Moisture content

The moisture content of seeds when they first go into storage can have a significant influence on their viability when they come out of storage. Take a look at Figure 7 (below), which shows the difference in expected survival when seeds at four different moisture contents are placed into storage.

The graph shows the impact of moisture content on seed longevity. The x axis is passage of time. The y axis is the percentage of seeds that will germinate after removal from storage. Four graphs are plotted, corresponding to four different seed moisture contents. At six percent, viability curves off very slowly. For seeds at eight percent moisture content, the S-shaped survival curve is still very shallow, indicating good longevity. At ten percent moisture content, the S-shaped survival curve drops off more steeply, indicating worse longevity. If seeds go into storage at twelve percent moisture content, survival is very poor.
Figure 7: survival of seeds at different moisture contents

Figure 7 shows the expected survival curves – the pattern of decline in viability over time – for chickpea (Cicer arietinum) seeds when stored at 5°C.

If the chickpea seeds are dried to equilibrium at 15% relative humidity and 15°C, we expect them to reach a moisture content of 6%. As you can see, the rate of viability loss at 6% moisture content is very slow. We can predict these seeds will reach the viability threshold of 85% after 114 years. However, if the seeds haven’t been dried sufficiently, they lose viability much more quickly. The 85% viability threshold would be reached after 28 years for seeds that have been dried to 8% moisture content, 9 years for seeds dried to 10% moisture content, and just 4 years if the seeds have only been dried to 12% moisture content.

This emphasizes the importance of seed drying, which you will learn more about in module 4.

Viability thresholds

Temperature