Evaluating the yield gap of cropping systems: A comparison of alternative approaches across regions

CONTEXT Yield gap analyses at the cropping system level are key for identifying opportunities to increase crop yield and support food security globally. While several cropping systems yield gap approaches namely aggregated yield gap, individual crop yield gaps, nutritional, financial, equivalent yield gaps and relative yield gap have been applied in the literature to quantify yield gaps, no studies have reported how different approaches are related or have suggested which metrics are most appropriate for different objectives. OBJECTIVE To address this gap, we evaluated the relationships between those yield gap approaches across different farming systems in two contrasting regions: Queensland, Australia and the dry zone of Sri Lanka. METHODS We evaluated these different approaches using potential crop rotations created using wheat and sorghum in Queensland and rice and mungbean in Sri Lanka. We used the Agricultural Production Systems sIMulator (APSIM) to simulate the yield potential for each cropping system under different sowing windows, planting densities, and cultivars and actual yields were obtained from national statistics reports for the selected regions. RESULTS AND CONCLUSIONS Results revealed a strong correlation between the aggregated yield gap, equivalent yield gap, relative yield gap as well as nutritional and financial yield gaps in both farming systems. However, individual crop yield gaps do not consistently correlate with any of the other approaches suggesting that it is a limited indicator for evaluating the system as a whole in either farming system. This study suggests that the aggregated yield gap is a consistent approach to capture the cropping system performance while requiring minimal data. Relative yield gap reflects system efficiency relative to their potential, making it useful for comparing across crops or cropping systems. SIGNIFICANCE As such, aggregated yield gap is a broadly relevant, valuable yet simple metric for farmers and policymakers to use to improve productivity and food security across farming systems globally.