Our Goal With increasing population and climate change the ability to maximize crop production is essential We want to be able to predict optimal management practices for a variety of situations including under environmental stresses such as during a drought while minimizing pollution from un ID: 623357
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Slide1
Optimizing Crop Management Practices with DSSATSlide2
Our Goal
With increasing population and climate change, the ability to maximize crop production is essential.
We want to be able to predict optimal management practices for a variety of situations, including under environmental stresses such as during a drought, while minimizing pollution from unused fertilizer.
We will use DSSAT to simulate crop growth under a range of management practices and determine the combination that produces the largest yield with the smallest nitrogen pollution.
Find areas of DSSAT that can be improved.Slide3
Sensitivity Analysis
Variables examined:
Days between irrigations
1 – 14 in increments of 1, 15 to 21 in increments of 3
Total amount of water applied in irrigations throughout the growing season
200 to 500 mm in increments of 10
Number of applications of Nitrogen as fertilizer
0 to 3 in increments of 1
Total amount of nitrogen applied throughout the growing season
50 to 290 kg/ha in increments of 10, 300 to 400 in increments of 50
Number of applications of Phosphorus as fertilizer
0 to 2 in increments of 1
Total amount of phosphorus applied throughout the growing season
5 to 20 kg/ha in increments of 5, 40 to 100 in increments of 20Slide4
Sensitivity Analysis
Maize simulated in Ghana without precipitation
Planting date: June 17, 2004
Harvest date: September 6, 2004Slide5
Sensitivity AnalysisSlide6
Sensitivity AnalysisSlide7
Sensitivity AnalysisSlide8
Harvest: 7860 kg/ha
Water amount: 320 mm
Days between irrigations: 5
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Optimal conditions:Slide9
Harvest: 4160 kg/ha
Water amount: 200 mm
Days between irrigations: 5
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Under-watered conditions:Slide10
Harvest: 6375 kg/ha
Water amount: 500 mm
Days between irrigations: 5
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Overwatered conditions:Slide11
Harvest: 6198 kg/ha
Water amount: 320 mm
Days between irrigations: 15
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Infrequently watered conditions:Slide12
Harvest: 5918 kg/ha
Water amount: 320 mm
Days between irrigations: 5
N applied: 100 kg
N applications: 3
P applied: 40 kg
P applications: 2
Sensitivity Analysis
Fertilizer deprived conditions:Slide13
Harvest: 4160 kg/ha
Water amount: 200 mm
Days between irrigations: 5
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Under-watered conditions:Slide14
Effects of Water Deficiency
Optimal Conditions
Under-watered ConditionsSlide15
Effects of Water Deficiency
Optimal Conditions
Under-watered ConditionsSlide16
Harvest: 6375 kg/ha
Water amount: 500 mm
Days between irrigations: 5
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Overwatered conditions:Slide17
Effects of Over-watering
Optimal Conditions
Over-watered ConditionsSlide18
Effects of Water Deficiency
Optimal Conditions
Over-watered ConditionsSlide19
Harvest: 6198 kg/ha
Water amount: 320 mm
Days between irrigations: 15
N applied: 200 kg
N applications: 3
P applied: 80 kg
P applications: 2
Sensitivity Analysis
Infrequently watered conditions:Slide20
Effects of Watering Too Infrequently
Optimal Conditions
Infrequently watered ConditionsSlide21
Optimal Conditions
Infrequently watered Conditions
Effects of Watering Too InfrequentlySlide22
Harvest: 5918 kg/ha
Water amount: 320 mm
Days between irrigations: 5
N applied: 100 kg
N applications: 3
P applied: 40 kg
P applications: 2
Sensitivity Analysis
Fertilizer deprived conditions:Slide23
Effects of Fertilizer Deficiency
Optimal Conditions
Fertilizer Deprived ConditionsSlide24
Effects of Fertilizer Deficiency
Optimal Conditions
Fertilizer Deprived ConditionsSlide25
LAI vs harvest
Days between irrigations
Linear fit: LAI = 0.85858 + 0.00034544*harvest
R squared value: 0.729Slide26
Unused nitrogen vs harvest
Unused nitrogen = nitrogen applied in fertilizer – cumulative nitrogen uptakeSlide27
Conclusion
Performed exhaustive sensitivity analysis across six degrees of freedom. This can be used to help identify optimal management practice strategies.
These simulations and optimizations can be reproduced with different crop types, weather information, and soil properties.
Can help identify weaknesses in DSSAT – for example, LAI values seem to be off.Slide28
Mysteries of DSSAT
Why does overwatering reduce yield?
Water pushes nutrients deeper into the soil faster than roots can grow down?
Why is there a spike in minimum harvest weight when nitrogen is added in two applications?
Why is there a plateau in cumulative nitrogen uptake?
Crop doesn’t need more nitrogen in that growth stage?
Why does nitrogen spontaneously appear in the top soil layer when water deprived?
Nitrogen from second layer is brought up along with water?
Why does an LAI of three seem to be the maximum attainable value?Slide29Slide30
LAI vs harvest
Days between irrigations
Days between irrigationsSlide31
Unused nitrogen vs harvest
Days between irrigations
Days between irrigations
Unused nitrogen = nitrogen applied in fertilizer – cumulative nitrogen uptakeSlide32
1,5Slide33
Sensitivity AnalysisSlide34
Sensitivity AnalysisSlide35
Sensitivity Analysis