Irrigation constraints shape the global potential for multiple cropping expansion on existing cropland

Multiple cropping increases land productivity by allowing multiple harvests per year, offering production gains without cropland expansion. Irrigation is especially critical in the seasonally dry tropics, enabling multiple cropping where otherwise only a single rainfed cycle would be feasible. Estimates of the current state of multiple cropping and the multiple cropping expansion potential without changes in irrigation patterns exist, but the multiple cropping expansion potential through irrigation expansion has not yet been assessed at the global scale. Here, we estimate multiple cropping expansion potentials on existing cropland considering the interaction with irrigation and local water availability constraints to determine how much cropland area can be managed in multiple cropping systems and the associated increases in annual yields and crop production. We find that, under current climatic conditions, there is considerable global biophysical potential to expand multiple cropping on existing cropland, particularly when also expanding irrigation. Total global crop production could increase by 28% (from 4 200 mio. t DM to 5 400 mio. t DM). This gain stems from nearly quadrupling the area under rainfed multiple cropping, more than doubling multiple cropping area within already irrigated lands, and expanding irrigation into areas where it facilitates another growing season. Our study reveals a considerable multiple cropping expansion potential on existing cropland that-when tapped-could contribute to averting further cropland expansion to meet future demand for agricultural outputs. Local irrigation water availability constrains the irrigation-enabled multiple cropping potential, implying that the interaction of multiple cropping and irrigation is crucial to consider in comprehensive land and water assessments that account for biophysical and socio-economic constraints, sustainability criteria, and land competition under future global change.