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Sustainable crop intensification: Capturing opportunities in a highly variable climate with relay crops

Joseph X Eyre1, John P Dimes1, Howard Cox1 and Daniel Rodriguez2

1Agri-Science Queensland, Department of Agriculture, Fisheries & Forestry (DAFF), PO Box 102, Toowoomba, Qld 4350 Australia.

2 Queensland Alliance for Agriculture and Food Innovation (QAAFI), University of Queensland, St Lucia, Qld 4072 Australia

Abstract

Rainfall in Australia’s northern grains region is mostly summer dominant and highly variable driving the high variability in grain yield. Efficient capture and utilisation of rainfall is essential for future increases in production per unit land, to mitigate food insecurity and to increase return on investment. However, agronomic decisions such as plant population, row width and cultivar selection typically target initial plant available water and median to sub-median in-crop rainfall with a view to manage economic risk. Subsequently maximum yield potentials are limited, weeds can proliferate, soil may erode and sub-potential economic returns are achieved in seasons with above average in-crop rainfall. Experiments on maize-mungbean cropping systems in Queensland indicate that sowing mungbean opportunistically into standing post-anthesis maize (i.e. relay cropping) in high rainfall seasons can increase productivity. Importantly the opportunistic mungbean crop did not influence the yield of the primary maize crop. Intra-specific competition decreased as relay crops were sown at progressively later maize phenological stages and consequently mungbean yields increased. Mungbean relay sown into post-anthesis maize produced similar or higher yields than sole cropped mungbeans. We propose that the basis of yield gains observed in this maize-mungbean cropping system could similarly be adapted to a biologically and mechanically feasible wheat-legume relay cropping system for the northern grains region.

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