Teagasc research has dismissed concerns around residues associated with protected urea.

A five-year study has found that there was no impact of urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), incorporated into protected urea fertiliser, on the structure and abundance of soil bacterial and fungal communities.

The Johnstown Castle research further showed that the microbial communities involved in nitrogen cycling and nutrient transformation remained unchanged with the use of the urease inhibitor.

“Fertiliser application, either via calcium ammonium nitrate (CAN) or urea, did change the fungal community structure, but the bacterial community structure in fertilised plots was not significantly different from the unfertilised plots,” Teagasc stated.

Concerns around the use of the urease inhibitor were raised by the fertiliser industry, and have been a factor in the slow uptake of protected urea by farmers.

“This study shows that nitrogen fertilisation is a major driver of fungal community change, while the urease inhibitors found in protected urea have no significant effect on the fungal and bacterial communities,” said Teagasc scientist Aoife Duff.

“Where inorganic nitrogen fertilisers are being applied to meet plant growth requirements, protected urea represents a good option for reducing nitrogen losses from the system, which result in a financial loss to the farmer and are potentially damaging to the environment,” added fellow researcher Fiona Brennan.

The increased use of protected urea is a key part in agriculture’s battle to reduce greenhouse gas emissions.

Previous research from Teagasc Johnstown Castle has demonstrated that switching from CAN to protected urea fertiliser reduced nitrous oxide emission factors by 71% and reduced ammonia volatilisation by 78.5%, while maintaining grass yields.