Occasionally reports arise of soybean fields that have poor nodulation, even when the producer properly inoculated the seed before planting.
As part of the effort to find the reasons for this, a two-year study was conducted to investigate whether seed treatments might be interfering with soybean inoculants, and causing poor nodulation.
Soybean seed treatments provide protection against various seedling pests and diseases. Potential interactions of seed treatment formulations with seed applied B. japonicum bacterial inoculants are of interest as they are in direct contact with each other on the seed surface. Fields that have not had soybeans present in several years, or that has never had soybeans present, may have little to no naturalized B. japonicum present in the soil.
Therefore, the survival of seed-applied bacterial inoculants is critical in these situations for achieving adequate nodulation and nitrogen fixation.
Seven field experiments were conducted at five locations in 2011 and 2012. All locations had varying soybean history ranging from regular rotation to having no previous soybean history.
The seed treatments in these tests had no significant negative effects on the survival and effectiveness of bacterial inoculant when in direct contact on the seed. There was no significant difference in nodulation, plant dry matter, or yield between any of the treatments.
Nodulation performance was analyzed over all seed treatments. Although the performance varied between locations, within the location there was no impact of seed treatment on nodulation performance.
Seed treatment formulations did not significantly affect soybean nodulation or yield. These results imply that seed treatments are not associated with nodulation problems that have been observed in some areas.