Figure 1.
Effects of the N application rate on the economic value (EV) and N economic benefit (NEB) of flue-cured tobacco average over years. Bars labeled with different capital letters indicate a significant difference (p < 0.05) among N treatments. Error bars represent the standard error of means.
Figure 2.
Effect of the N rate on the integrate grade of chemical quality of average over years in C3F grade. Integrate grade was calculated based on Table S2 and Table S4. Different capital letters indicate significant difference among the N rates (p < 0.05). Error bars represent the standard error of means.
Figure 3.
Effect of the N rate on leaf midrib proportions of upper B2F, middle C3F and lower X2F flue-cured tobacco leaves. Different capital letters indicate significant differences among the N rates in the same grade (p < 0.05).
Figure 4.
Effect of the N rate on the average yield of superior, medium and inferior flue-cured tobacco. Different capital, lowercase and italics lowercase letters indicate the significant differences in the yields of superior tobacco, medium and inferior tobacco, respectively (p < 0.05). The classification criterion and responding sales prices of superior, medium and inferior are shown in Table S2.
Figure 5.
Correlation between the total economic value (EV) and yield of superior, medium and inferior flue-cured tobacco average over two years.
Figure 6.
Effect of the N rate on the average leaf growth rate at resetting, topping and harvesting stage average over years. Different capital letters indicate significant difference among the N rates (p < 0.05).
Figure 7.
Correlation between the yield of superior tobacco and the leaf growth rate in the prosperous stage over six N rates and two years.
Figure 8.
Nitrogen effect equation between the sum of applied N rate and the residual soil inorganic N before transplanting and economic value (EV) of flue-cured tobacco and superior tobacco yield. Two data points outside the 95% confidence were excluded for establish of the effect equation. The residual soil inorganic N content before transplanting is shown in Table S5.
Table S1.
The annual average (1981–2020) and the experimental year (2021–2022) of precipitation, mean temperature and sunshine hours during the flue-cured tobacco growing season (April–August).
| Precipitation (mm) | Temperature (°C ) | Sunshine duration (h) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Month | 1981–2020 | 2021 | 2022 | 1981–2020 | 2021 | 2022 | 1981–2020 | 2021 | 2022 |
| April | 28.0 | 64.5 | 35.6 | 18.2 | 19.2 | 16.7 | 223 | 231 | 227 |
| May | 80.1 | 22.5 | 69.8 | 20.3 | 21.8 | 18.3 | 208 | 229 | 219 |
| June | 152 | 166 | 43.8 | 21.2 | 21.9 | 21.1 | 131 | 129 | 130 |
| July | 210 | 107 | 27.6 | 21.2 | 21.5 | 22.6 | 116 | 96 | 106 |
| August | 162 | 199 | 95.4 | 21.4 | 21.5 | 22.4 | 149 | 124 | 137 |
| Average | 126 | 112 | 54.4 | 20.5 | 21.2 | 20.2 | 165 | 162 | 164 |
| Max | 268 | 199 | 95.4 | 31.8 | 33.1 | 31.1 | 241 | 231 | 227 |
| Min | 16.0 | 22.5 | 27.6 | 9.4 | 8.8 | 3.8 | 89 | 96 | 106 |
Table S2.
The standard of grading superior, medium and inferior flue-cured tobacco and their corresponding purchase price.
| Classification | Grade | Maturity | Structure | Thickness | Oil content | Chroma | Length (cm) | Mutilation (%) | Price (RMB kg−1) |
|---|---|---|---|---|---|---|---|---|---|
| Superior | B1F | Maturity | Slight loose | Slight thick | Many | Very strong | 45 | 15 | 41.4 |
| B2F | Maturity | Slight loose | Slight thick | Medium | Strong | 40 | 20 | 34.0 | |
| C1F | Maturity | Loose | Medium | Many | Very strong | 45 | 10 | 48.5 | |
| C2F | Maturity | Loose | Medium | Medium | Strong | 40 | 15 | 43.8 | |
| C3F | Maturity | Loose | Medium | Medium | Medium | 35 | 25 | 38.8 | |
| Medium | B3F | Maturity | Slight dense | Slight thick | Medium | Medium | 35 | 30 | 22.0 |
| X2F | Maturity | Loose | Slight thin | Less | Medium | 35 | 25 | 22.9 | |
| X3F | Maturity | Loose | Slight thin | Less | Weak | 30 | 30 | 11.9 | |
| X2V | Slight maturity | Loose | Slight thin | Less | Medium | 35 | 15 | 8.6 | |
| Inferior | CX1K | Slight maturity | Loose | Slight thin | Medium | — | 35 | 20 | 5.8 |
Table S3.
