Bradley Ridoutt1,2, Jing Huang3,4. 1. Commonwealth Scientific and Industrial Research Organisation (CSIRO), Agriculture and Food , Clayton South , Victoria 3169 , Australia. 2. University of the Free State , Department of Agricultural Economics , Bloemfontein 9300 , South Africa. 3. College of Life Science and Engineering , Southwest University of Science and Technology (SWUST) , Mianyang 621010 , China. 4. Institute of Environmental Sciences (CML) , Leiden University , 2333 CC Leiden , The Netherlands.