High fertiliser costs: implications for milling wheat growers

How should high fertiliser prices influence milling wheat growing strategies in 2022? Sarah Clarke, ADAS, provided some evidence-based answers at the AHDB Milling Wheat Conference.

To form grain protein, wheat requires nitrogen. With fertiliser prices reaching dizzying heights, many growers are questioning whether it still makes financial sense to grow a crop that requires relatively high levels of grain protein.

At the Milling Wheat Conference held on 1 March 2022, Sarah outlined results from a recent AHDB-funded review of nitrogen management.

Sarah said “Increasing nutrient prices change the break-even ratio (BER) – the point at which the cost of applying extra nitrogen is not worth the value of the extra yield returned.

“The ratio for cereals is now around 10:1 and the general advice for feed varieties is to reduce the RB209 recommendation by 50kg N/ha, which would result in a 0.36 t/ha yield reduction.”

As it is essential to factor in milling wheat premiums, ADAS worked with UK Flour Millers and AHDB to model the specific response of milling wheat varieties to nitrogen.

 “We studied 26 milling wheat nitrogen-response experiments and found that the yield response was the same as other types of wheat,” Sarah told the conference

The implications for milling wheat grain protein levels were also explored.

Sarah continued “When fertilising for yield, you would expect to achieve around 11% grain protein in feed wheat varieties. However, in milling wheat varieties, you would expect to achieve around 12% grain protein, which is below the typical milling wheat specification of 13%.

“If you were to reduce the nitrogen rate on milling wheats by 50 kg N/ha, as advocated for feed varieties, it would result in an average 1% reduction in grain protein. This would potentially create an even bigger gap to bridge to meet the milling specification.”

The modelling exercise compared a milling wheat fertilised to achieve 13% protein with a feed wheat optimally fertilised for yield.

It assumed that a milling wheat with an expected yield of 9 t/ha requires 200 kg N/ha to optimise yield with an extra 40 kg N/ha, as recommended by RB209, to achieve 13% grain protein content.

The modelling found that it may still be economically justified to target milling quality, particularly if premiums are around £30/t or more.

However, in situations where there is a high risk of milling wheat specifications not being met (for protein, as well as for HFN or specific weight), then the adoption of a milling wheat strategy should be reconsidered.

High fertiliser prices mean that the cost of failure to secure premiums is greater this year.

The conference also featured the YEN Milling Wheat Quality Awards.

An analysis of data gathered over the several years of the competition is providing useful insights into how best to hit milling wheat specifications.

For example, protein specifications are more likely to be hit if soil conditions, including organic matter, are optimised, and crops are drilled sufficiently early with an appropriate amount of nitrogen applied.

Sarah said “We have also identified a ‘farm factor’ that is a significant component of yield and protein variation. It has been observed in many datasets and has an influence beyond what can be explained by other factors, such as season, soil, weather and location.”

In terms of associations between management factors and grain protein, there were no associations with fungicides or plant growth regulators.

With so much still to learn, including the causes of the ‘farm factor’, ADAS is continuing to build the data set and will conduct further analyses to create clear management guidance.

A three-year programme of milling wheat fertilisation research is set to conclude this year. The findings from the trials-based work will be combined with the latest understanding of nutrient management to revise the AHDB Nutrient management guide (RB209).