With the recent hikes in nitrogen fertiliser prices, which now reach as high as £465/t for ammonium nitrate (as of 27 September), farmers are being advised to drop default nitrogen rates to improve their return on investment.

For those who are likely to purchase more than half of their total fertiliser requirements, based on current pricing, an economic optimum of 160kg/ha of nitrogen (N) is recommended.

For years, the standard rate of 220kg N/ha has been optimal, but the recent economic change has shifted this position.

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Natalie Wood, country arable agronomist at fertiliser company Yara UK, suggests this is not the year to be pushing for yields and that the first 160kg N/ha applied will see the greatest return on investment, even at increased fertiliser prices.

Keep a close eye

Growers are recommended to keep a close eye on crop requirements by monitoring crop N levels to manage risk throughout the season.

“When it comes to the final 50kg N/ha, where the return on investment isn’t as high, that’s when tools can assist such as N-testers.

“It will help you see whether it’s right to consider that additional application depending on crop economics, with the potential to push for yields after doing so,” says Ms Wood.

However, she admits that for some soils 160kg N/ha won’t be enough and that as nitrogen rates are cut, yield sensitivity risk will increase, making variable-rate applications even more valuable for avoiding unexpected losses.