If microbial inoculants are to be effective as seed treatments they need to remain attached to the seed until they arrive in the soil. Some products, such as mychorrizal fungi inoculant, can have a fairly large particle size, and does not stick to seed very well, particularly smooth seeds such as beans.

The last thing we want to see is accumulated inoculant at the bottom of the seed hopper when we get done planting.

When you apply seed treatments yourself, lightly spray a sugar-water solution onto the seed before the inoculant is applied. This serves to make the seed slightly sticky, and microbial powders remain strongly attached to the seed.