Is it time to go liquid?

Though not for everyone, nitrogen applied through a sprayer can offer benefits compared to solid products. Shay Phelan, Teagasc Crops Specialist, and John Pettit, Tillage Advisor, look at the pros and cons as part of this article in Today’s Farm.

As spreader technology improved in recent years, many tillage farmers moved to use unprotected urea on tillage farms. They could achieve relatively good spread patterns and achieve savings as it was cheaper per kg of nitrogen. With the exit of unprotected urea from the market in 2026, farmers are facing into a new era of crop nutrition.

While Calcium Ammonium Nitrate (CAN) will remain the choice for many tillage farmers, protected urea and liquid nitrogen in the form of UAN (Urea, Ammonium, Nitrogen) will also be considered. But which is the best from a tillage point of view? To establish which is the best option for your own farm consider:

1). Crop performance

Work carried out by Teagasc Oak Park scientists shows that there is no difference between the options in terms of crop performance either in yield terms, or in the case of malting barley, protein percentage. When each of the three products is applied correctly there should be no real difference between them in terms of crop performance.

2). Cost

Urea tended to be about 80% of the cost of CAN per kilo of nitrogen. The addition of a urease inhibitor e.g. NBPT, almost brings protected urea in line with the cost of CAN. UAN products generally tend to be slightly more expensive than CAN.

3). Spread performance

Most farmers have worked with CAN and generally know its limitations in terms of spread widths etc. Many have tried protected urea over the last few years. It can be spread up to 24 metres quite accurately with appropriate settings and vein positioning. However, because of the bulk density it is extremely difficult to spread at 30 metres. This is especially the case in windy conditions.

UAN can literally be spread the width of the boom on the sprayer. So spreader performance shouldn’t be an issue once the correct nozzles and setup are used. There is more accuracy on headlands with little or no product being spread into hedgerows. Even with the most accurate headland management and GPS systems on spreaders, they can still deposit a certain amount of solid fertiliser into hedgerows.

There can be an edge effect on the crop too where the outside metre gets less than optimum fertiliser in an effort to prevent fertiliser being spread into the field margins.

4). Accuracy

Distribution patterns for fertiliser spreaders are calculated in the factories of the machine’s manufacturer and they typically design a pattern of overlap that deposits as much fertiliser as is necessary within the spread pattern for a particular product.

This obviously depends on the quality of the product being spread, the volume, and the width of the tramline. These are generally quite forgiving and there is usually some tolerance for over- or under-spreading.

With liquid fertiliser there is little or no room for over or underlapping. Boom widths have to be accurately measured otherwise you could be applying double, or zero, of the rate at the edge of the boom. This will result in striping of the crop and yield loss.

5). Convenience

One of the selling points of using urea was that you could spread the same area with a smaller amount of fertiliser. Since you were spreading a 46% urea product versus a 27% product in CAN, the application rate in kg/ha was lower with urea. This meant that you could cover a larger area quicker. This was especially beneficial when having to travel some distance to different fields.

Similarly, with protected urea you have a higher percentage nitrogen product than CAN. This lends itself to greater output per hour or day. In the case of liquid fertilisers, you are applying a similar percentage nitrogen product to CAN. So, the output per hour or day would be less than the urea. ESB or telegraph poles will slow down the operation.

You may have more days suitable for application with liquid fertiliser. Another advantage is that you can always return any unused product into a storage tank; this is not as easy in the case of solid fertiliser.

6). Weather

Wind is your biggest enemy with solid fertilisers, especially with low bulk density products like urea (protected and unprotected). CAN is slightly more forgiving in windy conditions while applying liquid is the most forgiving.

All fertilisers can be spread on wet crops or in damp conditions. However, don’t apply liquid onto wet crops that are going to be dry within a few hours, e.g. on a dewy morning.

In dry conditions in the spring, both CAN and protected urea will offer some protection from ammonia losses. The urea part of the UAN can potentially be lost in very dry conditions in a similar way to the solid urea fertilisers in the past.

There are certainly options for tillage farmers in the type of nitrogen they use. It is certainly worthwhile sitting down with your advisor to see which option works best on your farm. Don’t just focus on cost. There are many other considerations including crop performance, convenience and, more importantly going forward, the environmental impact.

Positive experience

Co. Wicklow tillage and dairy farmer Tom Short has been using liquid nitrogen for five seasons. Tom grows winter and spring cereals, beans, and oilseed rape as well as grass for the dairy herd.

“Our motivation for the move to liquid nitrogen was achieving an even spread pattern right out to the headland,” says Tom. “It’s hard to avoid losing some solid fertiliser to hedgerows or field margins. This is something we have to prevent.”

Tom had moved to 30 metre tramlines. “Spreading solid fertiliser to that distance is difficult unless the weather is calm. Moving to liquid nitrogen, which is less susceptible to wind, has increased the number of days on which we can apply nitrogen, helping to spread the workload.

“Auto steer on the tractor when drilling the crop, and section control on the sprayer, are absolute necessities to avoid the overlap or non-application of liquid fertiliser.”

Tom says liquid nitrogen is marginally more expensive than granular nitrogen. The work rate with liquid fertiliser is also somewhat slower taking 20% longer to apply a given quantity of nitrogen.

A set of streamer nozzles had to be purchased to facilitate the application of liquid fertiliser through the sprayer. And even though liquid nitrogen storage tanks were supplied free of charge, there was a considerable investment in concrete-bunded tanks in the farmyard to ensure potential spillages are retained.

“On balance, liquid nitrogen certainly suits our system,” concludes Tom. “Applied accurately, it benefits the farmer, the crop and the environment.”

For more insights, view the full edition of Today’s Farm here.