Earlier nitrogen application bumps up winter barley yields

Winter barley growers should apply a higher proportion of the crop’s nitrogen requirements early to gain a significant yield lift.

Currently, average UK on-farm yield of winter barley is about 6.5t/ha, which is substantially below the potential yield of modern varieties.

The domestic winter barley record stands at 12.2t/ha in the Scottish Borders back in 1989 and trials yields are also hitting more than 12t/ha in some seasons.

Pete Berry, head of crop physiology at Adas, explained current nitrogen recommendations in fertiliser manual RB209 are preventing winter barley crops from reaching their full potential and need to be reviewed to push up on-farm yields of the UK’s number-two crop.

See also: Apply potash and magnesium to boost yields

RB209 advises that 25-30% of nitrogen should be applied before early stem extension (GS 30), with current best field practice considered to be about 30-40% at this timing.

However, HGCA-funded research carried out by Adas is suggesting that proportion should be 50% and can achieve a 0.5t/ha yield increase compared with a 30% split.

“There is a relationship between increased light interception from crop emergence to flowering and increased grains/sq m, which is the driver for yield in barley.

“Unlike wheat, losing green leaf area five weeks after ear emergence won’t have a negative impact on yield, so later N to maintain that isn’t so important,” said Dr Berry.

He added that the total N recommendation was also preventing winter barley crops from reaching their full potential; with an additional 27kg/ha N required every tonne above 8t/ha.

“It goes without saying that the higher the yield potential, the more N you need, and the optimum N rate is about 50-60kg/ha short of where it needs to be.”

The earlier application will result in increased green area in the crop canopy through that crucial yield-fixing period, increasing light interception and providing the yield boost.

However, Dr Berry did urge caution as the larger early split application can result in diluted grain N from the extra yield, which will need to be considered if growing for brewing or distilling markets.

It can also increase crop height by up to 10cm, thus increasing lodging risk and careful plant growth regulation will needed to counteract the effect.

Plant growth regulators (PGRs) are applied to 76% of winter barley crops, with more than half of those applications being the active ingredient chlormequat.

“Growers shouldn’t rely on chlormequat, particularly in high-yielding crops, as it doesn’t have a huge growth regulatory effect.

“Consider other gibberellin inhibitors and ethephon, which can shorten barley by 8-10cm,” Mr Berry told delegates at the recent HGCA Agronomists Conference.