Higher quality products increase productivity and reduce environmental risks
NEW CROP NUTRITION THINKING
New ways of looking at how growers use fertilisers could help meet increasing demands for protecting environmental assets whilst potentially increasing farm profitability which together with getting the most out of bought-in fertilisers will be one of the most important management areas for UK crop producers in the coming years, says CF Fertilisers arable agronomist Allison Grundy.
It’s been driven from many directions, but one is the Clean Air Strategy which clearly outlines the role agriculture plays in contributing to ammonia emissions and identifies ways in which this can be reduced.
Nitrogen fertilisers contribute 25% to the total Ammonia emissions produced by agriculture and one proposed solution is a move away from straight urea, due to its higher rate of Nitrogen loss to the atmosphere at application. Fortunately for growers, many of the practices that prove beneficial for the environment also improve production efficiency on-farm. High productivity can only be realised within a functioning environment.”
The term Nitrogen Fertiliser Use Efficiency (NfUE) is used to describe the recovery of Nitrogen fertiliser applied to the crop.
Alli Grundy explains “NfUE gives growers a clear picture of the impact of fertiliser choice on production efficiency and can highlight where potential environmental concerns might result. There is good evidence that the higher the quality of fertiliser, the higher the NfUE achieved, especially with high grade Ammonium Nitrate such as Nitram (34.5%N).
THE VALUE OF IMPROVING NfUE
NfUE works by removing all other Nitrogen sources from the overall NUE calculation to show how the bought-in fertiliser is performing. Efficiency values for crops typically range between 40% to 70% (see table) but it is clear that better quality AN based solid fertilisers are at the top end of this scale whereas urea-based products, liquids and blends tend to be at the lower end.
TABLE 1. TYPICAL NfUE VALUES BY CROP
For example, in milling wheat trials carried out by arable research contractors Armstrong Ltd, applying zero N to trial plots produced 4.2 t/ha whereas applying the optimum N rate of 254kg N/ha produced 10.4t/ha.
The N offtake (N in the crop at harvest), was 68kg N/ha for the crop with no fertiliser added and 257kg N/ha where the optimum amount was applied giving a final equation of 257 – 68 divided by 254 which equals 74%.”
The season plays an enormous part in the recovery of nutrients, however, and the decisions we make during the application period, all affect the final recovery rate.
In reviewing our own trials and ADAS literature to set the correct parameters for the CF N-Calculator, we’re seeing NfUEs of around 70% for winter wheat but many factors can affect this with product choice being important.”