Experimental data were collected from 20 long-term field experiments (22- to 33-year duration) conducted on either upland soils (wheat or maize) or on paddy-upland rotation soils (rice-wheat rotation) across the major agricultural zones in China (Figure 1). The climates at these sites changed from arid to semihumid and from cold to subtropical zone, with the annual mean temperature ranging from 1.5 °C in the northeast to 18.3 °C in the southern region, the annual precipitation ranging from 131 mm in the northwest to 1,653 mm in the southern regions, and the evaporation 0.4–6.9 times greater than the precipitation (Figure 2). The single-cropping (monoculture) trial sites (n = 5) were significantly cooler (1.54–7.78 °C) and drier (131–633 mm) than the double-cropping sites (n = 12) and paddy-upland rotation sites (n = 4; 12.8–18.3 °C and 484–1,650 mm; Figure 2). Field trial sites represented the major arable soil types within the northeast (Haplic Phaeozems and Luvic Phaeozems), northwest (Yermic Calcisol, Irragric Anthrosol, Calci-Anthric Kastanozem, and Cumulic Anthrosol), North China Plain (Fluvic Cambisol, Calcic Vertisol, Haplic Luvisol, and Terric Anthrosol), and southern (Ferrc Acrisol, Ferric Luvisol, Hydragric Anthrosol, Haplic Cambisol, and Calcaric Cambisol) regions of China.

Experimental data were collected from 20 long-term field experiments (22- to 33-year duration) conducted on either upland soils (wheat or maize) or on paddy-upland rotation soils (rice-wheat rotation) across the major agricultural zones in China (Figure 1). The climates at these sites changed from arid to semihumid and from cold to subtropical zone, with the annual mean temperature ranging from 1.5 °C in the northeast to 18.3 °C in the southern region, the annual precipitation ranging from 131 mm in the northwest to 1,653 mm in the southern regions, and the evaporation 0.4–6.9 times greater than the precipitation (Figure 2). The single-cropping (monoculture) trial sites (n = 5) were significantly cooler (1.54–7.78 °C) and drier (131–633 mm) than the double-cropping sites (n = 12) and paddy-upland rotation sites (n = 4; 12.8–18.3 °C and 484–1,650 mm; Figure 2). Field trial sites represented the major arable soil types within the northeast (Haplic Phaeozems and Luvic Phaeozems), northwest (Yermic Calcisol, Irragric Anthrosol, Calci-Anthric Kastanozem, and Cumulic Anthrosol), North China Plain (Fluvic Cambisol, Calcic Vertisol, Haplic Luvisol, and Terric Anthrosol), and southern (Ferrc Acrisol, Ferric Luvisol, Hydragric Anthrosol, Haplic Cambisol, and Calcaric Cambisol) regions of China.