Enhanced efficiency fertilisers reduce nitrous oxide emissions and improve fertiliser 15N recovery in a Southern Australian pasture

Helen Suter; Shu Kee Lam; Charlie Walker; Deli Chen

doi:10.1016/j.scitotenv.2019.134147

Enhanced efficiency fertilisers reduce nitrous oxide emissions and improve fertiliser ¹⁵N recovery in a Southern Australian pasture

Sci Total Environ. 2020 Jan 10:699:134147. doi: 10.1016/j.scitotenv.2019.134147. Epub 2019 Aug 27.

Authors

Helen Suter¹, Shu Kee Lam², Charlie Walker³, Deli Chen²

Affiliations

¹ School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia. Electronic address: helencs@unimelb.edu.au.
² School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia.
³ Incitec Pivot Fertilisers, Seabreeze Parade, North Shore, Victoria 3214, Australia.

PMID: 31629314
DOI: 10.1016/j.scitotenv.2019.134147

Abstract

The effects of reducing nitrogen (N) rates or using enhanced efficiency fertilisers (EEFs) (i.e. urease and nitrification inhibitors, and controlled release fertilisers) on nitrous oxide (N₂O) emissions and nitrogen use efficiency (NUE) are not well understood in temperate, rainfed pastures. A field experiment on rainfed ryegrass pasture in southern Australia examined the effect of granular urea N rate (0, 250 and 420 kg N ha^-1 over 6 months) and EEF use (at 250 kg N ha^-1 with NBPT, DMPP, or polymer coating (PCU)) on N₂O emissions, NUE and fertiliser N recovery (using ¹⁵N techniques). Cumulative net-N₂O emissions increased with N rate from 308 g N₂O-N ha^-1 (250 kg N ha^-1) to 514 g N₂O-N ha^-1 (420 kg N ha^-1). Using EEFs reduced N₂O emissions by 22% (NBPT), 44% (DMPP) and 56% (PCU) compared to urea. The emission factor (EF) (kg net N₂O-N per kg N applied) was 0.12 for both N rates (250 and 420 kg N ha^-1) but reduced with the EEFs to 0.10 (NBPT) and 0.07 (DMPP and PCU) compared to urea. EEF use had no significant impact on biomass or apparent NUE but led to a greater recovery of N in the soil after one month (44.8% (DMPP) and 45.9% (NBPT) compared to urea (33.7%)). Within one month 42% of the N applied as urea (U50) was lost from the plant-soil system, which was reduced with DMPP (32% loss) and NBPT (33% loss). After six months, 52% (U50) to 59% (U84) of the urea N applied was lost. The positive effect of the EEFs on N₂O emissions, and the increased recovery of N in the soil-plant system with the EEFs over one month indicates they could provide longer term benefits though soil N storage, and could be applied at lower N rates to achieve NUE benefit.

Keywords: Nitrification inhibitor; Nitrous oxide; Pasture productivity; Polymer coated fertiliser; Urease inhibitor.