Taking a fresh look at urea performance in grassland Patrick - - PowerPoint PPT Presentation

Taking a fresh look at urea performance in grassland

Patrick Forrestal

• M. Harty, G.J. Lanigan, D. Wall, D. Krol, J. Murphy,
• D. Hennessy, R. Carolan, K. McGeough,

C.J. Watson, K.G. Richards

First a question for you:

• Yes
• No

What happens on your farm, have you used urea in the past year?

Urea, Why look at it now?

Cost & yield

• Urea-N costs less

than CAN-N: 26% less (CSO, 2014)

• Is there a yield

penalty?

• Internationally

urea is more available than CAN

GHG

• Ag. approx. 1/3

national emissions

• committed to

reduce by 20% by 2020

• N addition causes

N2O loss

• Smart solutions

Ammonia (NH3)

• Urea looses NH3
• Ag. accounts for c.

98.5% of national emissions

• Substantial

pressure to reduce these emissions

• n horizon

Field trials to evaluate urea performance compared with CAN

• Sites covering a range of

conditions

• Urea and stabilised urea

compared with CAN

• Applied throughout the

year, rates 0–500 kg N/ha/yr in 5 splits

• Yield response measured

by cutting

• Applied on a pre-selected

day

Urease

Nitrosomonas

et al

Nitrobacter

et al

Uptake

NH3

NO N2O N2

Uptake

NO N2O N2

N stabiliser

Annual yield under CAN, Urea, Urea+NBPT 3 sites 2 years

6000 8000 10000 12000 14000 16000 100 200 300 400 500 Grass Dry Matter Yield (kg/ha) Annual N rate (kg N/ha) CAN Urea Urea+NBPT

N concentration in grass

2.0 2.5 3.0 3.5 100 200 300 400 500 Grass N content (% N in D.M.) Annual N rate (kg N/ha) CAN Urea Urea+NBPT

Behind the average, individual cuts?

Orange: March/April applications, black summer applications

• 600
• 400
• 200

200 400 600 1 Yield difference between CAN and urea (kg/ha)

Advantage Urea Advantage CAN

Applying urea for early growth

Spring 2013 Johnstown Castle

March 19 app mean air temp (6oC) April 29 app mean air temp (10oC) Late May mean air temp (14oC)

500 1000 1500 2000 2500 3000 3500 4000 4500 20 40 60 80 100 Grass Dry Matter Yield (kg/ha) N rate (kg N/ha)

R² = 0.52 R² = 0.70 90 92 94 96 98 100 102 30 60 90 120 150 Yield from urea as a % of CAN yield N rate (kg/ha) Spring applications Summer applications

Urea compared with CAN for early growth vs summer

Combined data from current Teagasc trials and extensive work in late 1970’s early 80’s

Greenhouse gas mitigation?

Source: M. Harty et al. in prep 0.0 0.5 1.0 1.5 2.0 1 N2O emission factor (%) CAN Urea Urea+NBPT

Urea and stabilised urea: mean reduction in total N2O loss = circa 70%

Source: Forrestal, P.J., Harty, M., Carolan, R., Lanigan, G.J., Watson, C.J., Laughlin, R.J., NcNeill, G., Chambers, B., Richards, K.G. Ammonia emissions from urea, stabilised urea and calcium ammonium nitrate: insights into loss abatement in temperate grassland Soil Use and

• Management. In press.

Ammonia loss can be highly variable between applications

• Variable loss of NH3 can be an issue at all

times of the year

• Peak loss rates reached < 3 days but often

within 24 hrs

• As urea N rate increases the percentage N loss

tends to increase

• Urea stabilised with NBPT reduced NH3 loss by

78.5%

Conclusions

Cost & yield

• Urea costs less, gives comparable yield

performance to CAN but total N recovery is lower. GHG

• Urea based N offers potential to sustain or

increase national N usage with reduced N2O Ammonia

• Urea stabilised with NBPT reduced ammonia loss

by 78.5% on average

• Further understanding of ammonia loss and

development of management solutions is needed

Acknowledgements

DAFM funding through Research Stimulus Fund SUDEN & AGRI-I projects Field & lab staff, Ph.D, M.Sc, summer students, interns Partners at Agri-Food & Biosciences Institute

Questions/comments welcome