Effects of nitrogen N application rate on the average content of the chemical compound as intrinsic quality indexes of superior C3F tobacco leaf average over years (n = 6).
| N rate (kg N ha−1) | Nicotine (%) | Total N (%) | Reducing sugar (%) | Total sugar (%) | K (%) | Cl (%) | Total sugar / nicotine | Total N / nicotine | K / Cl |
|---|---|---|---|---|---|---|---|---|---|
| 0 | 1.40 ± 0.04 | 1.44 ± 0.01 | 21.5 ± 0.06 | 36.0 ± 0.79 | 1.43 ± 0.02 | 0.44 ± 0.04 | 30.1 ± 2.12 | 1.31 ± 0.09 | 3.43 ± 0.40 |
| 45 | 1.42 ± 0.03 | 1.51 ± 0.03 | 22.2 ± 0.47 | 36.7 ± 1.34 | 1.40 ± 0.02 | 0.47 ± 0.08 | 26.2 ± 0.72 | 1.22 ± 0.07 | 4.43 ± 0.38 |
| 60 | 1.56 ± 0.05 | 1.56 ± 0.02 | 19.8 ± 0.59 | 34.0 ± 0.91 | 1.66 ± 0.13 | 0.39 ± 0.02 | 22.2 ± 2.11 | 1.08 ± 0.06 | 4.72 ± 1.37 |
| 75 | 2.49 ± 0.07 | 2.20 ± 0.07 | 18.6 ± 0.94 | 28.1 ± 1.17 | 1.48 ± 0.07 | 0.42 ± 0.06 | 16.4 ± 0.33 | 0.79 ± 0.02 | 3.04 ± 0.06 |
| 90 | 2.38 ± 0.05 | 1.91 ± 0.08 | 20.6 ± 0.70 | 31.8 ± 0.96 | 1.40 ± 0.03 | 0.35 ± 0.04 | 12.2 ± 0.11 | 0.82 ± 0.03 | 4.42 ± 0.18 |
| 105 | 2.08 ± 0.04 | 1.72 ± 0.02 | 19.2 ± 0.08 | 31.2 ± 0.42 | 1.46 ± 0.02 | 0.37 ± 0.03 | 15.1 ± 0.77 | 0.82 ± 0.02 | 3.57 ± 0.34 |
| LSD0.05 | 0.28 | 0.23 | 2.84 | 5.59 | 0.29 | 0.27 | 6.16 | 0.31 | 2.73 |
| Best range | 2.20–2.80 | 2.00–2.50 | 18.0–22.0 | 26.0–30.0 | ≥ 2.50 | c 0.60 | 8.50–9.50 | 0.95–1.05 | ≥ 8.00 |
Table S4.
Range of chemical compound content and the corresponding grade of flue-cured tobacco style characteristics evaluation of the first most influential tobacco areas in Yunnan province – chemical composition evaluation table (C3F).
| Compound | Grading rules | ||||
|---|---|---|---|---|---|
| 100 | 100–90 | 90–80 | 80–70 | 70–60 | |
| Nicotine (%) (B1) | 2.20–2.80 | 2.20–2.00 | 2.00–1.80 | 1.80–1.70 | 1.70–1.60 |
| 2.80–2.90 | 2.90–3.00 | 3.00–3.10 | 3.10–3.20 | ||
| Total N (%) (B2) | 2.00–2.50 | 2.00–1.90 | 1.90–1.80 | 1.80–1.70 | 1.70–1.60 |
| 2.50–2.60 | 2.60–2.70 | 2.70–2.80 | 2.80–2.90 | ||
| Reducing sugar (%) (B3) | 18.0–22.0 | 18.0–16.0 | 16.0–14.0 | 14.0–13.0 | 13.0–12.0 |
| 22.0–24.0 | 24.0–26.0 | 26.0–27.0 | 27.0–28.0 | ||
| K (%) (B4) | ≥ 2.50 | 2.50–2.00 | 2.00–1.50 | 1.50–1.20 | 1.20–1.00 |
| Total sugar / Nicotine (B5) | 8.50–9.50 | 8.50–7.00 | 7.00–6.00 | 6.00–5.50 | 5.50–5.00 |
| 9.50–12.0 | 12.0–13.0 | 13.0–14.0 | 14.0–15.0 | ||
| Total N / Nicotine (B6) | 0.95–1.05 | 0.95–0.80 | 0.80–0.70 | 0.70–0.65 | 0.65–0.60 |
| 1.05–1.20 | 1.20–1.30 | 1.30–1.35 | 1.35–1.40 | ||
| K/Cl (B7) | ≥ 8.00 | 8.00–6.00 | 6.00–5.00 | 5.00–4.50 | 4.50–4.00 |
| Integrated grade (IG) | IG = B1 × 0.18 + B2 × 0.10 + B3 × 0.15 + B4 × 0.09 + B5 × 0.26 + B6 × 0.12 + B7 × 0.10 | ||||
Table S5.
