Talc or Graphite

Talc is a lubricant, but its primary purpose when used in planters is as a desiccant. Seed coatings, especially on corn, tend to be sticky, and get stickier as the relative humidity rises. Sticky seed doesn't flow, and tends to bridge in seed meters and clog in seed delivery tubes. Talc absorbs moisture AND provides lubrication to keep treated seeds flowing freely.

Graphite has been around a long time. It started out as a lubricant back int the OLD plate-type corn planters, and continued to have value as a lubricant in finger-type seed meters. Vacuum planters dimmed the popularity of graphite, but Precision Planting's eSets have just enough mechanical metal parts to benefit from the lubricative qualities of graphite, so "black dust" is once again part of planting.

Now we're seeing blends of talc and graphite, but the reasons aren't as obvious as they first appear. Yes, talc and graphite still make good lubricants, and talc helps reduce the stickiness of seed coatings. But a new reason to use graphite involves all the plastic hoses through which seed is transported on planters with central seed tanks. Hard, dry seed blown through plastic hoses can develop subtle electrostatic charges, enough to "magnetize" the seeds so they tend to clump together. Since graphite is an excellent conductor of electricity, adding graphite to the seed tank eventually coats the inside of the seed tank, seed tubes and everything the seeds touch with a film of electrically conductive graphite. The conductive film helps dissipate any static electricity that develops in the system.