2.3 Projection of Future PUE and Phosphorus Budget
We projected future PUE and P budget for crop production in three PUE
improvement scenarios (Table 2): 1) the Business-As-Usual (BAU)
scenario, 2) the Moderate-Policy-Ambition (MPA) scenario, and 3) the
High-Policy-Ambition (HPA) scenario. From scenario BAU to HPA, we assume
that PUE by country and crop type would have no improvement, median
improvement, and significant improvement, respectively. To decide the
improvement level, we first calculated the PUE by crop type of 12
regions (Table S17) in 2010 (the average of 2005-2014). Then for each
crop type, we set the median and 75th percentile value
of the 12 regions’ PUE as the minimum PUE level to achieve in MPA and
HPA scenarios, respectively.
Table 2 The settings of three PUE improvement scenarios and
three cases of P fertilizer to total inputs ratio from 2014 to 2050.