Abstract
ABSTRACT
Context. Agricultural soils are a major source of emissions of the greenhouse gas nitrous oxide
(N2O). Aim. Quantify direct N2O emissions from Australian agricultural production systems
receiving nitrogen (N) inputs from synthetic and organic fertilisers, crop residues, urine and
dung. Method. A meta-analysis of N2O emissions from Australian agriculture (2003–2021)
identified 394 valid emission factors (EFs), including 102 EFs with enhanced efficiency fertilisers
(EEFs). Key results. The average EF from all N sources (excluding EEFs) was 0.57%. Industry-based
EFs for synthetic N fertiliser (excluding EEFs) ranged from 0.17% (non-irrigated pasture) to 1.77%
(sugar cane), with an average Australia-wide EF of 0.70%. Emission factors were independent of
topsoil organic carbon content, bulk density and pH. The revised EF for the non-irrigated cropping
(grains) industry is now 0.41%; however, geographically-defined EFs are recommended. Urea was
the most common N source with an average EF of 0.72% compared to urine (0.20%), dung (0.06%) and
organo-mineral mixtures (0.26%). The EF for synthetic N fertilisers in rainfed environments increased
by 0.16% for every 100 mm over 300 mm mean annual rainfall. For each additional 50 kg N ha−1 of
synthetic fertiliser, EFs increased by 0.13%, 0.31% and 0.38% for the horticulture, irrigated and high
rainfall non-irrigated cropping industries, respectively. The use of 3,4 dimethylpyrazole-phosphate
(DMPP) produced significant reductions in EFs of 55%, 80% and 84% for the horticulture, nonirrigated and irrigated cropping industries, respectively. Conclusions and implications. Incorporation
of the revised EFs into the 2020 National Greenhouse Accounts (NGA) produced a 12% increase in
direct N2O emissions from the application of synthetic N fertilisers. The lack of country-specific
crop residue decomposition data is a major deficiency in the NGA.
Context. Agricultural soils are a major source of emissions of the greenhouse gas nitrous oxide
(N2O). Aim. Quantify direct N2O emissions from Australian agricultural production systems
receiving nitrogen (N) inputs from synthetic and organic fertilisers, crop residues, urine and
dung. Method. A meta-analysis of N2O emissions from Australian agriculture (2003–2021)
identified 394 valid emission factors (EFs), including 102 EFs with enhanced efficiency fertilisers
(EEFs). Key results. The average EF from all N sources (excluding EEFs) was 0.57%. Industry-based
EFs for synthetic N fertiliser (excluding EEFs) ranged from 0.17% (non-irrigated pasture) to 1.77%
(sugar cane), with an average Australia-wide EF of 0.70%. Emission factors were independent of
topsoil organic carbon content, bulk density and pH. The revised EF for the non-irrigated cropping
(grains) industry is now 0.41%; however, geographically-defined EFs are recommended. Urea was
the most common N source with an average EF of 0.72% compared to urine (0.20%), dung (0.06%) and
organo-mineral mixtures (0.26%). The EF for synthetic N fertilisers in rainfed environments increased
by 0.16% for every 100 mm over 300 mm mean annual rainfall. For each additional 50 kg N ha−1 of
synthetic fertiliser, EFs increased by 0.13%, 0.31% and 0.38% for the horticulture, irrigated and high
rainfall non-irrigated cropping industries, respectively. The use of 3,4 dimethylpyrazole-phosphate
(DMPP) produced significant reductions in EFs of 55%, 80% and 84% for the horticulture, nonirrigated and irrigated cropping industries, respectively. Conclusions and implications. Incorporation
of the revised EFs into the 2020 National Greenhouse Accounts (NGA) produced a 12% increase in
direct N2O emissions from the application of synthetic N fertilisers. The lack of country-specific
crop residue decomposition data is a major deficiency in the NGA.
| Original language | English |
|---|---|
| Article number | SR23070 |
| Journal | Soil Research |
| Volume | 62 |
| Issue number | 1 |
| DOIs | |
| Publication status | E-pub ahead of print - 27 Nov 2023 |
