You can be forgiven if you are feeling somewhat confused by the current nitrogen scene. Some years ago life was very simple with only limited options available but today the choice is a whole lot more complicated.
Not long ago the choice for nitrogen source was mainly one of solid ammonium nitrate (AN) or liquid urea ammonium nitrate (UAN). Whilst the other options of urea, ammonium sulphate, calcium nitrate (CN) or calcium ammonium nitrate (CAN) were all available, they were largely dismissed through reasons such as poor quality, niche markets or due to their relative high pricing. Today improvements in quality, abundant supply and a need to spread accurately at wider bout widths (>24m) has brought these back into the frame. Add into this mix inhibitors, sulphur, precision application and NPKS options and the picture gets a whole lot more complicated.
So how do we unravel the nitrogen tangle?
First and foremost is to consider your priorities, which could be economics / profitability, environmental performance and risk management. With profitability and risk mitigation driven mainly by consistent yield attainment, but in addition the use of assets such as machinery and labour, then one group separates itself out.
By way of yield attainment then nitrates are recognised as the best performers, with Calcium Nitrate topping the list due to its 100% nitrate form. However, on the classic broad acre crops (wheat, oilseed) its value prohibits widespread use accept as an option for achieving the milling premium.
The nitrate component is the key as this is the preferred, plant available nitrogen form, so CAN, AN and UAN fall into line giving the most consistent and reliable economic performance with a current return on investing in nitrate nitrogen of £3.77 for wheat and £3.61 for oilseed per £1 investment. This reliability is born out when very large data sets are analysed. The number of statistically significant results favouring those where nitrates outperform urea.
Are accuracy and efficiency your priorities? - If so nitrates may be the best option
If accuracy is your number one focus and you are operating at 24, 32 or 36m then the choice is straightforward, you either go with a high quality, strong granulated product (e.g. YaraBela Axan or Extran) or for ultimate precision - liquids ( e.g. Chafer Nuram 37), where headland and overlaps can be managed with ease.
If you are looking towards efficiency through optimising resources (machines, labour and land) then liquid UAN becomes the preferred option. Liquids can be applied to the highest level of accuracy at the very widest tramlines such as 48m. It is worth calculating out the uncropped area in the form of tramlines and seeing what extra farmed area you have!
So where do the other forms fit in to the discussion. Urea has improved in its quality and become much more abundant as North Africa and China production levels have increased. Indeed Yara have made further investments in its European production facilities, increasing supply of nitrate and urea products. The focus and investment has been directed towards granulated, nitrogen plus sulphur grades as the demand continues to grow for these.
If you are happy with some risk then opting for granulated urea plus sulphur as part of a system can be a useful alternative.
What is your attitude to risk ? - If you are prepared to accept some risk then urea may be an option
It was mentioned earlier that the third element to consider was attitude to risk and this is exactly the predicament with urea products. It is widely accepted that urea will lose more than 20% of its nitrogen in the form of ammonia following application as compared to around 3% with ammonium nitrate. Such a loss immediately introduces risk as it all depends on where the ammonia nitrogen ends up, in the crop/soil or atmosphere. Clearly if it is the latter then this will add nothing towards crop productivity, reducing yield and quality, but plenty towards an environmental impact.
The urease inhibitors have been introduced as a way of reducing this loss and Yara’s own research has shown how effective they are at this, but in doing this they of course inhibit the exact process that is required to turn unavailable urea nitrogen into available nitrate nitrogen – another introduction of risk into the nitrogen cycle. Such inhibitors also add cost narrowing the price gap between the various options. Positive yield responses with the addition of inhibitors is very sporadic with no clear trend, especially when operating at or below the nitrogen optimum which is most situations.
Is the carbon footprint of nitrogen important to you?
There is also the growing issue of carbon footprints, especially if you are in a value chain that is focused on this. Such a priority leads you to sourcing nitrogen products that are produced in very energy efficient, abated, western European production facilities.
Having highlighted a few issues, there is one that should be the goal for us all, improved Nitrogen Use Efficiency (NUE). Good NUE comes from available nitrogen forms applied in multiple application, coincident with crop demand, you can decide how that might be best achieved.