Please have a look at these PDFs, hope you find them useful...

It's more common to pelletise the seed with cultures rather than spread the culture over/through the soil surface. Mostly it's much cheaper as you use less culture and because you guarantee the roots are in contact with the culture, once the seed germinates.

With subsequent crops the roots are left in the ground and the culture is throughout the soil profile.

Hi,

Thank you for your suggestions. I am trying to study the effect of a metabolite on the nodulation of soybeans. So my idea is to inoculate the soil with the culture and also the metabolite and see how the nodulation is impacted. If I treat the seed with the inoculum, it would bias my study in some way because the bacterial is stuck to the seed so was trying to figure out a way to do this experiment.

It will be an interesting idea to see , which metabolite accumulation is linked modulation intensity , although metabolites are the source of plant defense and usually metabolites function triggers off when plant is subjected to some kind of stress....