What is seed coating
Seed coating is the application of materials onto the surface of seeds for the purpose of making seeds’ shape, size, weight and seed surface more uniform to make them easier to plant and/or to apply active compounds that improve seed quality and protect the seed from biotic and abiotic stress.
Types of seed coating
There are three types of seed coating:
Film coatingFilm coating utilises a binder which is often a polymer as a fixative to adhere active compounds within the coating to the seed such as fungicides, insecticides or bio-stimulants. Film coating vastly reduces harmful dust from treated seeds as well as producing a smooth surface so that seeds flow easily through processing and sowing equipment. Adding a colour helps in differentiating seeds. Film coating does not change the shape of the seed.
Pelleting surrounds the seed with a shell which increases the size and weight of the seed and ensures a smooth, uniform shape; typically a sphere or ovoid. Pelleting seeds improves their handling and planting efficiency. Pelleting can also incorporate active ingredients with the benefit that the pellet composition protects the seed from contact with phytotoxic compounds.
Seed encrusting is similar to seed pelleting with the primary difference being that encrusted seeds retain more of their original shape. The seed encrusting process still increases the size, weight and uniformity of the seed and improves their planting efficiency. The encrusting process is usually faster and, in some cases, more economical than pelleting.
Benefits of seed coating
Reduced environmental impact
Seed coating has a number of sustainability benefits. For example, applying antimicrobial, fungicidal and insecticidal compounds directly to seeds reduces the amount needed to provide adequate protection. This means less potentially harmful materials are being introduced into the environment. Seed coating further reduces the risk of exposure to plant protection products for both workers and the environment because it dramatically reduces dust-off of these substances. Seed coating also helps towards more efficient farming practices that further contribute to sustainable agriculture.
Efficient planting and improved ease of handling
Mechanical planting of seeds is much more efficient when seeds are a uniform size and shape, have sufficient size and weight to be easily separated mechanically, and flow readily. Seed coating makes light seed heavier, irregular seed more uniform and reduces clumping and dust.
Better crop establishment
An important aim of any seed treatment is ultimately improved crop establishment and seed coating contributes to this in a number of ways. Coating seeds to give them a more uniform shape means less skips and doubles in the drum of the mechanical sowing equipment. This results in improved spacing of seedlings which is beneficial for plant development. It also assists in sowing at the right depth which improves the conditions for germination. Beneficial additives in seed coatings ensure that an accurately controlled quantity is available to the sown species and not to neighbouring weeds.