Spatial Variation in Corn and Soybean Fields in Central Iowa
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Spatial Variation in Spatial Variation in Corn and Soybean Corn and Soybean Fields in Central Fields in Central Iowa Iowa Energy Balance Energy Balance and Carbon and Carbon Dioxide Dioxide Exchanges Exchanges
description
Spatial Variation in Corn and Soybean Fields in Central Iowa. Energy Balance and Carbon Dioxide Exchanges. Authors. J.L. Hatfield J.H. Prueger W.P. Kustas. Background. Experiment conducted in central Iowa during 2002 as part of the Soil Moisture experiment (SMEX02) - PowerPoint PPT Presentation
Transcript of Spatial Variation in Corn and Soybean Fields in Central Iowa
Spatial Variation in Corn and Spatial Variation in Corn and Soybean Fields in Central Soybean Fields in Central
Iowa Iowa Energy Balance and Energy Balance and
Carbon Dioxide Carbon Dioxide
ExchangesExchanges
AuthorsAuthors
J.L. HatfieldJ.L. Hatfield
J.H. PruegerJ.H. Prueger
W.P. KustasW.P. Kustas
BackgroundBackground
Experiment conducted in central Experiment conducted in central Iowa during 2002 as part of the Soil Iowa during 2002 as part of the Soil Moisture experiment (SMEX02)Moisture experiment (SMEX02)
Opportunity to combine a Soil Opportunity to combine a Soil Moisture Atmospheric Coupling Moisture Atmospheric Coupling Experiment (SMACEX) to quantify the Experiment (SMACEX) to quantify the spatial variation in energy balance spatial variation in energy balance and carbon dioxide exchanges across and carbon dioxide exchanges across a watersheda watershed
ObjectivesObjectives
Quantify the differences among Quantify the differences among energy balance and COenergy balance and CO22 exchanges exchanges across multiple sites in a corn-across multiple sites in a corn-soybean areasoybean area
Quantify the differences among sites Quantify the differences among sites caused by soil and crop growth caused by soil and crop growth differencesdifferences
SiteSite
Walnut Creek WatershedWalnut Creek Watershed
5200 ha corn/soybean production 5200 ha corn/soybean production area in central Iowaarea in central Iowa
Soils within Fields Soils within Fields
Eight sites were in Clarion soilEight sites were in Clarion soil
Two sites in Nicollet soilTwo sites in Nicollet soil
Two sites in Webster soilTwo sites in Webster soil
Differences among these soils is due Differences among these soils is due to soil water holding capacity in the to soil water holding capacity in the upper 25-30 cm. upper 25-30 cm.
Instrumentation Instrumentation
12 EC 3-D sonic anemometer 12 EC 3-D sonic anemometer (CSAT3)(CSAT3)
10 Open path CO10 Open path CO22/H/H22O IRGA (LI7500)O IRGA (LI7500)
2 Open Path H2 Open Path H22O (KH20)O (KH20)
Data CollectionData Collection– 20 Hz, 20 day times series20 Hz, 20 day times series– 30 Minute data, remainder of season30 Minute data, remainder of season
Ancillary InstrumentationAncillary Instrumentation
Net radiation (7-Kipp & Zonen, 7-REBS)Net radiation (7-Kipp & Zonen, 7-REBS)
Soil heat flux plates with soil T (REBS)Soil heat flux plates with soil T (REBS)
Vitel Vitel θθvv sensors sensors
Temperature and humidity (Vaisala)Temperature and humidity (Vaisala)
Radiometric temperatures (soil & canopy + Radiometric temperatures (soil & canopy + soil, Apogee)soil, Apogee)
Cross-Comparison LocationCross-Comparison Location
Exploratory Equivalence Exploratory Equivalence AnalysisAnalysis
(are the EC’s equivalent)(are the EC’s equivalent)
