Seed Pelleting

Many useful seeds are too small, too light or too oddly shaped to sow accurately. Pelleting wraps each one in a shell of clay, or clay mixed with compost, until it is a round bead of even size. The seed itself is untouched, and the shell breaks apart once it meets moisture in the soil. Two different jobs sit inside the one practice. In a market plot the even size lets a precision seeder, a machine that takes up one seed at a time and sets it at a fixed spacing, handle lettuce, carrot, onion, beet and basil, which saves thinning them later. In restoration sowing the added weight lets small light seed be thrown accurately instead of drifting, and the shell can carry compost or inoculant in with it.

Everything then depends on that shell opening. It has to take up water and split before the seed inside can germinate, so the seedbed must be kept moist until the seedlings are up. A bed watered once and left dry does worse with coated seed than with the same seed bare, because the coating stands between seed and water. A shell too hard or too compacted delays emergence or stops it, so the treatment meant to raise establishment can lower it, and species differ sharply in how they respond, even close relatives. Mixing sawdust, manure, ash or straw into the clay has been found to beat clay alone.

Making pellets is bench work: seed is tumbled in a rotating drum under the coating and left to dry, needing no special tool or trade. The cost comes afterwards. Coating turns seed that keeps for years in a cool dry place into something short-lived. Held beyond two years it may germinate poorly, swings in humidity break the pellets up, and seed primed as well as coated should not be kept past a season. Small batches coated close to sowing sidestep most of that, and a germination test is the only check that a coating has not gone hard. Nothing is left to maintain in the field.