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Three-quarters of the Nitrogen put into Irish soils is not utilised, costing farmers millions and damaging the environment - but there are ways to cut the losses



Photo: Roger Jones

Photo: Roger Jones

Photo: Roger Jones

It might make for unpleasant reading, but millions of euro worth of nitrogen is being wasted on Irish farms each year.

With just a 20pc of soil in optimum condition to utilise the nitrogen applied to it, farmers are seeing this valuable input literally wash down the drain or escape into the atmosphere.

However, with pressure ramping up on agriculture to raise its game on emissions, cleaning up our act in this area is can no longer be kicked down the road.

As Teagasc researcher David Wall explained in stark terms to farmers at the National Sheep Conference last week, "if we maintain our stock, which are the lifeblood of our rural economy and farming systems, we have to tackle the other side of the pie - the other 40pc of agri emissions that come from nitrogen by and large".

Despite shooting up in recent years on the back of dairy expansion, nitrogen use on Irish farms had been static since the 1980s.

However, over the same period sales of other critical nutrients such as P and K and lime fell dramatically.

"An awful lot of damage was done to soil fertility on farms over that period," Wall told farmers.

Looking at how much nitrogen is actually utilised on Irish farms, he said: "A lot of people wouldn't believe me if I said that it's probably in the region of just 25pc across all grassland."

So just a quarter of the nitrogen we put into the system is actually recovered in an end product - milk or meat.

Such a shocking statistic demands immediate action, Wall stressed, pointing out that improving nitrogen efficiency would keep more money in farmers' pockets, grow more grass and reduce emissions.

A reduction in N fertiliser of 10kg/ha by implementing key changes on farm will reduce farm emissions by 1pc and improve income by €10/ha.


According to Wall, lime is where every farmer should start, describing it as the "foundation of soil fertility" and critical to making nutrients such as nitrogen work as they should.

"We have acidic soils and high rainfall, particularly in the west of the country," he said.


There is a shortfall of lime application

There is a shortfall of lime application

There is a shortfall of lime application

Maintaining grassland soils within the optimum pH range of 6.3 creates a suitable environment for micro-organisms and earthworms to thrive and break down plant residues, animal manures and organic matter. This helps to release stored soil nutrients such as N, P, K, sulphur (S) and micro-nutrients for plant uptake.

For example, grassland soils receiving regular lime applications have been shown to release up to 80kg/ha additional N compared to soils with low soil pH.

"If we compare nitrogen to fuel in a car," Wall explained, "lime, P and K are like engine oil.

"We cannot utilise the fuel without having the fertility right."

P and K

Optimising soil P and K fertility across the field is important on all farms that use moderate to high levels of N fertiliser.

"Where soil P and K fertiliser is low the efficiency with which grass can uptake and recover fertiliser N is drastically reduced," Wall said.

He added that in soils low in P, more than 15pc of the N applied is potentially wasted as it is not recovered by the grassland.

Low-emissions slurry spreading

Another important part of the nitrogen use puzzle is slurry and manure management, Wall said, stressing that farmers need to recover more nutrients out of this vital resource.

He said the answer lies in low-emission spreading, which maximises the nitrogen use efficiency of slurry.


The umbilical slurry spreading charge rate is guided at €150.00/hour plus VAT.

The umbilical slurry spreading charge rate is guided at €150.00/hour plus VAT.

The umbilical slurry spreading charge rate is guided at €150.00/hour plus VAT.

"The problem with the splash plate is basically a surface area issue. Farmers are covering the whole surface with slurry," he said. "On a dry and sunny day the sun bakes off the nitrogen and it goes up in the air. In the worst-case scenario, 90-95pc of the nitrogen is gone. We can do better.

"Using either the trailing shoe or dribble bar improves the efficiency of N within slurry by around 3 units of N per 1,000 gal compared to using splash-plate."

Soil Test

Soil testing is a no-brainer, according to Wall. He warned that if farmers don't have a soil analysis for their whole farm they were "shooting in the dark".

"A soil test is cheap as chips. It lasts for four years and costs about €1/ac. If we think about a tonne of CAN fertiliser at €250/t or 18.6.12 at upwards of €400…"

He said it doesn't make sense that farmers would make a decision to spread fertiliser at €400/t without being prepared to spend €1 to have the information from a soil test.

Protected urea is a cost-effective way to boost N use efficiency

When selecting which nitrogen fertiliser to use, the common practice until recently on Irish farms was to use urea in the spring and CAN in the summer.

"Farmers have been using urea in wet weather and converting over to CAN in dryer conditions," Teagasc researcher David Wall explained. Despite these efforts the system has not fully prevented losses both in terms of leaching and emissions to the atmosphere, Wall said, noting that farmers now need to look at another nitrogen fertiliser option.


They don't come cheap, but fertiliser programmes to address soil fertility issues are not complicated

They don't come cheap, but fertiliser programmes to address soil fertility issues are not complicated

They don't come cheap, but fertiliser programmes to address soil fertility issues are not complicated

Recent research at Teagasc Johnstown Castle found that protected urea had 71pc lower greenhouse gas emissions than CAN and 79pc lower ammonia-N emissions than regular urea.

Protected urea has the same granule as normal urea - the only difference is that a protection in the form of an inhibitor has been added to the granule. This reduces ammonia-N gas emissions from the urea, which means that more of the fertiliser N is available for grass growth. 

Trails found that protected urea produced the same amount of grass as CAN and has higher N use efficiency than normal urea due to reduced ammonia emissions. Suitable Protected urea is also suitable for spreading throughout the whole grazing season. 

The Government wants farmers to dramatically increase the use of the product in the coming years. Wall explained that at present protected urea comes as straight N (46pc) or in a compound with potash and/or sulphur.

"This is the second big year out of the blocks for protected urea," he said, conceding that a lot of merchants didn't have a plentiful supply of the product last year. "They had it in the spring and then it was gone. It was a test year." 

However, he also assured farmers that from his communications with the fertiliser companies, it is his understanding that it will be available through the entirety of this year. "There is straight nitrogen 46pc N, so farmers don't need to bring as much home with them. They need to remember they are bringing more nitrogen home with each load," he said.

"The product does what it says on the tin. It retains nitrogen in the soil for the plant uptake." Protected urea costs around €0.95 per N/kg; CAN is costing around €1.05 per N/kg based on current fertiliser N prices.

Indo Farming