A field study on the impact of the nitrification inhibitor DMPP on N2O emissions from a pasture in south western VictoriaHelen Suter, Humaira Sultana and Deli Chen(The University of Melbourne)

Rohan Davies and Matthew Mahoney(Incitec Pivot)

Nitrification and inhibitors

NH4+ NO3

-nitrification

(eg. Nitrosomonas)

denitrification

N2O

N2

Nitrification inhibitor eg. Dimethylpyrazole phosphate (DMPP)

Urea

hydrolysis

N2O

Experimental methodology

Treatments • Control• Urea• Urea with Entec® = Urea + DMPP ( Dimethyl pyrazole phosphate)

5 replicates/treatment

• 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

• Start date: 12 April 2010

• End date: 23 December 2010

• Fertilisation events: 7

• Gas collection: manual chambers (23 x 20 cm)

Source: Google maps

Experimental methodology

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

Results: Daily N2O emissions (April-Oct)

0

5

10

15

20

25

30

35

40

45

Calc

ulat

ed d

aily

N2O

(g/h

a)

control

urea

DMPP

fertiliser application at 40 kg N/ha

site waterlogged, no sampling

Results: Daily N2O emissions and rainfall (April-Oct)

(Total rainfall 522 mm)0

5

10

15

20

25

30

35

40

Rai

nfal

l (m

m)

0

5

10

15

20

25

30

35

Calc

ulat

ed d

aily

N 2O

(g/h

a)

control

urea

DMPP

fertiliser application at 40 kg N/ha

site waterlogged, no sampling

Results: Daily N2O emissions and daily mean maximum temperature (April-Oct)

0

5

10

15

20

25

30

35

Calc

ulat

ed d

aily

N 2O

(g/h

a)

control

urea

DMPP

fertiliser application at 40 kg N/ha

site waterlogged, no sampling

0

5

10

15

20

25

30

Tem

pera

ture

(o C)

Results: Cumulative Net-N2O emissions

0

50

100

150

200

250

300

350

400

450

Calc

ulat

ed c

umul

ative

Net

-N2O

(g/

ha) Urea

DMPP

73% reduction

fertiliser application at 40 kg N/ha

Results : soil nitrate levels

0

2

4

6

8

10

12

14

16

18

Nitr

ate

-N (k

g/ha

) Control

DMPP

Urea

Results : soil nitrate levels and potential for leaching loss

0

5

10

15

20

25

30

35

40

Rain

fall

(mm

)0

2

4

6

8

10

12

14

16

18

Nitr

ate

-N (k

g/ha

)

Control

DMPP

Urea

Results : soil nitrate levels and potential for leaching loss

0

5

10

15

20

25

30

35

40

Rain

fall

(mm

)0

2

4

6

8

10

12

14

16

18

Nitr

ate

-N (k

g/ha

)

Control

DMPP

Urea

Potential for leaching losses reduced with DMPP

Results : Dry Matter (DM) production (kg/ha)

Treatment 10-May 7-Jun* 19-Jul 3-Sep 27-Sep 21-OctCumulative(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

DMPP18 89 14 12 -11 1 6

* 7 June sampling comes 2 months after fertilisation on 12 April

(Value is average of 5 reps ± standard error)

Results : Dry Matter (DM) production (kg/ha)

Treatment 10-May 7-Jun* 19-Jul 3-Sep 27-Sep 21-OctCumulative (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

DMPP18 89 14 12 -11 1 6

* 7 June sampling comes 2 months after fertilisation on 12 April

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

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