Figure 1.
Map of the study area
Abbildung 1. Karte des Untersuchungsgebiets
Figure 2.
Distribution of average monthly rainfall and temperature across the study area
Abbildung 2. Verteilung des durchschnittlichen monatlichen Niederschlags und der Temperatur im Untersuchungsgebiet
Table 1.
Information about seeds, fertilizer rate, and irrigation water in the study area
Tabelle 1. Informationen zu Saatgut, Düngermenge und Bewässerungswasser im Untersuchungsgebiet
| Crop | Seeds (kg/ha) | Fertilizer rate (kg/ha) | Rain fed (mm) | Required irrigation (mm) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| IS | DS | MS | LS | IS | DS | MS | LS | IS | DS | MS | LS | ||
| WS | 80 | 60 | 100 | 50 | 130 | 33.4 | 188.2 | 34.7 | 25.6 | 50 | 18 | 60 | 50 |
| Stf | 100 | 70 | 100 | 60 | 140 | 46.4 | 73.7 | 192.3 | 306.5 | 40 | 45 | 10 | 0 |
[i] IS: initial stage; DS: development stage; MS: middle stage; LS: late stage
Table 2.
The physical and chemical properties of soil across the study area
Tabelle 2. Die physikalischen und chemischen Eigenschaften des Bodens im gesamten Untersuchungsgebiet
| Variables | Soil depth layers (cm) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ha Tien | Kien Luong | Rach Gia | ||||||||||
| Layer | 0–10 | 10–20 | 20–30 | 30–40 | 0–10 | 10–20 | 20–30 | 30–40 | 0–10 | 10–20 | 20–30 | 30–40 |
| Sand (%) | 24.5 | 27.6 | 22.7 | 19.4 | 25.7 | 27.9 | 24.8 | 19.7 | 22.7 | 24.1 | 24.8 | 19.8 |
| Silt (%) | 60.7 | 55.8 | 51.9 | 48.7 | 55.2 | 51.8 | 53.8 | 51.1 | 51.9 | 48.7 | 55.4 | 52.3 |
| Clay (%) | 14.8 | 16.6 | 25.4 | 31.9 | 19.1 | 20.3 | 21.4 | 29.2 | 25.4 | 27.2 | 19.8 | 27.9 |
| Soil features | Silty clay loam | Silt loam | Silty clay loam | Silty clay loam | Silt loam | Silt loam | Silt loam | Silty clay Loam | Silt loam | Silt loam | Silt loam | Silty clay loam |
| FC (% vol) | 40 | 39 | 42 | 38 | 33 | 33 | 33 | 44 | 33 | 33 | 33 | 44 |
| PWP (% vol) | 22 | 18 | 19 | 19 | 13 | 13 | 13 | 23 | 13 | 13 | 13 | 23 |
| SAT (% vol) | 52 | 46 | 52 | 52 | 46 | 46 | 46 | 52 | 46 | 46 | 46 | 52 |
| BD (g/cm3) | 1.12 | 1.21 | 1.25 | 1.31 | 0.98 | 0.89 | 0.96 | 1.02 | 0.97 | 0.94 | 0.99 | 1.13 |
| TAW (mm/m) | 210 | 200 | 210 | 210 | 200 | 200 | 200 | 210 | 200 | 200 | 200 | 210 |
| K+ (cmol/kg) | 0.21 | 0.18 | 0.18 | 0.17 | 0.19 | 0.18 | 0.19 | 0.22 | 0.19 | 0.18 | 0.18 | 0.20 |
| Na+ (cmol/kg) | 0.13 | 0.12 | 0.11 | 0.12 | 0.10 | 0.12 | 0.13 | 0.14 | 0.11 | 0.12 | 0.12 | 0.14 |
| Ca2+ (cmol/kg) | 3.6 | 3.8 | 3.2 | 3.3 | 3.7 | 3.6 | 3.8 | 3.9 | 3.8 | 3.7 | 3.9 | 4.0 |
| Mg2+ (cmol/kg) | 0.95 | 0.84 | 0.79 | 0.92 | 0.83 | 0.85 | 0.86 | 0.99 | 0.84 | 0.86 | 0.82 | 0.97 |
| pH (H2O) | 5.5 | 5.3 | 5.6 | 5.7 | 5.7 | 5.4 | 5.1 | 5.0 | 5.8 | 5.5 | 5.6 | 5.0 |
[i] FC: field capacity; PWP: permanent wilting point; SAT: saturated hydraulic conductivity; BD: bulk density; TAW: total available soil water
Figure 3.
Meteorology variations applied for the validation and calibration procedures of the model
Abbildung 3. Meteorologische Variationen, die für die Validierungs- und Kalibrierungsverfahren des Modells angewendet werden
Table 3.
