In many regions with colder climates, such as the Upper Midwest of the United States, the growing season for crops is much shorter than in more temperate regions. In such climates, morning frost is common well into May. Germination of seeds during this time can cause them to perish due to late freezes. Autumn freezes as early as mid-August can compress the growing season into a tight window. It is very important that seeds germinate at the optimum time so that they attain maturity during the short growing season. Selvol Polyvinyl Alcohol (PVOH) is used in seed coating formulations to improve crop viability and yield. The coating of delays germination until the ideal temperature and moisture content of the soil is reached, then ruptures upon germination, maximizing the chance that the seed survives to produce a mature plant. Adjusting the hydrolysis level of the Selvol coating can protect a seed until a specific moisture range is met. Thin coating can also serve as a binder or “sticker” for fertilizers, fungicides, or other coating materials that improve crop yield.
Selvol Polyvinyl Alcohol is equally useful as a seed coating in hot, arid climates since the coating will maintain its integrity until the moisture content is high enough to induce germination. A great example of Selvol coatings in warmer climates is the cotton seed. Cotton seeds will only germinate above 60F or 16C. They require sufficient moisture to wet the root system but also need time to dry over a 4 to 15 day to germination process. Selvol PVOH is used to coat cotton seeds, allowing flexibility on sowing timing. The Selvol coating also smoothes the lint and prevents seed entanglement, reducing the need for mechanical delinting or acid delinting and increasing culled seeds.
Many different grades of Selvol Polyvinyl Alcohol are suitable as seed coatings or as part of a seed coating formulation, but the most common grades are the partially hydrolyzed grades, Selvol 203, 205, 523, and 540. A 4-10% solution of Selvol is typically used, depending on the desired coating thickness and viscosity. A variety of seeds benefit from coating with Selvol, including barley, sunflower, corn, rape, cotton, flax, beets, and tomatoes. One study on the viability of corn seeds in the prairie provinces of Canada resulted in over 80% crop emergence for coated seeds compared to 0% emergence for uncoated seeds. Another study found polyvinyl alcohol to be a superior binder for a variety of organic matter than many other water soluble polymers such as PVP and high molecular weight PEG.
Selvol Polyvinyl Alcohol is generally available in resin form, ready to be solubilized into a solution by customers. Selvol PVOH is also available in a ready to use form for customers with limited equipment. Sekisui’s Houston Technology Center helps customers to create innovative solutions for various processing equipment and agricultural environments across the planet.