Nitrogen translocation to grain in wheat under elevated carbon dioxide: Why our models need amendment

Garry J O’Leary1, Senthold Asseng2, Neil Huth3, James Nuttall1, Kirsten Barlow4, Brendan Christy4, Malcolm McCaskill5 Cassandra Walker1, Joe Panozzo1 Debra Partington5 and Glenn J Fitzgerald1,6

1 Agriculture Victoria Research, Department of Economic Development, Jobs, Transport and Resources, 110 Natimuk Road, Horsham, Victoria, 3400 garry.o’leary@ecodev.vic.gov.au gjoleary@yahoo.com

2 University of Florida, Gainesville, FL 32611-0570, USA

3 CSIRO Agriculture, Toowoomba, Qld 4350

4 Agriculture Victoria Research, Department of Economic Development, Jobs, Transport and Resources, 124 Chiltern Valley Road, Rutherglen, Vic, 3685

5 Agriculture Victoria Research, Department of Economic Development, Jobs, Transport and Resources, 915 Mount Napier Road, Hamilton, Vic, 3300

6 Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, 4 Water Street, Creswick Victoria 3363, Australia

Abstract

The effects of elevated atmospheric carbon dioxide on grain quality are well known to be generally negative for human nutrition with reduced concentration of many nutrients such as zinc, iron and proteins. Recent crop simulation models have shown satisfactory performance in terms of growth and yield against experimental data in Australia that have raised the atmospheric CO2.  However, the simulation of the reduced concentration of nitrogen whilst reflecting an apparent dilution masks some more fundamental processes that are not modelled properly.  There are over 30 wheat crop simulation models used globally to address various agronomic questions, but few model grain quality parameters.  A recent review identified that about half of the 30 models simulated grain N concentration but only two simulated the composition of protein within the grain.  The accumulation of grain N is described differently in different models, for example the popular Australian wheat crop model (APSIM-Wheat) allows the rate on N transfer to the grain N to be controlled by factors including high temperature and terminal drought. However, to date elevated CO2 does not directly influence the rate of N accumulation in the grain in APSIM-Wheat or other commonly used crop models.  To model the additional effects of elevated CO2 on grain N beyond dilution, there is a need to account for the lower demand for N translocation to grain under these conditions.  We propose a new mechanistic model that allows such demands to be altered under elevated CO2 along with other environmental factors.

Host

The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography david_marland@hotmail.com Southern Farming Systems Agriculture Victoria

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