How will the impact of elevated carbon dioxide on grain production

vary with different soils?R Armstrong, R Lam, J Jin, N Mathers, D Chen, R Norton,

J Jin, C Tang, P Sale, M Mollah, R Perris, and M Munn

Background

Increased atmospheric CO2 generally:- Increased NPP resulting from greater photosynthetic

efficiency & improved transpiration efficiency.

- Increased A/G biomass requires greater nitrogen supply

- These effects are not always translated to grain yield

- Development of ‘progressive nitrogen limitation’ over time

FACE are confined to specific soils &climates

To understand atmospheric * aboveground physiological processes, you must also know

what is occurring belowground!

1. Impact of eCO2 on soil:plant mechanisms regulating root access nutrients and water better understood.

2. Influence of soil type on nutrient supply to grain crops under eCO2 assessed.

3. Use data to improve predictions (simulations) of the impact of eCO2 on grain production systems

Objectives

Figure 1: Soils FACE ArrayLegend

ambient

elevatedtrack

elevated

99 metres

5 (E) 6 (F) 7 (G) 8 (H) ambient

Hamilton

Rd27 m

1 (A) 2 (B) 3 ( C) 4 (D)

4.5 m

99 m30 m

80 m

channel

FACE - Grains Array

CO2 tank

N

Design

• Focus on belowground processes- Root function, Nutrient cycling (esp. N and P), N2 fixation Above and belowground 15N/13C distribution; soil C dynamics

and root disease

2 CO2 * 2 phases * 3 soil types * 4 reps

1. eCO2 (550 ppm) vs ambient

2. Phases: Yipti wheat and Fieldpeas (Kaspar line) (+ spare chickpeas)

3. Soils: Calcarosol (Mallee) ; Vertosol (Wimmera) ; Chromosol (HRZ)

- Non irrigated ; first phase sown in 2009

Results (2009) – first crop

• No effect of eCO2 on dry matter, shoot %N, shoot N uptake, %Ndfa, N fixed or grain yield or in-situ

soil N mineralisation

• Large effect of soil type on all variables

• No interaction between soil type * eCO2

Results (2010) : 2nd crop (Decile 10 GSR)Influence of eCO2 and soil type on the growth, N uptake and N fixation of

field peas in SoilFACE (Oct 2010)

ANOVACO2 0.06 n.s. n.s. n.s.Soil type <0.001 <0.001 <0.001 <0.001CO2 x Soil 0.039 0.06 n.s. 0.038

CO2 treatment Dry matter (g/core)

N uptake (mg/core)

Ndfa (%)

N fixed (mg/core)

(i) Walpeup

Ambient 32.6 714 49.9 379 eCO2 28.1 581 58.9 334

(ii) Horsham

Ambient 60.1 1329 55.0 451 eCO2 96.0 1954 64.6 995

(iii) Hamilton

Ambient 47.1 1018 9.1 81 eCO2 57.7 960 10.7 63

Soil Mineral N at Sowing in 2010

0

20

40

60

80

100

0 2 4 6 8 10

Soil Mineral N (mg/kg)

Soi

l dep

th (c

m)

Ham amb

Ham eCO2

Hors amb

Hors eCO2

Walp amb

Walp eCO2

Hamilton >>> Horsham > Walpeup

Some differences in response of fieldpeas & wheat to eCO2 (grain maturity: Dec 2010)

ANOVA

CO2 0.083 0.074 n.s. 0.034

Soil type <0.001 <0.001 <0.001 <0.001

CO2 x Soil n.s. n.s. n.s. n.s.

CO2 treatment Dry matter (g/core)

Grain yield (g/core)

wheat fieldpeas wheat fieldpeas

(i) Walpeup Ambient 15.2 46.2 6.1 24.5

eCO2 22.0 50.0 8.1 28.8 (ii) Horsham

Ambient 63.0 74.2 25.3 39.1 eCO2 65.2 91.0 24.7 48.8

(iii) Hamilton Ambient 56.6 51.0 18.9 23.4

eCO2 67.3 66.2 22.7 32.7

Effect of eCO2 on P response of pulses

Aims: Examine effect of eCO2 on

- Internal and external P requirements

- Root growth & morphology

- Changes in rhizosphere P fractions

Design:Amb/eCO2 x 5 soil P concs x 4 reps

- P deficient vertosol

- Chickpeas and Fieldpeas

P applied (mg/ kg soil) P applied (mg/ kg soil)

Strong A/G dm interaction between eCO2 & soil P in both pulses

P applied (mg/kg soil)

Shoot P content in field pea

Strong A/G interaction between eCO2 & soil P on nutrient uptake in both pulses

0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000

Root length (cm)

Dep

th (c

m)

Amb P0

Amb P16

eCO2 P0

eCO2 P16

Chickpea

Interaction between eCO2 and soil P supply on changes in belowground growth eg. root length

0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000

Root length (cm)

Dep

th (

cm)

Amb P0

Amb P16

eCO2 P0

eCO2 P16

Fieldpea

P applied (mg/kg soil)

The effect of eCO2 on nutrient dynamics eg. distribution of plant P cannot always be predicted

from A/G data

Conclusions• Strong effect of soil type

• N fixation dominated by dry matter response to eCO2 and

background soil mineral N

• Response to eCO2 varies with soil P (as well as N) & species

• Changes in belowground nutrient dynamics cannot be always be predicted by aboveground content

• Impossible to predict long term effect of eCO2 on B/G processes at this stage (system is not at equilibrium) eg. PNL?

Thankyou

Mass spectrometer (15N, 13C stable isotopes) for solids, liquids & gases

15N Leaf feeding technique to estimate below ground N distribution

Results (2009)

CCOO22 ttrreeaattmmeenntt

DDrryy mmaatttteerr ((gg//ccoorree))

SShhoooott NN ((%%))

NN uuppttaakkee ((gg//ccoorree))

NNddffaa ((%%))

NN ffiixxeedd ((gg//ccoorree))

(i) Walpeup ambient 48.7 1.80 0.85 36.8 0.31 eCO2 47.6 1.82 0.83 17.7 0.16

(ii) Horsham ambient 86.0 1.94 1.69 34.2 0.55 eCO2 96.4 1.74 1.68 38.7 0.66

(iii) Hamilton ambient 69.6 1.58 1.10 20.1 0.27 eCO2 72.5 1.39 1.04 24.5 0.28

ANOVACO2 n.s. n.s. n.s. n.s. n.s.Soil type ** * * n.s. **CO2 x Soil n.s. n.s. n.s. n.s. n.s.

Table 1: Influence of elevated carbon dioxide (550 ppm) and soil type on the growth, N uptake and N fixation of field peas in SoilFACE (2009)

Thankyou

pH of Subsoil

Distribution of soils (by pH) throughout Australian grain producing regions