The main parameters used to simulate the crop cultivation schedules
Tabelle 3. Die wichtigsten Parameter zur Simulation der Anbaupläne für Pflanzen
| Description | Default | Selected |
|---|---|---|
| Base temperature | 5.0 | 4.80 |
| Cut-off temperature | 30 | 28.6 |
| Canopy cover per seedling at 90% emergence (CCo) | 5.00 | 4.85 |
| Soil water depletion threshold for stomata control – upper | 0.50 | 0.48 |
| Shape factor for water stress coefficient for canopy senescence | 3.00 | 2.90 |
| Decline in crop coefficient after reaching maximum canopy cover | 0.3% | 0.3% |
| Crop coefficient for transpiration at CC (100%) | 1.00 | 0.95 |
| Leaf growth stress coefficient curve shape | 3.0 | 2.84 |
| Normalized water productivity (WP) | 15% | 14.6% |
| Allowable maximum increase (%) of specified HI | 10 | 9.4 |
Table 4.
Comparison of observed rice grain yields with the simulated results
Tabelle 4. Vergleich der beobachteten Reiskornerträge mit den simulierten Ergebnissen
| Year | Model validation | Year | Model calibration | ||
|---|---|---|---|---|---|
| Observed | Simulated | Observed | Simulated | ||
| 2000 | 7.10 | 6.98 | 2011 | 6.64 | 6.68 |
| 2001 | 7.26 | 7.14 | 2012 | 7.12 | 6.86 |
| 2002 | 6.42 | 6.31 | 2013 | 7.28 | 7.16 |
| 2003 | 6.54 | 6.77 | 2014 | 6.57 | 6.83 |
| 2004 | 6.72 | 6.82 | 2015 | 6.13 | 6.29 |
| 2005 | 6.35 | 6.57 | 2016 | 6.44 | 6.39 |
| 2006 | 6.97 | 6.76 | 2017 | 7.25 | 7.34 |
| 2007 | 7.13 | 6.96 | 2018 | 7.34 | 6.99 |
| 2008 | 7.35 | 7.27 | 2019 | 6.35 | 6.48 |
| 2009 | 7.58 | 7.51 | 2020 | 6.78 | 6.85 |
| 2010 | 6.83 | 6.98 | 2021 | 7.40 | 7.35 |
Figure 4.
Performance of model in calibration and validation procedures
Abbildung 4. Leistung des Modells bei Kalibrierungs- und Validierungsverfahren
Table 5.
The calibration and validation results of rice grain yield corresponding to winter–spring and summer–fall vegetation seasons
Tabelle 5. Die Kalibrierungs- und Validierungsergebnisse des Reiskornertrags entsprechen den Vegetationsperioden Winter-Frühling und Sommer-Herbst
| Crop | Validation | Calibration | ||||||
|---|---|---|---|---|---|---|---|---|
| d | R2 | RMSE | MAE | d | R2 | RMSE | MAE | |
| WS | 0.83 | 0.83 | 0.17 | 14.9% | 0.86 | 0.85 | 0.11 | 12.6% |
| SF | 0.76 | 0.77 | 0.21 | 17.6% | 0.78 | 0.79 | 0.16 | 13.4% |
Figure 5.
Rice grain yield response to climate variables by shifting the crop cultivation schedules (sowing date) for a) winter–spring vegetation season and b) summer–fall vegetation season
Abbildung 5. Reaktion des Reiskornertrags auf Klimavariablen durch Verschiebung der Anbaupläne (Aussaatdatum) für a) Winter-Frühjahr-Vegetationsperiode und b) Sommer-Herbst-Vegetationsperiode
Table 6.
Rice grain yield response to change in the crop cultivation schedules (sowing date) in the winter–spring and summer–fall vegetation seasons
Tabelle 6. Reaktion des Reiskornertrags auf Änderungen der Anbaupläne (Aussaattermin) in der Winter-Frühlings- und Sommer-Herbst-Vegetationsperioden
| Sowing date | Winter–spring | Period | Summer–fall | ||
|---|---|---|---|---|---|
| Rice grain yield (ton/ha) | Changed trend (%) | Rice grain yield (ton/ha) | Changed trend (%) | ||
| Current | 7.4 | - | Current | 6.5 | - |
| 30 | 7.3 | −1.6 | 30 | 6.6 | 1.9 |
| 25 | 7.1 | −3.8 | 25 | 6.7 | 2.7 |
| 20 | 6.9 | −6.7 | 20 | 6.9 | 5.6 |
| 15 | 7.0 | −5.4 | 15 | 6.7 | 2.5 |
| 10 | 7.0 | −4.9 | 10 | 6.6 | 1.3 |
| 5 | 7.2 | −2.1 | 5 | 6.4 | −0.8 |
| −5 | 7.5 | 0.9 | −5 | 6.3 | −2.4 |
| −10 | 7.6 | 2.3 | −10 | 6.3 | −3.7 |
| −15 | 7.8 | 5.7 | −15 | 6.1 | −5.8 |
| −20 | 8.0 | 7.8 | −20 | 6.2 | −3.9 |
| −25 | 7.7 | 4.3 | −25 | 6.4 | −1.6 |
| −30 | 7.5 | 1.1 | −30 | 6.5 | 0.5 |