Enhanced urea fertiliser offers 5% extra yield

An enhanced urea fertiliser that contains two different urease inhibitors promises to deliver yields equivalent to crops grown using ammonium nitrate.

Urease inhibitors can have a valuable role in reducing N losses as ammonia via volatilisation, which research suggests can average 20% from straight urea.

This not only represents wasted nitrogen, but ammonia also affects air quality and the UK government is committed to a 16% reduction (below 2005 levels) in emissions by 2030. 

See also: A round-up of enhanced urea fertilisers and additives

One way to reduce losses from urea fertiliser is by the use of urease inhibitors. There are several enhanced urea fertilisers on the market and they typically contain one of two inhibitors, NBPT or 2-NPT.

However as Basf campaign manager Jane Kitchen points out, there are many types of urease enzyme in soils and the inhibitors do not stop all of them.

So by having two, Limus benefits from a combined effect, achieving a greater reduction in ammonia losses. It contains NBPT plus a brand new inhibitor developed by the company – NPPT.

She points to Basf trials showing up to 98% reduction in ammonia, and separate Adas trials with a 5% increase in yield across a range of crops when using Limus instead of conventional urea.

“It delivered the same level of crop performance as when using ammonium nitrate,” she says.

How do urease inhibitors work?

Nitrogen in standard urea fertiliser has to undergo conversion to the ammonium form before plants can take it up via their roots.

This process is carried out by urease enzymes from soil microbes.

However, this process can happen rapidly under certain conditions, such as when temperatures are higher, on lighter soils and on alkaline soils (pH>7.5).

This can lead to significant nitrogen losses through volatilisation as ammonia.

The Basf product works by binding with the urease enzymes, thereby slowing down the process.

Limus is available through three suppliers: Bartholomews, Cofco and Thomas Bell.

A liquid version for use with liquid fertiliser is being trialled this season on selected farms.

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