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Use of Multispectral Imagery for Variable Rate “Application-zone” Identification
in Cotton Production
Tim Sharp
Beltwide Cotton Conference
January 6-10, 2003
1. Introduction
Researchers have been trying to identify the correct management zones based mainly on the variability of the crop yield.
Airborne multispectral imaging of cotton can provide important spatial information
Spatial variations in crop vigor can be observed in green, red and near infrared wavebands
Multispectral images can be used to monitor the spatial and temporal changes in the growth of crops
Objective
The purpose of this study was to investigate the use of multispectral imagery
• As a tool to map cotton vigor zones
• Test the hypothesis that imagery from one year would map the zones in subsequent years (Zones are stable in time and space)
• Could these maps be a tool for variable rate application prescriptions in the following year
2. Material & Methods
• Positioning System– GPS NAVMAN / IPAQ
• Softwares– COTMAN– Farm Site Mate– ERDAS Image– SSToolbox– SAS
• Imagery Acquisition– Duncan’s camera (Green, Red, Near Infrared bands)– 0.5 to 1.5 meter resolution images were utilized
Field Data Collected
• Standard Data by productivity zone
– Stand
– Height
– Total Nodes
– Total Bolls
• Yield Map Data
• Total Final Plant Maps
3. Results and Discussion
IMAGE x NDVI - Barn
- Moose Lodge- Traveler Rest
3. Results and Discussion
Barn 9 - 2001
Low Medium
High
Low Medium
High
NDVI x NDVI – Barn
R2 = 0.5261
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.0 0.1 0.2 0.3 0.4 0.5
NDVI 2001
ND
VI 2
00
2
NDVI 2002
NDVI 2001
3. Results and Discussion
Moose Lodge 2 - 2002
Low
Medium
HighLow
Medium
High
NDVI x NDVI – Moose Lodge
R2 = 0.6176
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.0 0.1 0.2 0.3 0.4 0.5
NDVI 2001
ND
VI 2
00
2
NDVI 2002
NDVI 2001
3. Results and Discussion
Traveler’s Rest 1 - 2002
Low
Medium
High
Low
Medium
High
NDVI x NDVI – Traveler’s Rest
R2 = 0.69470.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
0.0 0.1 0.2 0.3 0.4 0.5 0.6
NDVI 2001
ND
VI 2
00
2
NDVI 2001
NDVI 2002
3. Results and Discussion
Wildy 4 – 2002 (Irrigated)
Low
MediumHigh
Low
MediumHigh
NDVI x Yield – Wildy (Irrigated)
R2 = 0.7827
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
NDVI 2001
ND
VI 2
00
2
Yield 1998
NDVI 2002
3. Results and Discussion
Year 2001 vs Year 2002- Stand- Height
- Total Nodes- Total Bolls
3. Results and Discussion
MOOSE LODGE
BARN
TRAVELERS REST
A A A0.0
0.6
1.2
1.8
2.4
3.0
L M H
NDVI Zones
Sta
nd (
plan
ts/fo
ot)
AAA0.0
0.8
1.6
2.4
3.2
L M H
NDVI Zones
Sta
nd (
plan
ts/fo
ot)
A A A0.0
0.8
1.6
2.4
3.2
L M H
NDVI Zones
Sta
nd (
plan
ts/fo
ot)
STAND 2001 vs 2002
Tukey's Studentized Test with alpha at 5% - Means with the same letter are not significantly different.
3. Results and DiscussionBARN
C B A0.0
10.0
20.0
30.0
40.0
50.0
L M H
NDVI Zones
Hei
ght (
inch
es)
MOOSE LODGE TRAVELERS REST
C B A0.0
10.0
20.0
30.0
40.0
50.0
L M H
NDVI Zones
Hei
ght (
inch
es)
ABC0.0
10.0
20.0
30.0
40.0
50.0
L M H
NDVI Zones
Hei
ght (
inch
es)
HEIGHT 2001 vs 2002
Tukey's Studentized Test with alpha at 5% - Means with the same letter are not significantly different.
3. Results and DiscussionBARN
ABC0.0
5.0
10.0
15.0
20.0
L M H
NDVI Zones
Tota
l Nod
es
MOOSE LODGE TRAVELERS REST
B A A0.0
5.0
10.0
15.0
20.0
L M H
NDVI Zones
Tota
l Nod
es
ABC0.0
5.0
10.0
15.0
20.0
L M H
NDVI Zones
Tota
l Nod
es
TOTAL NODES2001 vs 2002
Tukey's Studentized Test with alpha at 5% - Means with the same letter are not significantly different.
3. Results and DiscussionBARN
B A A0.0
2.0
4.0
6.0
8.0
L M H
NDVI Zones
Tota
l Bol
ls (
bolls
/pla
nt)
MOOSE LODGE TRAVELERS REST
B B A0.0
4.0
8.0
12.0
L M H
NDVI Zones
Tota
l Bol
ls (
bolls
/pla
nt)
AAB0.0
2.0
4.0
6.0
8.0
L M H
NDVI Zones
Tota
l Bol
ls (
bolls
/pla
nt)
TOTAL BOLLS2001 vs 2002
Tukey's Studentized Test with alpha at 5% - Means with the same letter are not significantly different.
Summary and Conclusions
Summary and Conclusions
• Some researchers have reported in other areas of the country that zones change position.– May be due to wet soil conditions– May not have enough total variability in the
field to fully express zone identity• In our study the medium zones may or may not be
significantly different from either the low or high zone from one year to the next
In West Tennessee
• Zones did not move from year to year.– With over 100 fields studied across three years– Final Plant Map data were collected from each
of the five NDVI classed zones in each field– We never found that the low classed NDVI
zone or the High Classed NDVI zone were incorrectly identified
– Confirmation plots agreed completely with research site data
Implications
• NDVI classed maps obtained after 550 DD60 NAWF 5 but prior to defoliation– Will accurately map the productivity zones for
the following years– Will allow for the opportunity to plan Variable
Rate Applications based on those classed maps in subsequent years
– Correctly maps and predicts the cotton vigor to be expressed in those areas
Acknowledgements
• National Cotton Council
• National Science Foundation
