title: Elevated atmospheric [CO2 ] can dramatically increase wheat yields in semi-arid environments and buffer against heat waves.
abstract: Wheat production will be impacted by increasing concentration of atmospheric CO2 [CO2 ], which is expected to rise from about 400 μmol mol(-1) in 2015 to 550 μmol mol(-1) by 2050. Changes to plant physiology and crop responses from elevated [CO2 ] (e[CO2 ]) are well documented for some environments, but field-level responses in dryland Mediterranean environments with terminal drought and heat waves are scarce. The Australian Grains Free Air CO2 Enrichment facility was established to compare wheat (Triticum aestivum) growth and yield under ambient (~370 μmol(-1) in 2007) and e[CO2 ] (550 μmol(-1) ) in semi-arid environments. Experiments were undertaken at two dryland sites (Horsham and Walpeup) across three years with two cultivars, two sowing times and two irrigation treatments. Mean yield stimulation due to e[CO2 ] was 24% at Horsham and 53% at Walpeup, with some treatment responses greater than 70%, depending on environment. Under supplemental irrigation, e[CO2 ] stimulated yields at Horsham by 37% compared to 13% under rainfed conditions, showing that water limited growth and yield response to e[CO2 ]. Heat wave effects were ameliorated under e[CO2 ] as shown by reductions of 31% and 54% in screenings and 10% and 12% larger kernels (Horsham and Walpeup). Greatest yield stimulations occurred in the e[CO2 ] late sowing and heat stressed treatments, when supplied with more water. There were no clear differences in cultivar response due to e[CO2 ]. Multiple regression showed that yield response to e[CO2 ] depended on temperatures and water availability before and after anthesis. Thus, timing of temperature and water and the crop's ability to translocate carbohydrates to the grain postanthesis were all important in determining the e[CO2 ] response. The large responses to e[CO2 ] under dryland conditions have not been previously reported and underscore the need for field level research to provide mechanistic understanding for adapting crops to a changing climate.
authors.affiliation: Victorian Department of Economic Development, Jobs, Transport and Resources, Private Bag 260, Horsham, Vic., 3401, Australia.
authors.forename: Glenn J
authors.initials: GJ
authors.lastname: Fitzgerald
authors.affiliation: Department of Forest and Ecosystem Science, The University of Melbourne, 4 Water Street, Creswick, Vic., 3363, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Tausz
authors.affiliation: Victorian Department of Economic Development, Jobs, Transport and Resources, Private Bag 260, Horsham, Vic., 3401, Australia.
authors.forename: Garry
authors.initials: G
authors.lastname: O'Leary
authors.affiliation: Victorian Department of Economic Development, Jobs, Transport and Resources, Private Bag 260, Horsham, Vic., 3401, Australia.
authors.forename: Mahabubur R
authors.initials: MR
authors.lastname: Mollah
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 4 Water Street, Creswick, Vic., 3363, Australia.
authors.forename: Sabine
authors.initials: S
authors.lastname: Tausz-Posch
authors.affiliation: Centre for Crop Health, University of Southern Queensland, Toowoomba, Qld, 4350, Australia.
authors.forename: Saman
authors.initials: S
authors.lastname: Seneweera
authors.affiliation: Victorian Department of Economic Development, Jobs, Transport and Resources, Private Bag 260, Horsham, Vic., 3401, Australia.|Dodgshun Medlin Agricultural Management, 348 Campbell St, Swan Hill, Vic., 3585, Australia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Mock
authors.affiliation: Department of Forest and Ecosystem Science, The University of Melbourne, 4 Water Street, Creswick, Vic., 3363, Australia.
authors.forename: Markus
authors.initials: M
authors.lastname: Löw
authors.affiliation: Victorian Department of Economic Development, Jobs, Transport and Resources, Hamilton Centre, Mount Napier Road, Hamilton, Vic., 3300, Australia.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Partington
authors.affiliation: Tasmanian Institute of Agriculture, Private Bag 98, Hobart, Tas., 7001, Australia.
authors.forename: David
authors.initials: D
authors.lastname: McNeil
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 4 Water Street, Creswick, Vic., 3363, Australia.|International Plant Nutrition Institute, 54 Florence St, Horsham, Vic., Australia.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Norton
mesh_terms: D057914:Agricultural Irrigation / Q000379:methods; D001272:Atmosphere / Q000032:analysis; D018533:Biomass; D002245:Carbon Dioxide / Q000032:analysis*; D055864:Droughts; D002523:Edible Grain / Q000254:growth & development; D004784:Environmental Monitoring; D006358:Hot Temperature; D011891:Rain; D014908:Triticum / Q000254:growth & development*; D014739:Victoria; D014867:Water
chemical_list: D014867:Water; D002245:Carbon Dioxide
keywords: Australian Grains Free Air CO2 Enrichment; Free Air CO2 Enrichment; dryland; elevated CO2; heat wave; wheat; yield