What affects seed viability most?

Seed viability depends largely on three factors: storage temperature, humidity and seed age. Optimum conditions are 35-40°F (2-4°C) and <40% relative humidity. Exposure to oxygen and light also hasten deterioration. Seed life can be greatly increased by sounds storage in airtight containers.

Unlike fluctuating temperatures, constant chill contributes to seed loss through deterioration. Most seeds will remain viable between 3 and 5 times longer at 38°F (3°C) than at room temperature if refrigerated. Freezing at 0°F ( -18 °C) is best for long-term storage. Still, seeds must have 8 percent moisture or less before freezing. This prevents seed loss by keeping seeds in vacuum-sealed jars with silica gel bags.

Humidity control is essential because moisture is the source of respiration and decay. Fungi thrive in environments with relative humidity above 50%, and seeds will rot rapidly. Desiccants enable storage containers to be maintained at a humidity level of 30% or below. Oxygen absorbers retard decay by preventing oxidation of seed oils and proteins.

The germination capacity of seeds decreases with age, even when they are provided with optimal conditions. Tomato seeds will decrease in viability by about 10% each year after the third year. This means that seed tests should be conducted on the older seeds using germination or tetrazolium tests, and the plantation should be arranged accordingly based on the test results. For instance, I plant about 50% more seed when the viability is below 70%.

Exposure to light leads to seed breakdown due to photochemical processes. Seeds should be stored in opaque containers or kept in dark locations to prevent exposure to light. Oxygen causes rancidity in oily seeds, such as sunflowers. Oxygen absorbers should be used with these types of seeds. Proper handling of seeds is essential to ensure the complete benefits of your seed investment year after year.

Read the full article: Seed Viability Test Guide: Ensure Your Seeds Grow