen from the nitrogen fixing bacteria, but good nodulation is essential.

Nodulation occurs when rhizobia, which are living bacteria, penetrate the root hairs creating nodules after the soybean seed germinates. Soybeans planted into soils that have been flooded for more than one week may benefit from inoculation. The lack of oxygen in flooded soil is detrimental to the rhizobia population.

The strain of rhizobia that colonize soybean is specific to soybean. If soybeans will be planted in a field that has not had soybeans for the three years or more, it is crucial to inoculate the seed. This will ensure an adequate rhizobia population to optimize yield. Soybeans planted into soils with a pH below 6.0 or sandy soils may also benefit from inoculation.

Inoculant is generally applied just prior to planting. The rhizobia will stay viable from a few hours to a few days once the package has been opened. The rhizobia are a living organism and care must be taken to avoid exposing the packages to direct sunlight or extreme heat which cause the bacteria to die. Another option is encapsulated products which have a life of up to 60 days.

For more information contact Valerie Tate, Field Specialist in Agronomy for University of Missouri Extension in Linn County at tatev@missouri.edu or call 660-895-5123. MU Extension programs are open to all.

Valerie Tate is a field specialist in agronomy for the University of Missouri Extension in Linn County.