3.2.4 Fertilizer to Crop Price Ratio
Higher fertilizer to crop price ratio can encourage farmers to use fertilizer more efficiently, thus increasing nutrient use efficiency in the cropland (Zhang et al. 2015a, Zhang et al. 2015b). Thus, we expected a positive relationship between PUE and fertilizer to crop price ratio.
Fertilizer to crop price ratio was positively related to PUE in over 84% of the countries (21 countries) with a significant relationship (Table 4). These 21 countries accounted for 47% of the global harvested area, 53% of P in harvested crops, and 65% of fertilizer P input in 2010. In the regression analysis on the global scale, the hypothesis of a positive relationship was also not rejected (Table 4). These results indicate a synergy between fertilizer to crop price ratio and PUE on the global and national scales.