Fig. 3: Spatial distributions of the crop fertilizer increased yield (FIY) from 2009 to 2019 in SW China.

The maps show the spatial distributions of the FIY of rice in 2009 (a) and 2019 (b), the spatial distributions of the FIY of maize in 2009 (c) and 2019 (d), and the spatial distributions of the FIY of wheat in 2009 (e) and 2019 (f). The color bands denote various yield classes (t ha⁻¹). The box of the violin plot denotes the interquartile range with the median value shown as a bold line, the whiskers of the violin plot indicate the 1.5 interquartile range, and the outer border of the violin plot denotes the data distribution. The symbol t denotes the value obtained from the t-test, with the asterisk (*) indicating that the mean difference between 2009 and 2019 is statistically significant at the 0.05 confidence level.