Nitrogen is essential to capture the benefit of summer rainfall for wheat in mediterranean environments of South Australia. Victor Sadras

Nitrogen is essential to capture the benefit of summer rainfall for wheat in Mediterranean environments of South Australia

Victor Sadras, Chris LawsonPeter Hooper, Glenn McDonald

South Australian Research & Development InstituteHart Field Site, The University of Adelaide

Funded by Grains R&D Corporation

Brisbane, September 2011

Climate gives rise to predictable types of ecosystems

Terry Chapin

Ryan et al. (2009) Advances in Agronomy 104:53-136

Background. Rainfall patterns as drivers of cropping systems

What is the value of summer rainfall in regions with winter-dominant rainfall?

What are the physiological mechanisms involved in the conversion of summer rainfall to yield?

What is the role of nitrogen to capture the benefit of summer rainfall?

Three features of rainfall shape cropping systems

Amount

Seasonality

Size of events

Williamson (2007)

Markham’s seasonality vector

0 20 40 60 80 100 120 140 1600

10

20

30

40

50

Plant available water at sowing (mm)

0 20 40 60 80 100 120 140 160

Fre

quen

cy (

%)

0

10

20

30

40

50(a) Emerald (b) Horsham

Rainfall seasonality drives initial soil water

median = 124 mm median = 27 mm

maximum PAW = 146 mm

Sadras & Rodriguez (2009) Australian J Agr Res 58:657-669

North-eastern environment summer rainfall

South-eastern environment winter rainfall

20 25 30 35 40

-3.6

-3.2

-2.8

-2.4

-2.0

-1.6

growing season off season

log size of event

0.0 0.5 1.0 1.5 2.0 2.5

log n

um

be

r o

f e

ve

nts

0

1

2

3

4

5

HorshamEmerald

P = 0.0004

(a)

(b)

fre

qu

en

cy o

f sm

all e

ve

nts

high

low

= -3.1

= -1.9

P = 0.08

Latitude (oS)

power laws describe size-structure of rainfall

Sadras & Rodriguez (2007) Australian J Agr Res 58:657

Size of rainfall eventsInfluence fate of water – evaporation, run-off, drainage

Sadras (2003) Australian J Agr Res 54:341-351

0

5

10

15

20

Ru

no

ff (

mm

)150 200 250 300 350 400

Seasonal rainfall (mm)

-4

0

4

8

12

2.8 3 3.2 3.4 3.6 3.8

Re

sid

ua

ls (

mm

)

(a)

(b)

P < 0.0001

Williamson (2007)

Winter half year

SE Australia vs. Syria

log size of event

0.0 0.5 1.0 1.5 2.0

log

nu

mb

er o

f eve

nts

0

1

2

3

4

5

HorshamTel Hadya

(a)

= -3.1

= -3.0

Ryan et al. (2009) Advances in Agronomy 104:53-136

Climate of SE Australia shares important features with those of the Mediterranean Basin

Australian wheat-based cropping systems match the systems that evolved over centuries in the Mediterranean basin

Australian wheat-based cropping systems are not ill-adapted European transplants

Background. Rainfall patterns as drivers of cropping systems

What is the value of summer rainfall in regions with winter-dominant rainfall?

What are the physiological mechanisms involved in the conversion of summer rainfall to yield?

What is the role of nitrogen to capture the benefit of summer rainfall?

Yield benefit from summer rainfall?

Five trials @ Roseworthy, Hart, Spalding

Seasons: 2009 and 2010

controls (background rain) vs “summer rainfall” (+50 or 100 mm)

Sadras et al (2011) European Journal of Agronomy, in press

Benefit from 20% for controls ~2 t/ha to 0 for controls ~6 t/ha

Yield of controls (t/ha)

0 2 4 6 80

2

4

6

8

y = x

y = x

0 2 4 6 8

Yie

ld o

f cro

ps w

ith

ad

dit

ion

al

su

mm

er

wate

r su

pp

ly (

t/h

a)

y = x

slope = 0.75 ± 0.070 intercept = 1.7 ± 0.30

slope = 0.81 ± 0.097 intercept = 1.4 ± 0.46

measured modelled

Background. Rainfall patterns as drivers of cropping systems

What is the value of summer rainfall in regions with winter-dominant rainfall?

