Seed viability

Primary symptoms

Poor seed results in poor crop vigor and poor crop establishment.

Crop stands are poor if seed is poor. (Photo AF van Herwaarden)


Is the seed poor?

  • A few days after the first seedlings emerged, count them to check if there are far fewer seedlings than expected from the number of seeds sown? If some of the seeds were dead, this will not show as a patchy crop but as a thin crop, as the dead seeds will have been mixed amongst the good seeds.
  • Are seedlings still emerging ten days after the first seedlings appeared? Do the late seedlings appear weak? Seeds that are old can produce weak seedlings. Dig up some of the weak seedlings. Are they showing symptoms of disease or indications that they have grown around clods? If not, the seed source is probably poor.

Causes of poor seed

  • Seed was stored at high temperature, high humidity or near chemicals. Chemicals diffusing from some manufactured woods and soft plastics can be a problem in unventilated stores.
  • Seed for planting was harvested when the crop was very dry, leading to a high proportion of cracked and broken seed that is dead or, if alive, has too little reserves to grow to the soil surface.
  • The seed was harvested too early and still retained some dormancy. If this is the case, the later seedlings to emerge will appear strong and healthy.
  • Seed was infested with insects or disease.

What you can do about poor seed

  • Germination test: Do a germination test (See below) before planting. Adjust the amount of seed sown upwards to allow for the percentage of bad seed in the sample.

Seed rate needed (kg/ha) = (Desired seed rate (kg/ha) * 100)/Germination (%).

  • Seed storage: Store the seed in a cool, dry and well-ventilated enclosure.
  • Harvest time: Harvest the seed at a time that causes it least physical damage.
  • Sort seed: Remove the damaged seed from the sample sown.
  • Seed age: Do not sow seed that is more than a year old unless a germination test shows it is still good.

NOTE: Do a germination test by counting out several lots of preferably 100 seeds taken from well inside the seed sacks keeping each seed lot separate. Dampen squares of paper or toweling and spread each group of seeds on a towel so the seeds are not touching each other. Cover them with a second damp paper towel. Roll up each sandwich of seeds and put in a plastic bag to prevent the towels from drying out. Keep the bags at room temperature. After 4-5 days count how many seeds have germinated in each lot. Percentage germination is the number of germinated seeds divided by the number of seeds in the sample * 100.