VariableVariable June 06June 06 Sept. 17Sept. 17 CVCV
COCO22 YesYes YesYes ~ <09%~ <09%
HH YesYes YesYes ~ <11%~ <11%
LELE YesYes YesYes ~ <10%~ <10%
July 04 02 Rainfall (mm)
Variation in PrecipitationVariation in Precipitation
Total Rainfall (6/1/02-8/19/02) (cm)
Variation in PrecipitationVariation in Precipitation
y = 0.8412x - 0.8565R2 = 0.85
10
15
20
25
30
35
40
10 15 20 25 30 35 40
Rn-G (MJ/m^2)
H+
LE
(M
J/m
^2
)
Energy Balance ClosureEnergy Balance Closure
Variation in Net RadiationVariation in Net RadiationDOY 179 Corn Positive Rn
-100
0
100
200
300
400
500
600
700
800
30 330 630 930 1230 1530 1830 2130
Hour
Rn (W
m-2
)
6 151 152 24 33 Avg
DOY 179 Corn Pos Rn Difference from Avg
-100
0
100
200
300
400
500
600
700
30 330 630 930 1230 1530 1830 2130
Hour
Rn
(W m
-2)
6 151 152 24 33 Avg
Little difference among net radiation across the sites
Seasonal Variation in Rn - Seasonal Variation in Rn - CornCorn
STD Pos Rn Corn
0
20
40
60
80
100
120
140
160
180
200
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
DOY
(W m
-2)
Seasonal Variation in Rn - Seasonal Variation in Rn - SoybeanSoybean
STD Pos Rn Soybean
0
20
40
60
80
100
120
140
160
180
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
DOY
(W m
-2)
Seasonal Variation in G - Seasonal Variation in G - CornCorn
STD SHF Corn
0
10
20
30
40
50
60
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
DOY
(W m
-2)
Seasonal Variation in G- Seasonal Variation in G- SoybeanSoybean
STD SHF Soybean
0
10
20
30
40
50
60
70
80
90
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
DOY
(W m
-2)
Variation in LE and COVariation in LE and CO22 Soybeans July 16, 2002
-2
-1.5
-1
-0.5
0
0.5
1
1.5
30 500 930 1400 1830 2300
CST (hr-min)
CO
2 m
g m
-2 s
-1
3
14
161
162
5b
Corn July 16, 2002
-4
-3
-2
-1
0
1
2
30 500 930 1400 1830 2300
CST (hr-min)
CO
2 m
g m
-2 s
-1
6
151
152
24
25
33
5a
Soybeans July 16, 2002
-0.05
0
0.050.1
0.15
0.2
0.25
0.30.35
0.4
0.45
30 500 930 1400 1830 2300
CST (hr-min)
H2O
mm
30m
in-1
3
14
161
162
5d
Corn July 16, 2002
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
30 500 930 1400 1830 2300
CST (hr-min)
H2O
mm
30m
in-1
6
151
152
24
25
33
5c
Variation in LE - SoybeanVariation in LE - Soybean
DOY 189 Soybean LE
-200
-100
0
100
200
300
400
500
600
700
30 330 630 930 1230 1530 1830 2130
Hour
LE (W
m-2
)
3 13 14 161 162 23 Avg
DOY 189 Soybean LE Difference from Avg
-400
-300
-200
-100
0
100
200
300
400
500
600
30 330 630 930 1230 1530 1830 2130
HourLE
(W m
-2)
3 13 14 161 162 23 Avg
Variation in Energy Balance Variation in Energy Balance ComponentsComponents
Blue- CornRed- Soybean
ObservationsObservations
Variation in energy balance Variation in energy balance components and COcomponents and CO22 among sites was among sites was larger than the comparison larger than the comparison differencesdifferences
Differences among sites were caused Differences among sites were caused the crop growth due to soil types and the crop growth due to soil types and soil water availabilitysoil water availability
Variation remained consistent Variation remained consistent throughout the study periodthroughout the study period
ImplicationsImplications
Multiple sites provide measure of the Multiple sites provide measure of the differences across soils within a differences across soils within a watershed settingswatershed settings
Careful selection of sites would be Careful selection of sites would be necessary to obtain data typical of necessary to obtain data typical of regional scale estimatesregional scale estimates
