Water availability moderates N2 fixation benefit from elevated [CO2]: A 2‐year free‐air CO2 enrichment study on lentil (Lens culinaris MEDIK.) in a water limited agroecosystem |
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| Authors: | Shahnaj Parvin Shihab Uddin Maryse Bourgault Ute Roessner Sabine Tausz‐Posch Roger Armstrong Garry O'Leary Glenn Fitzgerald Michael Tausz |
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| Institution: | 1. School of Ecosystem and Forest Sciences, The University of Melbourne, Creswick, Victoria, Australia;2. Department of Agronomy, Bangladesh Agricultural University, Mymensingh, Bangladesh;3. Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Creswick, Victoria, Australia;4. Northern Agricultural Research Centre, Montana State University, Havre, Montana, USA;5. School of Biosciences, The University of Melbourne, Parkville, Victoria, Australia;6. School of Biosciences, University of Birmingham, Edgbaston, Birmingham, UK;7. Department of Economic Development, Jobs, Transport and Resources, Horsham, Victoria, Australia;8. Department of Animal, Plant and Soil Sciences, La Trobe University, Bundoora, Victoria, Australia;9. Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, Birmingham, UK |
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| Abstract: | Increased biomass and yield of plants grown under elevated CO2] often corresponds to decreased grain N concentration (N]), diminishing nutritional quality of crops. Legumes through their symbiotic N2 fixation may be better able to maintain biomass N] and grain N] under elevated CO2], provided N2 fixation is stimulated by elevated CO2] in line with growth and yield. In Mediterranean‐type agroecosystems, N2 fixation may be impaired by drought, and it is unclear whether elevated CO2] stimulation of N2 fixation can overcome this impact in dry years. To address this question, we grew lentil under two CO2] (ambient ~400 ppm and elevated ~550 ppm) levels in a free‐air CO2 enrichment facility over two growing seasons sharply contrasting in rainfall. Elevated CO2] stimulated N2 fixation through greater nodule number (+27%), mass (+18%), and specific fixation activity (+17%), and this stimulation was greater in the high than in the low rainfall/dry season. Elevated CO2] depressed grain N] (?4%) in the dry season. In contrast, grain N] increased (+3%) in the high rainfall season under elevated CO2], as a consequence of greater post‐flowering N2 fixation. Our results suggest that the benefit for N2 fixation from elevated CO2] is high as long as there is enough soil water to continue N2 fixation during grain filling. |
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| Keywords: | climate change grain protein legume N acquisition (fixation vs uptake) nodule soil water |
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