Urease inhibitors increase viability of urea fertilisers

Using urease inhibitors could help growers in Northern Ireland make the use of urea fertilisers more viable, an agronomists conference was told.

“Although urea has high nitrogen content and is the cheapest source in terms of price per unit of N, there are significant losses from volatilisation after application,” explained Catherine Watson, of the Agri-Food and Biosciences Institute (AFBI).

“You see particularly high losses when it is applied on wet soils, which then dry out post application. Lighter soil types are more conducive to high nitrogen losses,” she added.

In Northern Ireland, the main sources of nitrogen calcium ammonium nitrate and farm yard manure, with urea and liquid solutions not widely used. Ammonium nitrate remains unavailable to growers.

Speaking at the Agronomy and Business Management Conference for Cereal Growers at the College of Agriculture, Food and Rural Enterprise (CAFRE), Greenmount Campus, Antrim, Dr Watson said the use of urease inhibitors would reduce nitrogen losses by slowing the process of hydrolysis, which produces ammonia. “Therefore yield responses can be improved.”

Calcium ammonium nitrate prices are higher than urea therefore a more efficient urea product could appeal to cereal growers in Northern Ireland, where wet conditions are often experienced.

The urease inhibitor Agrotain, which was developed in the USA, is either used to coat the granules or added to the urea melt during manufacture.

“Trials have shown that untreated urea retains just 74% of N after volatilisation,” said Ms Watson. “Agrotain treated urea is much better at 93.4%, which is comparable with ammonium nitrate at 96.3%.”

There are also environmental benefits to using urea, with urea products producing considerably less nitrous oxide after application than that of ammonium nitrate.

“Nitrous oxide is a particularly potent greenhouse gas, around 298 times greater than carbon dioxide,” said Dr Watson.

“Amended urea, using Agrotain, not only reduces ammonia losses into the environment but also reduces greenhouse gas emissions, particularly under wet conditions.”

The cost of amending urea with Agrotain is around US$50/tonne, which equates to £70/tonne of nitrogen.

“Even with recent price rises for urea there is still some economic benefit of using amended urea rather than calcium ammonium nitrate,” said Dr Watson. “Although the higher lime costs associated with using urea must also be considered.”

Despite its advantages, Dr Watson warned that the product could not always be considered a replacement for ammonium nitrate-derived fertiliser.

“Urea will never be as efficient as ammonium nitrate, but with the increased efficiency that urease inhibitors can provide it gives growers a viable alternative.”

Agrotain treated urea is being marketed by Koch fertilisers and is available this season under the product name KAN.

• Read more from the Agronomy and Business Management Conference for Cereal Growers.

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