One of the world’s leading agriculture companies – is urging Scottish arable farmers to ease back on nitrogen fertiliser applications on certain newer spring barley varieties grown for malt distilling.

Following recent Syngenta trials in the Borders, Fife and Aberdeenshire, the company revealed that yields of the popular variety, Laureate, and potential newcomer variety SY Tungsten, already contained a high volume of nitrogen without the need for extra above a certain level.

“In the past, some older varieties showed a big yield boost if fertiliser dose was increased, however, increasing nitrogen dose simply risked exceeding the maximum grain nitrogen threshold for malt distilling, thus wasting money,” commented Syngenta malting barley technical manager, Kathryn Hamlen.

“The trials were carried out on 10 sites over four years on Laureate and on six sites over two years on SY Tungsten,” she explains. “The aim was to find the optimum nitrogen fertiliser inputs for yield, while still staying within a maximum grain nitrogen threshold for malt distilling of 1.65%.”

The trial results showed that while Laureate’s yield continued to increase, reaching 8.4t/ha as nitrogen dose was increased from 100 to 125 and on to 150kg/ha, its grain nitrogen content at this highest fertiliser dose became perilously close to the maximum 1.65% threshold – reaching 1.64%.

“Similarly, the yield of SY Tungsten also continued increasing as nitrogen dose was increased up to 150 kg/ha, and its grain nitrogen content, at 1.61%, was also edging towards the maximum threshold. Also on SY Tungsten, increasing the nitrogen dose from 125 to 150kg/ha only resulted in a small yield increase – of just 0.1t/ha,” added Ms Hamlen.

With these results in mind, she explained it doesn’t make sense financially or environmentally to spend money on extra nitrogen on these varieties. For varieties grown for malt distilling, she added that exceeding the grain nitrogen limit risks the grain having to be sold as lower-priced feed.

Growers and agronomists have been encouraged to take into account the individual field situation when assessing fertiliser inputs, however, the optimum nitrogen dose for Laureate and SY Tungsten in the Scottish trials appeared to be sitting at 125kg/ha.

“Laureate has full approval for malt distilling and brewing on the Malting Barley Committee (MBC) approved list for harvest 2021, while SY Tungsten currently has provisional approval 1 for malt distilling and brewing on the MBC list.

"We are hopeful it will gain full approval on the MBC list later this year, so it is worth learning how to get the best from it,” she concluded.