Figure legends
Fig. 1. Geographic coordinates and maps showing of the split-plot design in this experiment. WN, withdrawal of N fertilizer; CU, farmer’s conventional urea fertilizing practice with the thrice-split application; CB1, single-dose application of bulk blending urea (BBU) with the conventional amount of N; CB2, twice-split application of BBU with the conventional amount of N; RB1, single-dose application of BBU with 20% reduction of N; and RB2, twice-split application of BBU with 20% reduction of N.
Fig. 2. Grain yields (a) and nitrogen agronomic efficiencies (NAE, b) of rice and wheat as affected by crop rotation and fertilization. Different lowercase letters present the statistical differences among different treatments at P < 0.05 according to the least significant difference (LSD) method.
Fig. 3. Dynamics of soil total inorganic N contents (a) and plant N contents (b) at various growth stages under different treatments. Rice2019, rice growth season in 2019; Wheat, wheat growth season from 2019 to 2020; Rice2020, rice growth season in 2020.
Fig. 4. Changes in soil pH (a), soil organic carbon (SOC, b), total N (TN, c), and permanganate oxidize carbon (POXC, d) after different treatments. Different lowercase letters present the statistical differences among different treatments at P< 0.05 according to the least significant difference (LSD) method.
Fig. 5. PLSR (a, b) and PCA (c, d) analyses of soil FTIR-PAS (a, c) and FTIR-ATR (b, d) spectra. The bar codes under the spectral curves show wavenumbers of the top 10% spectral variables according to the scores of variables important in projections in the PLSR model. The density curves along the axis show the independent distributions of the first and second components under different fertilizations.R2 values represent the independent and interactional effects of crop rotation and fertilization according to the two-way permutational multivariate analysis of variance (PERMANOVA). Significance levels are denoted with * P < 0.05, **P < 0.01, and *** P < 0.001, respectively.
Fig. 6. Comparison of the intensities of soil FTIR-PAS bands as affected by different treatments. Significance levels are denoted with *P < 0.05, ** P < 0.01, and *** P< 0.001, respectively according to paired-samples T-test.
Fig. 7. Structural equation modeling shows the effects of fertilization, and soil properties on the grain yield and NAE under different crop rotation patterns. Green lines indicate positive effects, while red lines indicate negative effects. Gray lines indicate nonsignificant effects. The width of arrows indicates the strength of significant standardized path coefficients. Soil nutrients include soil total nitrogen (TN), NH4+-N, NO3-N, available phosphorus (AP), available potassium (AK), and available- Ca, Mg, Mn, Fe, Cu, Zn.
Supplementary materials
Table S1. Two-way ANOVA analysis of the crop rotation (R) and fertilization (F) on grain yield and NAE of paddy rice 2020 growing season.
Table S2. Dynamics of soil total inorganic nitrogen contents in different crop growing periods under various treatments.
Table S3. Two-way ANOVA analysis the crop rotation (R) and fertilization (F) on soil total inorganic nitrogen contents in 2019 and 2020 growing seasons.
Table S4. Dynamics of plant nitrogen contents in different crop growing periods under various treatments.
Table S5. Two-way ANOVA analysis of the crop rotation (R) and fertilization (F) on plant nitrogen contents in 2019 and 2020 growing seasons.
Table S6. Two-way ANOVA analysis the crop rotation (R) and fertilization (F) on the change of soil properties after 2019 and 2020 growing seasons.
Fig. S1. Comparison of soil pH (a), soil organic carbon (SOC, b), total nitrogen (TN, c), and permanganate oxidizes carbon (POXC, d) between before and after treatments. Significance levels are denoted with * P < 0.05, ** P < 0.01, and ***P < 0.001, respectively according to paired-samples T-test.
Fig. S2. Comparison of soil available medium and trace elements between before and after treatments. Significance levels are denoted with * P < 0.05, ** P < 0.01, and ***P < 0.001, respectively according to paired-samples T-test.
Fig. S3. Pearson correlations between various soil properties. Significance levels are denoted with * P < 0.05, **P < 0.01, and *** P < 0.001, respectively.
Fig. S4. The first (PC1) and second (PC2) loadings in PCA of differential spectra as changed by wavenumber.
Fig. S5. Comparison of the intensities of soil FTIR-PAS bands as affected by different treatments. Significance levels are denoted with * P < 0.05, ** P < 0.01, and ***P < 0.001, respectively according to paired-samples T-test.
Fig. S6. Comparison of the intensities of soil FTIR-ATR bands as affected by different treatments. Significance levels are denoted with * P < 0.05, ** P < 0.01, and ***P < 0.001, respectively according to paired-samples T-test.