Temperate grassland yields and nitrogen uptake are influenced by fertilizer nitrogen source

Core Ideas
CAN is a widely used form of straight N in Western Europe.
Urea+NBPT consistently delivered equal yields and N uptake compared with CAN.
CAN had higher N uptake than urea in 2 of 6 site-years, but yields were not different.
NBPT increased the N uptake of urea in 2 of 6 site-years but had no effect on yield.
Urea+DCD had lower yield and N uptake than CAN in 3 and 4 of 6 site-years, respectively.
In temperate grasslands, N source influences greenhouse gas emissions. Nitrification and urea hydrolysis inhibitors can reduce these losses. The objective of this study was to evaluate the impact of N source, urease inhibitors, and nitrification inhibitors on temperate grassland yields and N uptake. Experiments were conducted at three locations over 2 years (6 site-years) on the island of Ireland, covering a range of soils and climatic conditions. Results showed that calcium ammonium nitrate (CAN), urea+N-(n-butyl) thiophosphoric triamide (NBPT), urea+NBPT+dicyandiamide (DCD), and urea had equal annual dry matter yield. Urea+DCD had lower dry matter yield than CAN for 3 site-years. Calcium ammonium nitrate and urea+NBPT consistently had the same N uptake, urea+DCD had lower N uptake than CAN in 4 of 6 site-years, urea had lower N uptake than CAN in 2 site-years, and urea+NBPT+DCD had lower N uptake than CAN in 1 site-year. Urea+NBPT is a cost-effective alternative to CAN, which is consistently equal in terms of yield and N uptake in temperate grassland.