Abstract
Abstract The response of wheat crops to elevated CO 2 ( eCO 2 ) was measured and modelled with the Australian Grains Free‐Air CO 2 Enrichment experiment, located at Horsham, Australia. Treatments included CO 2 by water, N and temperature. The location represents a semi‐arid environment with a seasonal VPD of around 0.5 kP a. Over 3 years, the observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha −1 and 1600 to 3900 kg ha −1 , respectively, over various sowing times and irrigation regimes. The mean observed response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 ) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively. Seasonal water use was decreased from 320 to 301 mm ( P = 0.10) by eCO 2 , increasing water use efficiency for biomass and yield, 36% and 31%, respectively. The performance of six models (APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST , OLEARY ‐ CONNOR and SALUS ) in simulating crop responses to eCO 2 was similar and within or close to the experimental error for accumulated biomass, yield and water use response, despite some variations in early growth and LAI . The primary mechanism of biomass accumulation via radiation use efficiency ( RUE ) or transpiration efficiency ( TE ) was not critical to define the overall response to eCO 2 . However, under irrigation, the effect of late sowing on response to eCO 2 to biomass accumulation at DC 65 was substantial in the observed data (~40%), but the simulated response was smaller, ranging from 17% to 28%. Simulated response from all six models under no water or nitrogen stress showed similar response to eCO 2 under irrigation, but the differences compared to the dryland treatment were small. Further experimental work on the interactive effects of eCO 2 , water and temperature is required to resolve these model discrepancies.
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Claims 16
Claim · model-written summary
Observed wheat biomass at anthesis ranged from 4200 to 10 200 kg ha −1 across sowing and irrigation regimes.
- Taxon
- wheat
Triticum aestivumt0 - Outcome
- biomass at anthesise0
- Value
- 4200 to 10 200 kg ha −1e0
- Qualifier
- various sowing times and irrigation regimese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha −1 and 1600 to 3900 kg ha −1 , respectively, over various sowing times and irrigation regimes”
t0“wheat”
Claim · model-written summary
Observed wheat grain yield ranged from 1600 to 3900 kg ha −1 across sowing and irrigation regimes.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- grain yielde0
- Value
- 1600 to 3900 kg ha −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha −1 and 1600 to 3900 kg ha −1 , respectively, over various sowing times and irrigation regimes”
t0“wheat”
Claim · model-written summary
Elevated CO2 increased wheat biomass at stem elongation by 21%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- eCO 2e0
- Outcome
- biomass at stem elongatione0
- Direction
- increaseinferrede0
- Value
- 21%e0
- Comparator
- 365e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 ) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively”
t0“wheat”
Claim · model-written summary
Elevated CO2 increased wheat biomass at anthesis by 23%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- eCO 2e0
- Outcome
- biomass at anthesise1
- Direction
- increaseinferrede0
- Value
- 23%e0
- Comparator
- 365e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 ) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively”
e1“observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha −1 and 1600 to 3900 kg ha −1 , respectively, over various sowing times and irrigation regimes”
t0“wheat”
Claim · model-written summary
Elevated CO2 increased wheat LAI at anthesis by 21%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- eCO 2e0
- Outcome
- LAI at anthesise0
- Direction
- increaseinferrede0
- Value
- 21%e0
- Comparator
- 365e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 ) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively”
t0“wheat”
Claim · model-written summary
Elevated CO2 increased wheat grain yield by 26%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- eCO 2e0
- Outcome
- grain yielde0
- Direction
- increaseinferrede0
- Value
- 26%e0
- Comparator
- 365e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 ) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively”
t0“wheat”
Claim · model-written summary
Elevated CO2 decreased seasonal wheat water use from 320 to 301 mm.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- eCO 2e0
- Outcome
- Seasonal water usee0
- Direction
- decreasede0
- Value
- 320 to 301 mme0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seasonal water use was decreased from 320 to 301 mm ( P = 0.10) by eCO 2”
t0“wheat”
Claim · model-written summary
Elevated CO2 increased wheat biomass water use efficiency by 36%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- eCO 2e1
- Outcome
- water use efficiency for biomasse0
- Direction
- increasinge0
- Value
- 36%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing water use efficiency for biomass and yield, 36% and 31%, respectively”
e1“response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 )”
t0“wheat”
Claim · model-written summary
Elevated CO2 increased wheat yield water use efficiency by 31%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing water use efficiency for biomass and yield, 36% and 31%, respectively”
e1“response to daytime eCO 2 (from 365 to 550 μmol mol −1 CO 2 )”
t0“wheat”
Claim · model-written summary
Six models simulated wheat accumulated biomass, yield, and water use responses to elevated CO2 within or near experimental error.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- accumulated biomass, yield and water use responsee0
- Comparator
- experimental errore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The performance of six models (APSIM‐Wheat, APSIM‐Nwheat, CAT‐Wheat, CROPSYST , OLEARY ‐ CONNOR and SALUS ) in simulating crop responses to eCO 2 was similar and within or close to the experimental error for accumulated biomass, yield and water use response”
t0“wheat”
Claim · model-written summary
The six wheat models varied in early growth and LAI simulations.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- early growth and LAIe0
Not reportedComparatorValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite some variations in early growth and LAI”
t0“wheat”
Claim · model-written summary
The choice of radiation use efficiency or transpiration efficiency as biomass mechanism was not critical for defining wheat elevated-CO2 response.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- overall response to eCO 2e0
- Qualifier
- radiation use efficiency ( RUE ) or transpiration efficiency ( TE )e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The primary mechanism of biomass accumulation via radiation use efficiency ( RUE ) or transpiration efficiency ( TE ) was not critical to define the overall response to eCO 2”
t0“wheat”
Claim · model-written summary
Under irrigation, late sowing produced an observed wheat biomass response to elevated CO2 of about 40% at DC 65.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- late sowinge0
- Outcome
- biomass accumulation at DC 65e0
- Direction
- substantiale0
- Value
- ~40%e0
- Qualifier
- under irrigatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under irrigation, the effect of late sowing on response to eCO 2 to biomass accumulation at DC 65 was substantial in the observed data (~40%)”
t0“wheat”
Claim · model-written summary
Models predicted a smaller late-sowing wheat biomass response to elevated CO2 of 17% to 28%.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- simulated responsee0
- Direction
- smallere0
- Value
- 17% to 28%e0
- Comparator
- observed datae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the simulated response was smaller, ranging from 17% to 28%”
e1“the observed data (~40%)”
t0“wheat”
Claim · model-written summary
All six wheat models gave similar elevated-CO2 response without water or nitrogen stress under irrigation, with small differences from dryland treatment.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- response to eCO 2e0
- Comparator
- dryland treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Simulated response from all six models under no water or nitrogen stress showed similar response to eCO 2 under irrigation, but the differences compared to the dryland treatment were small”
t0“wheat”
Claim · model-written summary
The authors call for experiments on interactive elevated-CO2, water, and temperature effects to resolve model discrepancies.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- Further experimental work on the interactive effects of eCO 2 , water and temperaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Further experimental work on the interactive effects of eCO 2 , water and temperature is required to resolve these model discrepancies”
t0“wheat”
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