What are the physiological mechanisms involved in the conversion of summer rainfall to yield?

What is the role of nitrogen to capture the benefit of summer rainfall?

0 50 100 150 200

Sh

oo

t d

ry m

atte

r (k

g/h

a)

0

2000

4000

6000

8000control+50 mm+100 mm

GS 32 GS 65 GS 95

***

*****

Days after sowing

PA

R i

nte

rce

pti

on

(%

)

0

20

40

60

80

100

Days after sowing0 50 100 150 200

Cu

mu

lati

ve

evap

otr

an

sp

irati

on

(m

m)

0

100

200

300

5 d after irrigation

0 10 20 30 40

-120

-90

-60

-30

0******************

******

control+50 mm+100 mm

So

il d

epth

(cm

)

Soil water content (mm)

Soil water content (mm)

So

il d

epth

(cm

)

sowing

0 10 20 30 40

-120

-90

-60

-30

0

*

*********

control

+100mm

stem elongation

0 10 20 30 40

So

il d

ep

th

(c

m)

-120

-90

-60

-30

0

******

Soil water content (mm)

So

il d

ep

th

(c

m)

control

flowering

0 10 20 30 40

-120

-90

-60

-30

0

***S

oil

dep

th (

cm)

Soil water content (mm)

maturity

0 10 20 30 40

-120

-90

-60

-30

0

*

**

Soil water content (mm)

So

il d

epth

(cm

)

Residual water at maturity in N-deficient crops Roseworthy, 2010

0 5 10 15

-100

-80

-60

-40

-20

0S

oil

dep

th (

cm)

Soil water content (mm)

low N

high N

maturity

r = 0.94P <0.0001

Grain number (per m2)

0 5000 10000 15000 20000

Yie

ld (

kg/h

a)

0

2000

4000

6000

8000

bare ground, Exps 1, 2stubble, Exps 1, 2high H, Exps 3-5low N, Exps 3-5

r = 0.65P <0.002

Crop growth rate (kg ha-1 d-1)

0 50 100 150 200

Gra

in n

um

ber

(m-2)

0

5000

10000

15000

20000

bare ground, Exps 1, 2stubble, Exps 1, 2high H, Exps 3-5low N, Exps 3-5

P < 0.02

Nitrogen rate

low high

Gra

ins m

-2 per u

nit g

row

th ra

te

(ha d

kg

-1)

0

50

100

(b)(c)

Grain number accounted for 88% of the variation in yield

r = 0.94P <0.0001

Grain number (per m2)

0 5000 10000 15000 20000

Yie

ld (

kg

/ha

)

0

2000

4000

6000

8000

bare ground, Exps 1, 2stubble, Exps 1, 2high H, Exps 3-5low N, Exps 3-5

r = 0.65P <0.002

Crop growth rate (kg/ha/d)

0 50 100 150 200

Gra

in n

um

be

r (p

er

m2)

0

5000

10000

15000

20000

bare ground, Exps 1, 2stubble, Exps 1, 2high H, Exps 3-5low N, Exps 3-5

P < 0.02

Nitrogen rate

low high

Gra

ins m -2

pe

r un

it gro

wth

rate

(ha

d k

g -1)

0

50

100

(b)(c)

Grain number = f (CGR between stem elongation and anthesis)

Low N

Variable 0 mm 0 mm +100mm +100mm PW PN PX Low N High N Low N High N Shoot biomass (t/ha) 12.3 11.8 12.2 15.6 ** ** ** Yield (t/ha) 5.8 5.6 5.7 7.2 ** ** ** Grain number (103 x m-2) 13.0 13.8 12.8 17.1 * ** * Harvest Index 0.42 0.42 0.42 0.42 - - - Grain size (mg) 42.7 39.3 42.5 40.2 - - - RUE (g/MJ) 1.64 1.57 1.50 1.89 - * ** Biomass/ET (kg/ha. mm) 34.9 33.0 32.2 40.0 - - ** Yield/ ET (kg/ha. mm) 15.9 15.3 14.5 18.0 - * **

