Revising seed rates in tricky conditions

This week Teagasc released a table of suggested seed rates for winter barley varieties in 2020, based on planting in October, while also taking into account recent wet weather events.

Growers will be applying higher seed rates when they get out to the fields as establishment rates are expected to reduce as a result of wet ground conditions.

It is essential to calculate the correct seed rate when sowing. It ensures you give the crop every chance to reach its potential. No more so than when conditions start to become a little more tricky after wet weather.

Seed rates will increase as time goes on as soils become colder and if seedbeds are not in ideal conditions.

Growers should take the thousand grain weight (TGW) from the bag of seed, but if you’re unsure of the TGW, or of how to calculate it and decide on plant number and germination, then check this table below.

The table gives target plant numbers/m², the required number of seeds/m² and the expected establishment percentage. Expected establishment percentages will change with ground conditions.

There is huge variation in TGWs this season. For example, the TGW figures which are listed below vary from 49.4 to 61.7.

The TGW figures below came from the Department of Agriculture’s variety trials. TGWs will vary between varieties and batches. It should also be noted that six-row hybrid seed rates are lower than conventional varieties.

Data source: Teagasc

¹TGWs from 2020 Department of Agriculture Trials; * Six-row hybrid barley seed rates 220-240 seeds/m².

Calculating Seed Rate

Three figures are needed to calculate seed rate. They are: the target plant population (plants/m²); the TGW of the seed; and the estimated plant establishment percentage.

Use the calculation below, along with the table above, to calculate seed rate.