Spring sowing is underway in many parts of the country. Seed rate should take in a number of factors including the thousand grain weight (TGW) of the seed and the time of sowing.
Seed rate will change from year-to-year depending on the TGW of the variety and the batch of seed. TGW will vary across seed batches.
Before deciding on a seed rate you must know the expected establishment rate; the target plant count/m² and the TGW of the seed.
Once all of those three factors are known you can calculate seed rate using the following equation.
To give an example, a spring barley crop with a TGW of 50g planted in early April should have a target plant count of 300 plants/m² and aim for an establishment rate of 85%. This would give a seed rate of 176kg/ha.
Certified seed should have a minimum germination of 85%. Crops sown in good conditions in the spring time should expect an establishment rate of 85%. The target plant population should also increase as the season goes on for spring crops.
For example, spring barley sown at the end of March should have a target of 300 plants/m², while crops sown in late April should have a target of 325 plants/m² – at an establishment rate of 90%.
