Phosphorus use efficiency in agricultural systems: A comprehensive assessment through the review of national scale substance flow analyses

This paper redefined the agricultural production system and its subsystems with respect to phosphorus (P) flow to improve the assessment of the phosphorus use efficiency (PUE), which is a key indicator for P security and sustainability of water resources. It also assessed the key P inflows, outflows, and PUE in the crop-pasture subsystem, livestock subsystem and the overall agricultural production system to present a comparative picture for these systems across various nations. PUE in the overall agricultural production system (averaged as 46% for the selected thirteen nations) is lower compared to the crop-pasture subsystem (averaged as 72%) but is higher than the livestock subsystem (averaged as 18%). Nations with high PUE in the crop-pasture subsystems usually showed high PUE in the overall agricultural production system. The proportional contribution of the livestock subsystem to the PUE of the overall agricultural production system is substantially higher than the crop-pasture subsystem for a number of EU countries (e.g., Netherlands (85%), Norway (84%), Switzerland (80%)), while the contribution of the crop-pasture subsystem is higher for some Asian countries (e.g., Bangladesh (93%) and India (87%)) and USA (80%). This study indicates that there is a high potential for improving PUE in the agricultural production system of Asian countries particularly through diverting manure-bound P from non-agricultural land or unproductive use to agricultural lands. This study suggests that shifting more towards crop production for plant-based food from animal feed/pasture production for animal-based food (meat) could improve PUE in the agricultural production system. Knowledge gaps identified and limitations addressed in this study could be useful for improving future national scale substance flow analyses (SFAs) of P for the better assessment of P flow and PUE in the agricultural production system.