How does urea and protected urea

compare to CAN for spring barley

production

L.Roche1,2, P.J. Forrestal1, R. Hackett, G.Lanigan1,K.G.

Richards1, L.J Shaw2, D.P. Wall1

1Teagasc, Crops Environment and Land Use Programme,

Johnstown Castle, Wexford, Ireland 2University of Reading

3 Teagasc, Crops Research Centre, Oak Park, Co.Carlow

Background

• Greenhouse gas emission (GHG) reduction targets

• Agriculture is responsible for 33% of GHGs

• N fertiliser contributes to GHGs

• Ammonia emission reduction targets

• Agriculture is responsible for 98% of ammonia emissions

• Urea contributes to ammonia emissions

• Water Quality

• Losses of N fertiliser is damaging to water quality

• Requirements under Water Framework and Nitrates directives

• Food Wise 2025

• Increase the value of primary production by 65%

Background – N Fertiliser

CAN

• 27% N

• 13.5% of N in CAN is nitrate and can be easily lost

• N losses as nitrous oxide (potent greenhouse gas) and nitrate leaching

• Using urea could reduce these losses

Urea

• 46% N

• Urea must go through two conversions before N converts to nitrate

• N loss as ammonia volatilisation (indirect greenhouse gas)

• Use of protected urea

Urea Ammonium (NH4

+) Nitrate

(NO3-)

CAN CAN NBPT

Protected Urea

NH3 N2O

Urea Hydrolysis Nitrification

Denitrification Volatilisation

Leaching SOIL

Plant N uptake

D.P Wall 2015

Deposition

Protected Urea

• Protected urea fertilisers are now available on the market in Ireland

• In this study – urea + N-(n-butyl) thiophosphoric triamide (NBPT) is used

• The protected urea product used in these trials contained NBPT at 660 ppm.

Experimental Design

• Field site

• Marshalstown, Co. Wexford – free draining loam

• >20 years spring barley production

• Randomised block design with 5 replicates of each treatment

• N fertiliser treatments used (N rate 150 kg N/ha)

• Unfertilised control

• CAN

• Urea

• Protected urea (Urea + NBPT)

• Fertiliser N applied in 2 splits

• 1st split – 30 kg N/ha applied at sowing

• 2nd split – 120 kg N/ha applied at mid-tillering

• Nitrous oxide emissions measured after N application

• Crop Harvested in late August each year

Long-term arable

Free-draining loam

Results

Nitrous Oxide emissions

0.84

0.71

0.6

0.31

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

CAN Urea Protected Urea Control

Nit

rou

s o

xid

e (k

g N

2O

-N/h

a/ye

ar)

Ammonia Emissions

-5

0

5

10

15

20

25

30

0 5 10 15 20 25

Cu

mu

lati

ve k

g N

/ha

Days after fertiliser application

Urea

Ammonia Emissions

-5

0

5

10

15

20

25

30

0 5 10 15 20 25

Cu

mu

lati

ve k

g N

/ha

Days after fertiliser application

Urea

Protected Urea

Nitrate Leaching

0

10

20

30

40

50

60

70

CAN Urea Control

Cu

mu

lati

ve N

itra

te le

ach

ing

(kg/

ha/

year

)

Grain Yield over 3 years (2013, 2014, 2015)

0

1

2

3

4

5

6

7

8

9

10

2013 2014 2015

Spri

ng

bar

ley

grai

n y

ield

(t/

ha)

CAN

Urea

Protected Urea

Control

Average Grain Yield over 3 years

8.3 8.4 8.6

3.1

0

1

2

3

4

5

6

7

8

9

CAN Urea Protected Urea Control

Spri

ng

bar

ley

grai

n Y

ield

(t/

ha)

N uptake over 3 years (2013, 2014, 2015)

0

20

40

60

80

100

120

140

160

180

2013 2014 2015

Cro

p N

Up

take

(kg

/ha)

CAN

Urea

Protected Urea

Control

Average N uptake over 3 years

135.7 130.7

149.0

52.6

0

20

40

60

80

100

120

140

160

CAN Urea Protected Urea Control

Cro

p N

Up

take

(kg

/ha)

Average Protein % over 3 years

9.2 9.3 9.6

9.1

0

1

2

3

4

5

6

7

8

9

10

11

12

CAN Urea Protected Urea Control

Pro

tein

(%

)

Relative Star rating of CAN, urea and protected urea

Conclusions

• Greenhouse gas emissions

• Overall N2O was low from all fertilisers

• Protected urea had lower emissions than CAN

• Ammonia Emissions

• Ammonia loss from urea approximately 25kg

• Protected urea reduced ammonia loss to < 5 kg

• Grain Yield

• Grain Yield similar for all fertilisers

• On average 0.3 t/ha more yield with protected urea

• N Uptake and Protein

• N Uptake and protein highest with protected urea

Overall, using protected urea is a win-win for farmers and

environment

Thank you for your attention

Acknowledgments

Walsh Fellowship Funding

DAFM for funding through research stimulus fund

All field and lab staff at Teagasc Oakpark and Johnstown Castle

James Masterson for access to the field site