Affiliation: | Agriculture Canada, Research Station, Harrow, Ontario, Canada NOR 1G0;International Rice Research Institute, Agroecology Unit, POB 933,1099 Manila, Phillippines, and Department of Theoretical Production Ecology, Agricultural University, P O Box 430, 6700 AK Wageningen, The Netherlands;School of Crop Sciences, University of Sydney, New South Wales 2006, Australia |