Nitrogen Use it or lose itEmission story

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De Ferrier BCG, Ash Wallace DPI Vic

1. As a rule of thumb how much nitrogen does a wheat crop need to produce 1 t/ha of grain?

1 2 3 4 5

11%

40%

7%

31%

11%

1. 10 kg N/ha (22 kg urea/ha)

2. 20 kg N/ha (43 kg urea/ha)

3. 30 kg N/ha (65 kg urea/ha)

4. 40 kg N/ha (87 kg urea/ha)

5. Unsure

2. When determining how much nitrogen is needed for a wheat crop what do you do?

1 2 3 4 5 6

21% 21%

61%

31%

24%21%

1. I use a rule of thumb such as 40 kg N/ha per tonne of wheat

2. I apply what my agronomist tells me

3. I use a decision support tool such as Yield Prophet or an excel spreadsheet

4. I use soil or tissue tests

5. I use gut feel

6. I use a range of advice and tools

3. How do you rate your understanding of nitrogen losses?

1 2 3 4

3% 6%

62%

29%

1. Excellent

2. Good

3. Low

4. None at all

How much do you know about nitrous oxide emissions and their effect on productivity and

greenhouse gases?

1 2 3 4

57%

7%13%

23%

1. Nothing

2. A little

3. A bit

4. Quite a lot

How much nitrous oxide is lost from a cropping paddock in low rainfall areas annually?

1 2 3 4 5

6%

25%

10%10%

49%1. 0.1-0.5 kg N/ha

2. 1-2 kg N/ha

3. 10-20 kg N/ha

4. 30-40 kg N/ha

5. 50-100 kg N/ha

The global warming potential (GWP) of a gas measures the amount of heat it can trap in the atmosphere. Carbon dioxide has a GWP of 1.

1 2 3 4 5

32%

26%

12%

5%

24%

1. 10:1

2. 50:1

3. 298:1

4. 310:1

5. 450:1

What is the GWP of nitrous oxide compared to carbon dioxide?

What are we measuring?

•The main levers that control emissions:

What drives N2O losses?

Soil water Soil nitrogen

Crop management can alter these levers

Minimising N loss is good for productivity

= win win

Soil carbon

Soil temperature

Why are we measuring it?

• Limited research into the grains industry’s N2O emission contribution in low rainfall environments

• Govt policy is forever changing and uncertain (agricultural, environmental, political implications)

• Better communication needed to a wider audience• Since the 2002-2009 drought more efficient and prescribed

approach to nitrogen use.

• Nitrogen better match between crop demand and seasonal conditions.

• Need to inform accounting protocols – particularly legumes

GSR: 212mm Soil moisture: 42mm Sowing date: 19 JuneVariety: DerrimutPotential yield: 2.8t/ha

To apply zero, medium and high urea rates and measure

•N2O fluxes from soil in a wheat crop

•the effect on wheat yield and quality

Site: Rupanyup

Nitrous oxide (N2O) losses from low rainfall environments

How did we do it?

Urea applied N appliedkg/ha kg/ha

Zero 0 0Medium 180 83 2 t/ha

High 450 207 5 t/ha

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What did we expect to find?

0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14

N lo

ss

pe

r d

ay Fertiliser added

Zero fertiliser

What did we find?

Figure 1. N2O flux obtained (4, 6, 7, 14 September) before and after urea application at Rupanyup.

Low N2O lossesPeak levels were 4.5g N/ha/day

6 Sep = 0.3mm, 7 Sep = 8.13mm, 8 Sep =0.5mm, 13 Sep = 0.5mm

1 day prior

1 day after

1 week later

4th SepUrea0 kg/ha4080

Dimboola grain prices @ December 3. Urea $620/t

Treatment Nitrogen rate Urea rate Yield Protein Quality Grain price Income Urea cost Income less urea cost NUE(kg/ha) (kg/ha) (t/ha) (%) ($/ha) ($/ha) ($) ($/ha) %

Zero 0 0 2.3 7.6c ASW 251 577 0 570Medium 83 180 2.8 11.0b APW1 274 767 112 652 34High 207 450 2.8 14.2a H1 299 837 279 510 14Sig. diff. NS P<0.001 NSLSD (P=0.05) 0.72CV% 3.8

What did we find?

Urease inhibitors

Can we do anything about it?

Nitrification inhibitors

Can we do anything about it?

• Improve nitrogen use efficiency

• Timing, N in front of rain

• Type of product

• Tools

• Soil test

• Rotations

Can we do anything about it?

Take Home Messages

• Measured N2O fluxes are low in the Wimmera Mallee low compared to accounting methods.

• Ammonia likely to be more important from a productivity perspective.

• Products and tools are available to reduce losses. New products being investigated.

• Use it don’t lose it!!

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