Farm Table says:
What is the problem?
The application of nitrogen (N) fertilizers to pasture is known to increase nitrous oxide (N2O) emissions.There is currently little information available on emissions from N fertilized dairy pastures in Australia.
What did the research involve?
Field experiments (five treatments by five replicates) were conducted at two sites in south-west Victoria with contrasting drainage characteristics.
• urea coated with dicyandiamide (DCD)
• Urea coated with 3,4-dimethyl pyrazole phosphate (DMPP)
• urea coated with N-(n-butyl) thiophosphoric triamide (nBPT).
The urea+DCD treatment was replaced with urea ammonium nitrate (UAN) in Years 2 and 3.
The N treatments were applied at the start of the growing season and again after every second harvest.
Pasture production was measured for three years and N2O emissions were measured for two years.
What were the key findings?
• Pasture responded to the application of N fertilizer at both sites every year.
• There were no differences in pasture production between the urea, urea plus inhibitor coatings or the UAN treatments.
• The use of a nitrification inhibitor reduced emissions by 30 to 75%, with the magnitude of the reduction influenced by soil water content around the time of N application.
• The urease inhibitor had no effect on N2O emissions
The use of nitrification inhibitors was effective in reducing N2O emissions, when conditions conducive to emission losses were high, such as when WFPS was above 70%. Overall, as the total loss of N as N2O was small, a production response to nitrification inhibitor use is unlikely.