Soybean needs rhizobia to fix nitrogen.
Adequate rhizobia will remain in the soil for about three to four years following the last soybean crop. If soybeans have been out of the field longer, then inoculants containing rhizobia (or Bradyrhizobia japonica) may help to ensure adequate nodulation.
If an inoculant is to be used, proper handling and care must be taken to keep the organisms alive, and it must be uniformaly spread in the seed.
If soybeans are grown for the first time in a field and the inoculent was not used, N fertilization will be needed. N rates will be about 200 lbs N/acre, costing about $180/acre. Inoculent will cost $1 to $2 per acre.
For more information on this or other topics related to soybean production, contact your state extension specialist or your local extension educator/agent.
The following is the link to the soybean extension specialists: state extension soybean specialist.
