Switching to urea could offer significant savings for growers of feed wheat, but milling wheat growers or those on thinner soils should stick with ammonium nitrate.

Speaking at the AICC conference last Wednesday (13 January) TAG’s Stuart Knight told agronomists there was no consistent yield penalty from spreading urea instead of ammonium nitrate on medium to heavy soils.

Those planting winter feed wheat were most likely to benefit with gross margins for Group 3 and 4 wheats averaging £3.78/ha more than when using ammonium nitrate, he said.

But this advantage was lost when growing higher-protein Group 1 and 2 varieties, he added.

“Urea is more likely to depress grain protein than ammonium nitrate which reduces its cost effectiveness on breadmaking wheats,” he said. “This is particularly evident with early and late application timings.”

This meant ammonium nitrate gave a £9.59/ha advantage over urea on Group 1 and 2 milling wheats, he said.

The penalty from switching to urea was also greater on thinner soils over limestone or chalk, said Dr Knight.

“Trials indicate that urea delivers consistently lower yields than ammonium nitrate and the problem becomes greater the later the application timing strategy,” he said. “There is a good case for avoiding urea fertilisers on these soils.”

Grain protein was also lower when using urea on thinner soils, he noted.

On average across all 59 trials sites the yield difference between ammonium nitrate and urea was insignificant however, said Dr Knight. “On average there was only a 50kg/ha yield advantage when using AN over urea, he said. “So it’s too finely balanced to tell the difference.”

Spreading urea prills could be challenging, but granules weren’t usually a problem, he noted.

Oilseed rape trails delivered similar results with urea giving a marginal yield advantage over ammonium nitrate, he concluded.