title: Response of wheat growth, grain yield and water use to elevated CO2under a Free-Air CO2Enrichment (FACE) experiment and modelling in a semi-arid environment.
abstract: The response of wheat crops to elevated CO2(eCO2) was measured and modelled with the Australian Grains Free-Air CO2Enrichment experiment, located at Horsham, Australia. Treatments included CO2by water, N and temperature. The location represents a semi-arid environment with a seasonal VPD of around 0.5 kPa. Over 3 years, the observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha-1and 1600 to 3900 kg ha-1, respectively, over various sowing times and irrigation regimes. The mean observed response to daytime eCO2(from 365 to 550 μmol mol-1CO2) 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 eCO2, 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 eCO2was 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 eCO2. However, under irrigation, the effect of late sowing on response to eCO2to biomass accumulation at DC65 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 eCO2under irrigation, but the differences compared to the dryland treatment were small. Further experimental work on the interactive effects of eCO2, water and temperature is required to resolve these model discrepancies.
authors.affiliation: Department of Environment and Primary Industries, Horsham, Vic., 3401, Australia.
authors.forename: Garry J
authors.initials: GJ
authors.lastname: O'Leary
authors.affiliation: Department of Environment and Primary Industries, Rutherglen, Vic., 3658, Australia.
authors.forename: Brendan
authors.initials: B
authors.lastname: Christy
authors.affiliation: Department of Environment and Primary Industries, Horsham, Vic., 3401, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Nuttall
authors.affiliation: CSIRO Agriculture, Toowoomba, Qld, 4350, Australia.
authors.forename: Neil
authors.initials: N
authors.lastname: Huth
authors.affiliation: University of Florida, Gainesville, FL, 32611-0570, USA.
authors.forename: Davide
authors.initials: D
authors.lastname: Cammarano
authors.affiliation: Washington State University, Pullman, WA, 99164-6120, USA.
authors.forename: Claudio
authors.initials: C
authors.lastname: Stöckle
authors.affiliation: Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Bruno
authors.initials: B
authors.lastname: Basso
authors.affiliation: Michigan State University, East Lansing, MI, 48824, USA.
authors.forename: Iurii
authors.initials: I
authors.lastname: Shcherbak
authors.affiliation: Department of Environment and Primary Industries, Horsham, Vic., 3401, Australia.
authors.forename: Glenn
authors.initials: G
authors.lastname: Fitzgerald
authors.affiliation: Plant Functional Biology & Climate Change, University of Technology Sydney, Sydney, NSW, Australia.
authors.forename: Qunying
authors.initials: Q
authors.lastname: Luo
authors.affiliation: Department of Agriculture and Forestry Western Australia, South Perth, WA, 6151, Australia.
authors.forename: Immaculada
authors.initials: I
authors.lastname: Farre-Codina
authors.affiliation: CSIRO Agriculture, Floreat, WA, 6014, Australia.|School of Plant Biology, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.
authors.forename: Jairo
authors.initials: J
authors.lastname: Palta
authors.affiliation: University of Florida, Gainesville, FL, 32611-0570, USA.
authors.forename: Senthold
authors.initials: S
authors.lastname: Asseng
keywords: climate change; elevated CO2; modelling; radiation use efficiency; transpiration efficiency