Assessing the benefits and wider costs of different N fertilisers for grassland agriculture

Alison Carswell, Rory Shaw, John Hunt, Antonio Rafael Sánchez-Rodríguez, Karen Saunders, Joseph Cotton, Paul W. Hill, Dave R. Chadwick, Davey L. Jones, Tom H. Misselbrook

Research output: Contribution to journalArticlepeer-review

16 Citations (Web of Science)


Fertiliser nitrogen (N) is essential for maintaining agronomic outputs for our growing population. However, the societal, economic and environmental impacts of excess reactive N from fertiliser is rarely assessed. Here the agronomic, economic and environmental efficacy of three N-fertiliser sources, ammonium-nitrate (AN), urea (U), and inhibited-urea (IU; with NPBT) were evaluated at two grassland sites. Dry matter yield and herbage quality were measured at each silage-cut. Additionally, NH 3 -N and N 2 O-N losses were measured and used to calculate the effective N source cost and externality costs, which account for associated environmental and societal impacts. We found no effect of different N sources on yield or herbage quality. However, NH 3 -N emissions were significantly reduced under the IU treatment, by 48–65%. No significant differences in cumulative N 2 O emissions were observed. Incorporating externality costs increased fertiliser prices by 1.23–2.36, 6.51–16.4, and 3.17–4.17 times the original cost, for AN, U and IU, respectively, transforming U from the cheapest, to the most expensive of the N sources examined. However, with no apparent yield differences between N-fertiliser sources there is no economic incentive for the land-manager to use the more environmentally and socially acceptable option, unless externality costs are incorporated into fertiliser prices at the point of sale.

Original languageEnglish
Pages (from-to)625-639
Number of pages15
JournalArchives of Agronomy and Soil Science
Issue number5
Publication statusPublished - 16 Apr 2019


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