1. A field study on the impact
of the nitrification inhibitor
DMPP on N2O emissions
from a pasture in south
western Victoria
Helen Suter, Humaira Sultana
and Deli Chen
(The University of Melbourne)
Rohan Davies and Matthew Mahoney
(Incitec Pivot)

2. Nitrification and inhibitors
Urea
N2O
hydrolysis
denitrification
nitrification
NH4 + NO3- N2
(eg. Nitrosomonas)
N2O
Nitrification inhibitor eg. Dimethylpyrazole phosphate (DMPP)

3. Experimental methodology
Treatments
• Control
• Urea
• Urea with Entec® = Urea + DMPP ( Dimethyl pyrazole phosphate)
5 replicates/treatment

4. Experimental methodology
• Location : Murroon, south west Victoria
• Average annual rainfall : 660 mm
• Pasture : 2 year old ryegrass seed pasture
• Soil : duplex, silty loam topsoil, pHW 5.5
• Grazing : sheep grazing (prior to trial)
• Plot size : 2 m x 1 m
• Application rate: 40 kg N/ha Source: Google maps
• Start date: 12 April 2010
• End date: 23 December 2010
• Fertilisation events: 7
• Gas collection: manual chambers (23 x 20 cm)

5. Experimental methodology : Data Collection
o Gas – N2O, CO2, CH4
• 3 samples (0, 30, 60 mins)/chamber
• weekly and event driven
• analysed in lab
o Soil
• fortnightly
• NH4+ and NO3-
o Biomass production and N content
• monthly
o Additional data
• climate data
• soil moisture and temperature

6. Results: Daily N2O emissions (April-Oct)
45
control fertiliser application at 40 kg N/ha
40 urea
DMPP
35
Calculated daily N2O (g/ha)
30
25
20 site waterlogged, no sampling
15
10
5
0

7. 35
control fertiliser application at 40 kg N/ha
30
urea
DMPP
25
Calculated daily N 2O (g/ha)
20
site waterlogged, no sampling
Results: 15
Daily N2O
10
emissions and
rainfall (April-Oct) 5
0
40
35
30
Rainfall (mm)
25
20
15
10
5
0
(Total rainfall 522 mm)

8. 35
control fertiliser application at 40 kg N/ha
30
urea
DMPP
25
Calculated daily N 2O (g/ha)
20
site waterlogged, no sampling
Results: 15
Daily N2O
10
emissions and
daily mean 5
maximum
0
temperature
(April-Oct)
30
25
Temperature (oC)
20
15
10
5
0

9. Results: Cumulative Net-N2O emissions
450
400
350 Urea
fertiliser application at 40 kg N/ha
Calculated cumulative Net-N2O (g/ha)
300 DMPP
250
200 73%
reduction
150
100
50
0

10. Results : soil nitrate levels
18
16
14
12 Control
Nitrate -N (kg/ha)
DMPP
10
Urea
8
6
4
2
0

11. 18
16
14
12 Control
Nitrate -N (kg/ha)
DMPP
10
Urea
8
Results : soil 6
nitrate levels and
4
potential for
2
leaching loss
0
40
35
30
Rainfall (mm)
25
20
15
10
5
0

12. 18
16
14
12 Control
Nitrate -N (kg/ha)
DMPP
10
Urea
8
Results : soil 6
nitrate levels and
4
potential for
2
leaching loss
0
40
Potential for leaching 35
losses reduced with DMPP 30
Rainfall (mm)
25
20
15
10
5
0

13. Results : Dry Matter (DM) production (kg/ha)
Cumulative
Treatment 10-May 7-Jun* 19-Jul 3-Sep 27-Sep 21-Oct (240 kg N
applied)
Control 428 ± 68 106 ± 24 232 ± 45 259 ± 35 256 ± 29 454 ± 46 1736
Urea 699 ± 70 159 ± 9 569 ± 11 876 ± 82 818 ± 33 1027 ± 41 4149
Urea + DMPP 748 ± 97 207 ± 36 618 ± 71 949 ± 74 754 ± 60 1030 ± 78 4307
% increase in
net DM with 18 89 14 12 -11 1 6
DMPP
(Value is average of 5 reps ± standard error)
* 7 June sampling comes 2 months after fertilisation on 12 April

14. Results : Dry Matter (DM) production (kg/ha)
Cumulative
Treatment 10-May 7-Jun* 19-Jul 3-Sep 27-Sep 21-Oct (240 kg N
applied)
Control 428 ± 68 106 ± 24 232 ± 45 259 ± 35 256 ± 29 454 ± 46 1736
Urea 699 ± 70 159 ± 9 569 ± 11 876 ± 82 818 ± 33 1027 ± 41 4149
Urea + DMPP 748 ± 97 207 ± 36 618 ± 71 949 ± 74 754 ± 60 1030 ± 78 4307
% increase in
net DM with 18 89 14 12 -11 1 6
DMPP
* 7 June sampling comes 2 months after fertilisation on 12 April

15. Conclusions : DMPP impact on N2O emissions from a
pasture
Compared to urea, DMPP :
• delayed formation of NO3--N at some times of the year with greatest impact
during high rainfall periods
– April, June, August
• reduced Net-N2O emissions:
– over a 6 month period by 73%
– at particular times of the year (high temp/rainfall) but not always
• increased the longevity of supply of N for plant growth for 60 days leading to
an 87% increase in DM production (June sampling) compared to urea

16. Acknowledgements
Debra Turner, Yuntong Liu, Xing Chen, Robert
Edis, David Hopkins, Peter and Mary-Jane
Ganon, Chen Li, Marion Benfell, Jagrati Singh