Variable 0 mm 0 mm +100mm +100mm PW PN PX Low N High N Low N High N Shoot biomass (t/ha) 12.3 11.8 12.2 15.6 ** ** ** Yield (t/ha) 5.8 5.6 5.7 7.2 ** ** ** Grain number (103 x m-2) 13.0 13.8 12.8 17.1 * ** * Harvest Index 0.42 0.42 0.42 0.42 - - - Grain size (mg) 42.7 39.3 42.5 40.2 - - - RUE (g/MJ) 1.64 1.57 1.50 1.89 - * ** Biomass/ET (kg/ha. mm) 34.9 33.0 32.2 40.0 - - ** Yield/ ET (kg/ha. mm) 15.9 15.3 14.5 18.0 - * **

Variable 0 mm 0 mm +100mm +100mm PW PN PX Low N High N Low N High N Shoot biomass (t/ha) 12.3 11.8 12.2 15.6 ** ** ** Yield (t/ha) 5.8 5.6 5.7 7.2 ** ** ** Grain number (103 x m-2) 13.0 13.8 12.8 17.1 * ** * Harvest Index 0.42 0.42 0.42 0.42 - - - Grain size (mg) 42.7 39.3 42.5 40.2 - - - RUE (g/MJ) 1.64 1.57 1.50 1.89 - * ** Biomass/ET (kg/ha. mm) 34.9 33.0 32.2 40.0 - - ** Yield/ ET (kg/ha. mm) 15.9 15.3 14.5 18.0 - * **

Variable 0 mm 0 mm +100mm +100mm PW PN PX Low N High N Low N High N Shoot biomass (t/ha) 12.3 11.8 12.2 15.6 ** ** ** Yield (t/ha) 5.8 5.6 5.7 7.2 ** ** ** Grain number (103 x m-2) 13.0 13.8 12.8 17.1 * ** * Harvest Index 0.42 0.42 0.42 0.42 - - - Grain size (mg) 42.7 39.3 42.5 40.2 - - - RUE (g/MJ) 1.64 1.57 1.50 1.89 - * ** Biomass/ET (kg/ha. mm) 34.9 33.0 32.2 40.0 - - ** Yield/ ET (kg/ha. mm) 15.9 15.3 14.5 18.0 - * **

Variable 0 mm 0 mm +100mm +100mm PW PN PX Low N High N Low N High N Shoot biomass (t/ha) 12.3 11.8 12.2 15.6 ** ** ** Yield (t/ha) 5.8 5.6 5.7 7.2 ** ** ** Grain number (103 x m-2) 13.0 13.8 12.8 17.1 * ** * Harvest Index 0.42 0.42 0.42 0.42 - - - Grain size (mg) 42.7 39.3 42.5 40.2 - - - RUE (g/MJ) 1.64 1.57 1.50 1.89 - * ** Biomass/ET (kg/ha. mm) 34.9 33.0 32.2 40.0 - - ** Yield/ ET (kg/ha. mm) 15.9 15.3 14.5 18.0 - * **

N-driven trade-off between WUE and NUE

0 100 200 300

Wat

er u

se e

ffic

ien

cy(k

g/h

a m

m)

0

5

10

15

20

Nitro

gen

utilisatio

n efficien

cy(kg

grain

/kgN

)

0

10

20

30

40

Nitrogen rate (kg N/ha)

WUE

NUE

Sadras & Rodriguez (2010) Field Crops Research 118, 297–305.

1. Summer rainfall can contribute up to 20% gains in yield of wheat in South Australia

2. Yield gains are related to early growth and grain number

3. Grain number is a function of growth rate in the window between stem elongation and anthesis

4. Supply of both nitrogen and water in this critical window is essential

5. Has the balance between growth before and after anthesis been overemphasised?

Summary

The trade-off is universal – applies to maize in USA corn-belt

0 50 100 15015

20

25

30

40

50

60

70

80WUE

NUE

Nitro

gen

utilisatio

n efficien

cy(kg

grain

per kg

N)W

ater

use

eff

icie

ncy

(kg

/ha/

mm

)

Nitrogen rate (kg N/ha)

The trade-off is universal – applies to rice in Philippines

0 150

Wat

er u

se e

ffic

ien

cy

(kg

/ha/

mm

)

0

2

4

6

50

55

60

65

WUE

NUE

Nitro

ge

n u

tilisation

efficiency

(kg g

rain

/kg N

)

Nitrogen rate (kg N/ha)