How will the impact of elevated carbon dioxide on grain production vary with different soils? - Roger Armstrong

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How will the impact of elevated carbon dioxide on grain production vary with different soils? - Roger Armstrong

  1. 1. 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
  2. 2. Background <ul><li>Increased atmospheric CO 2 generally: </li></ul><ul><li>Increased NPP resulting from greater photosynthetic </li></ul><ul><li>efficiency & improved transpiration efficiency. </li></ul><ul><li>- Increased A/G biomass requires greater nitrogen supply </li></ul><ul><li>- These effects are not always translated to grain yield </li></ul><ul><li>- Development of ‘progressive nitrogen limitation’ over time </li></ul>
  3. 3. FACE are confined to specific soils &climates
  4. 4. To understand atmospheric * aboveground physiological processes, you must also know what is occurring belowground!
  5. 5. <ul><li>Impact of eCO2 on soil:plant mechanisms regulating root access nutrients and water better understood. </li></ul><ul><li>Influence of soil type on nutrient supply to grain crops under eCO2 assessed. </li></ul><ul><li>Use data to improve predictions (simulations) of the impact of eCO2 on grain production systems </li></ul>Objectives
  6. 7. Design <ul><li>2 CO 2 * 2 phases * 3 soil types * 4 reps </li></ul><ul><li>Focus on belowground processes </li></ul><ul><li>- Root function, Nutrient cycling (esp. N and P), N2 fixation Above and belowground 15 N/ 13 C distribution; soil C dynamics and root disease </li></ul><ul><li>eCO2 (550 ppm) vs ambient </li></ul><ul><li>Phases: Yipti wheat and Fieldpeas (Kaspar line) (+ spare chickpeas) </li></ul><ul><li>Soils: Calcarosol (Mallee) ; Vertosol (Wimmera) ; Chromosol (HRZ) </li></ul>- Non irrigated ; first phase sown in 2009
  7. 8. Results (2009) – first crop <ul><li>No effect of eCO 2 on dry matter, shoot %N, shoot N uptake, %Ndfa, N fixed or grain yield or in-situ soil N mineralisation </li></ul><ul><li>Large effect of soil type on all variables </li></ul><ul><li>No interaction between soil type * eCO 2 </li></ul>
  8. 9. Results (2010) : 2 nd 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) ANOVA CO 2 0.06 n.s. n.s. n.s. Soil type <0.001 <0.001 <0.001 <0.001 CO 2 x Soil 0.039 0.06 n.s. 0.038
  9. 10. Soil Mineral N at Sowing in 2010 Hamilton >>> Horsham > Walpeup
  10. 11. 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.
  11. 12. Effect of eCO 2 on P response of pulses Aims: Examine effect of eCO 2 on - Internal and external P requirements - Root growth & morphology - Changes in rhizosphere P fractions <ul><li>Design: </li></ul><ul><li>Amb/eCO 2 x 5 soil P concs x 4 reps </li></ul><ul><li>P deficient vertosol </li></ul><ul><li>Chickpeas and Fieldpeas </li></ul>
  12. 13. P applied (mg/ kg soil) P applied (mg/ kg soil) Strong A/G dm interaction between eCO2 & soil P in both pulses
  13. 14. 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
  14. 15. Interaction between eCO2 and soil P supply on changes in belowground growth eg. root length Fieldpea Chickpea
  15. 16. The effect of eCO2 on nutrient dynamics eg. distribution of plant P cannot always be predicted from A/G data P applied (mg/kg soil)
  16. 17. Conclusions <ul><li>Strong effect of soil type </li></ul><ul><li>N fixation dominated by dry matter response to eCO 2 and background soil mineral N </li></ul><ul><li>Response to eCO2 varies with soil P (as well as N) & species </li></ul><ul><li>Changes in belowground nutrient dynamics cannot be always be predicted by aboveground content </li></ul><ul><li>Impossible to predict long term effect of eCO2 on B/G processes at this stage (system is not at equilibrium) eg. PNL? </li></ul>
  17. 18. Thankyou
  18. 19. Mass spectrometer ( 15 N, 13 C stable isotopes) for solids, liquids & gases 15 N Leaf feeding technique to estimate below ground N distribution
  19. 20. Results (2009) 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) ANOVA CO 2 n.s. n.s. n.s. n.s. n.s. Soil type ** * * n.s. ** CO 2 x Soil n.s. n.s. n.s. n.s. n.s.
  20. 21. Thankyou
  21. 22. Distribution of soils (by pH) throughout Australian grain producing regions

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