With drilling of winter cereals having already started, there have been many questions posed about the required seed rates for the different crops and varieties.

According to Teagasc crops and potato specialist Shay Phelan, the rates used in 2021/2022 may not be exactly correct for the current season.

This is because the thousand grain weight (TGW) for 2022 crops will have been different than those harvested in 2021. As a result, seed rates may well have to be adjusted to reflect this.

“With ground conditions being very good at the moment there is some scope to reduce seed rates earlier in the season,” Phelan said.

“Rates can be increased again as October progresses. Soil conditions normally deteriorate, where later drilling is concerned. So, seed rates need to be increased to compensate for potentially lower establishment rates.

“The seed rate should be based on the current TGW, which should be printed on the bag.

“For home saved seed it’s a case counting out 1000 grains and weighing them. This will give the TGW for the seed involved.

“However, TGW values may change between batches of seed and varieties so growers should carry out regular checks.”

Barley seed rates

For winter barley crops planted out over the coming week, Teagasc is recommending a target establishment of 80%. This figure is based on the production of 280 plants/m2 from a sowing rate of 350 seeds.

Teagasc has recommended the following seed rates (kg/ha) for a number of winter barley varieties, sown out during the first week of October. These figures are based on Department of Agriculture, Food and the Marine (DAFM) 2023 TGW values.

They are: KWS Cassia (187); LG Casting (182); KWS Infinity (186); Bordeau (189); KWS Joyau (171); KWS Tardis (196); SY Armadillo (1670; Belfry (93); and Bazooka (95).

Sowing date has the greatest influence on early crop development. Later-sown crops pass through their developmental stages faster and complete each stage more quickly than crops sown earlier.

Typically, crops sown several weeks apart will mature within days of each other.

Accumulated mean daily temperature from sowing can be used to measure the ‘thermal time’ (°C days) taken for crops to emerge.

Trial work carried out in the UK at a range of reference sites confirms that crops reached 50% emergence in 150° days.

The thermal time to emergence was greater where dry soil limited germination. In autumn, as daily temperatures decline, crops take longer to emerge but emergence accelerates as temperatures rise in spring.