Blog: How should farmers manage costly nitrogen fertilisers?

Farmers are considering how much nitrogen to apply in the spring. AHDB’s crop nutrient management specialist Dr Georgina Key explains how new guidance helps farmers adjust their use of costly nitrogen fertilisers and the likely effect this will have on yield.

The widely-reported energy crisis may have caused our domestic energy bills to increase, but it has also led to shortages of carbon dioxide and nitrogen fertilisers.

Significantly reduced production, in the UK and on the continent, has led to prices of nitrogen fertilisers increasing dramatically. Over the past few months, the price rise of fertiliser has outpaced prices for grain. As such, it may be necessary to reduce nitrogen fertiliser applications in the spring to ensure they are still at an economically optimum level.

AHDB’s Nutrient Management Guide (RB209) provides guidance on the economic optimum application rate for a range of cereal and oilseed crops. These recommendations are based on a set ratio between the price of grain and fertiliser.

Today (9 November 2021) AHDB has published updated guidance on how to adjust application rates based on the price of grain, rapeseed and fertiliser. The new guidance, compiled by ADAS, takes account of the dramatic price rises seen recently.  

Tables 3.1 and 3.2 guide farmers on how much to adjust their application rates by, depending on the price of grain or rape seed and fertiliser. The guidance has been extended to account for grain prices up to £300/tonne, rapeseed prices up to £700/tonne and nitrogen fertiliser prices up to £2.50/kg N.

Importantly, AHDB has also published the likely effect of reducing nitrogen fertiliser applications. Table 3.3 shows that reducing nitrogen fertiliser applications by 60 kg N/ha to a cereal or oilseed rape crop would, albeit at the economic optimum level, likely reduce yield by 0.5 t/ha and 0.2 t/ha respectively.

Table 3.1: Extended version of RB209 Table 4.22 to embrace current prices and trends for cereals.

Table 3.2: Extended version of RB209 Table 4.22 to embrace current prices and trends for oilseeds.

Table 3.3: Effect on grain yield of adjusting N applied from the optimum at a break-even price ratio of 5 kg grain per kg N for cereals or 2½ kg seed per kg N for oilseeds.