Thin layer coating is done with the aim of applying materials such as dyes or pesticides and nutrients on the seed surface correctly and uniformly and presenting valuable and attractive seeds to the market. The materials used in this method adhere to the seed surface to minimize dusting and loss during transport and seeding. This thin layer should uniformly cover the seed surface, not separate from the seed surface and be permeable to water and not have a negative effect on seed germination. The increase in seed size in this method is small and between one to ten percent and is mainly used in large seeds that are produced in large volumes.

The formulation used in this method is an aqueous suspension consisting of an adhesive, a pigment, and a filler, which is sprayed onto a rotating seed mass and, after drying, forms a thin layer on the seed, and various materials adhere to the seed surface. This formulation is a substrate to which food, pesticides and other substances can be added according to the purpose of coating. Seeds that are spherical and uniform in shape, like canola seeds, are easily coated. But seeds such as beet seeds, lettuce and quinoa are hard to cover. Ready-made formulations for different seeds and for coating with different purposes are prepared and marketed      .

-         Creating a suitable environment for the establishment and rapid growth of seeds (growth stimulants, nutrients)

-         Uniform disinfection and effective control of diseases and pests

-         Effective use of biological materials and low need for fertilizers with low consumption of trace elements

-         Dealing with stresses (drought, salinity and flooding ...) by placing moisture-absorbing materials and organic matter on the seeds

-         Adjusting the emergence time of buds using temperature-sensitive polymers, simultaneous flowering of mother and father lines 

Pellet means deformation and increase the volume of seeds, which is done by placing different materials on the seed coat and with the following goals.

- Possibility of mechanized sowing and precise replacement in the planting bed in depth and with appropriate density, low seed consumption and facilitate seed sowing and no need for transplanting,

-Possibility of placing different layers of nutrients, disinfectants, biological materials, etc. on the seeds,

Pesticides are used during the coating or seed pelleting process and can be used mixed with the coating formulation or placed separately on the seed surface or at intervals in the coating layers. To control seed diseases, pesticides are placed on the seed surface and in cases where they may cause toxicity on the seed surface, it is placed in the cover layers and away from the seed surface. Macro and micro nutrients can also be placed in separate layers on the seed.

The coating created should not have adverse effects on the seeds, should be permeable to water, while having strength on the seed surface, should be easily dissolved in water and should be economical. The most commercial use of pelleted seeds is in sugar beet seeds, which are obtained from almost all European and Japanese crops, and most North American crops come from pelleted seeds. Other commercial-grade pelleted seeds include carrots, celery, chicory, leeks, lettuce, onions, peppers, tomatoes, cabbage, sweet corn, grass, and ornamental flower seeds.

Pelleting is in the early stages of research and development in Iran and has recently become popular in the commercial level of tobacco seeds and to a lesser extent in the seeds of medicinal plants and ornamental flowers.

pelleting can be made less quickly than film coating. They require more care and cost more, and are economically justified in the case of small and expensive seeds.