Inorganic nitrogen content in 0–20 cm soil before tobacco transplanting (BefTrp) and after harvesting (AftHarv) in the experimental site (kg N ha−1).
| Time | N rate | Inorganic N | NH4+ –N | NO3− –N |
|---|---|---|---|---|
| BefTrp (April 22, 2021) | 32.0 ± 2.20 | 1.45 ± 0.65 | 30.5 ± 2.69 | |
| AftHarv (August 31, 2021) | 0 | 23.3 ± 1.37 | 0.98 ± 0.12 | 22.4 ± 1.49 |
| 45 | 25.9 ± 0.07 | 1.00 ± 0.05 | 24.9 ± 0.12 | |
| 60 | 28.1 ± 0.85 | 1.01 ± 0.11 | 27.0 ± 0.82 | |
| 75 | 31.7 ± 1.27 | 1.03 ± 0.04 | 30.7 ± 1.24 | |
| 90 | 34.8 ± 0.83 | 1.33 ± 0.26 | 33.5 ± 0.60 | |
| 105 | 47.4 ± 4.22 | 1.13 ± 0.16 | 46.3 ± 4.36 | |
| BefTrp (April 25, 2022) | 0 | 27.0 ± 3.13 | 9.81 ± 0.45 | 17.2 ± 2.93 |
| 45 | 45.7 ± 7.79 | 8.12 ± 0.24 | 37.6 ± 7.72 | |
| 60 | 54.5 ± 5.41 | 8.19 ± 0.21 | 46.3 ± 5.21 | |
| 75 | 70.6 ± 8.21 | 9.71 ± 0.33 | 60.8 ± 7.90 | |
| 90 | 73.3 ± 10.4 | 9.21 ± 1.54 | 64.1 ± 10.0 | |
| 105 | 80.7 ± 1.14 | 9.79 ± 1.09 | 70.9 ± 2.23 | |
| AftHarv (September 05, 2022) | 0 | 21.0 ± 6.65 | 2.58 ± 0.40 | 18.5 ± 6.57 |
| 45 | 56.2 ± 7.92 | 7.75 ± 0.42 | 48.4 ± 7.82 | |
| 60 | 62.9 ± 8.98 | 12.1 ± 2.71 | 50.8 ± 7.35 | |
| 75 | 76.3 ± 9.50 | 6.80 ± 0.29 | 69.5 ± 9.23 | |
| 90 | 90.4 ± 9.17 | 7.04 ± 1.54 | 83.4 ± 7.92 | |
| 105 | 97.7 ± 7.66 | 7.29 ± 2.40 | 90.4 ± 7.12 |
Table S6.
Recommendation of the optimal total N application rate, and the N rate as base fertilizer at resetting and as topdressing at prosperous growth stage according to the soil inorganic N content before transplanting and nitrogen effect equation, and nitrogen application amount.
| Recommend N rate | |||
|---|---|---|---|
| Soil N min (kg N ha−1) | Total (kg N ha−1) | Base fertilizer (kg N ha−1) | Top application (kg N ha−1) |
| 20 | 110 | 44 | 66 |
| 30 | 100 | 40 | 60 |
| 40 | 90 | 36 | 54 |
| 50 | 80 | 32 | 48 |
| 60 | 70 | 28 | 42 |
| 70 | 60 | 24 | 36 |
| 80 | 50 | 15 | 35 |
| 90 | 40 | 5 | 35 |
| 100 | 30 | 0 | 30 |