Sensor-based nitrogen management techniques can help reduce nitrogen usage and costs for cotton farmers. The document outlines a study in Coastal Plain soils that found sensor-based methods reduced nitrogen application by 15-100 lbs/acre for cotton compared to farmer practices, saving $9-60/acre. Soil electrical conductivity mapping and plant nitrogen rich strips were used to identify management zones. Mid-season plant NDVI readings from sensors were calculated in an algorithm to determine variable-rate nitrogen applications, accounting for soil amendments and previous crops. Results showed no yield differences between farmer practices and sensor methods, indicating potential for sensor technology to cut nitrogen costs for cotton growers.

1. Sensor-based Nitrogen
Management for Cotton in
Coastal Plain Soils
Sensor-based Nitrogen
Management for Cotton in
Coastal Plain Soils
Phillip Williams, Ahmad Khalilian,
Michael Marshall, Jose Payero,
Ali Mirzakhani
71st SWCS International Annual Conference
Louisville, KY, July 24-27, 2016

2. ACKNOWLEDGMENTS
This Demonstration project is supported by:
USDA/NRCS CIG
Award No. 69-3A75-14-268
Clemson Public Service Activities
This Demonstration project is supported by:
USDA/NRCS CIG
Award No. 69-3A75-14-268
Clemson Public Service Activities

3. ClayClay
SandSand
Sandy LoamSandy Loam

4. Field variations result in the development
of plants with a tremendous amount of
growth variability, which have a major
impact on fertilizer management strategies.

5. Cotton Yield
CottonLint(lbs/acre)
Soil EC (mS/m)
R
2
= 0.9202
0
300
600
900
1200
0 2 4 6 8
Soil EC, at planting

6. N Rate (lbs/A)
LowEC: Medium High
0
500
1000
1500
2000
2500
0 20 40 60 80 100 120 140
Effects of soil EC and N rate on seed
cotton yields (lbs/acre)SeedCottonYield

7.  Several researchers have developed
algorithms for sensor-based N
applications for corn, cotton & wheat.
 However, due to higher precipitation,
significant variation in soil texture, low
soil organic matter content, and low
nutrient holding capacity of soils in
Coastal Plain regions, N-application
algorithms, developed at other regions,
either under- or over-estimated
nitrogen rates for crop production.

8. EC Zones
SeedCottonYield
Effects of Nitrogen Management
Systems on Cotton Yield
Clemson
Farmer
OSU
Low Medium High
0
500
1000
1500
2000
2500
3000

9. Clemson Yield Prediction Equations
INSEY
Seed Cotton Yield
y = 320.31e112.2x
R² = 0.761
y = 502.82e116.07x
R² = 0.8837
0
500
1000
1500
2000
2500
3000
3500
0 0.005 0.01 0.015 0.02 0.025
Irrigated
Dry Land

10. Algorithm Comparison
Clemson Algorithm OSU Algorithm
YP0= 235.96 e 2216.2 * INSEY
INSEY= NDVI/Cumulative
GDD
RI = 1.8579 * RINDVI – 0.932
%N= 0.09
NUE = 0.50
(YP0 * RI –YP0) * %N
N Rate =
NUE
 YP0= 413.46 e104.98 * INSEY
 INSEY= NDVI/# Days After
emergence
 RI = High NDVI/Field Avg. NDVI
 %N= 0.04
 NUE= 0.50

11. EC Zones
SeedCottonYield(lbs./acre)
Sensor:47 lb./A Conv.:90 lb./A ($48% less)
Low Medium High
0
1000
2000
3000

12.  On average, growers in the US apply
about 90 lb./acre N for cotton, for a
total of 1.7 million tons.
 Sensor-based N application has the
potential to reduce nitrogen rates by
half. Even a 20% reduction in
nitrogen rate could save our cotton
growers over $100 million annually.

13. Objective
To demonstrate the benefits of
sensor-based nitrogen
management strategies to growers,
utilizing plant NDVI, Clemson
algorithms for Irrigated and dry land
cotton, soil amendments, and soil
electrical conductivity (EC) data
(management zones).

14. Overall Objective
To assist cotton, corn, and wheat
farmers in the Southeastern
Coastal Plain region, to adopt
innovative and proven conservation
technologies for achieving 4R (right
source, rate, time, and place)
nutrient management.

15. Demonstration Sites (2015-16)
Al Cribb Farm
Walker Nix Farm
Jeff Lucas Farm
Williams Farm
JB Farms
Bates Farm
Edisto REC (3 sites)
Pee Dee REC (2 sites)

16. Identifying management zones
Establishing nitrogen rich strips
Measuring NDVI utilizing sensors
Calculating nitrogen requirements
Methods for Managing Nitrogen

17. Soil Electrical
Conductivity (EC) meter
EC Map, Cribb Farm
Identifying management zones

18. 4 rows by 50 feet; More nitrogen than the
plants can use is applied (150 lbs/A for cotton).
Establishing nitrogen rich strips

19. Measuring NDVI utilizing sensors
NDVI = (NIR - Red) / (NIR + Red)

20. Handheld Data Collection
• Handheld units
–Mobile
–Cost effective
• Only does small area
but gives average

21. Whole Field NDVI Mapping
• Sensors mounted on sprayer booms,
fertilizer applicators, or any mobile field
equipment.
• Provides a whole field map that can be used
in fertilizer applicators or can apply fertilizer
“on-the-go”.

22. Aerial Mapping
• Unmanned Aerial Vehicle (UAV) can be
used to fly over fields and collect data that
can then be made into a prescription map.

23. Calculating nitrogen requirements
• Excel file can be used to calculate N rates.
• NDVI data from UAV, handheld, or field
equipment can be used as input.

24. Mobile Application and Website
The application is designed for smartphones, tablets
and computers.

25. Planting Date
NDVI: N Rich Strip
NDVI: Field
Max Yield History
Irrigated or
Dryland
N-rates for each zone

26. Variable-rate Nitrogen Applicator
Rawson Hydraulic Controller

27. 2015 Test Results
Farm
Previous
Crop
N At
Planting
(lbs./acre)
Sensor‐based N
Zone 1 Zone 2
(lbs./acre)
Grower N
rate
(lbs./acre
)
N Saved
(lbs.
/acre)
Savings
($/acre)
Walker Peanuts 0 40 20 90 50 ‐70 30 ‐ 42
Al Cribb Cotton 45 0 0 90 45 27
Jeff
Lucas
Clover
Chicken
litter
0 0 90‐100 90‐100 54‐60
Pee Dee Cotton 0 40‐100 Ave. 60 75 15 9
Statistically there were no differences in
cotton yields between farmers’ practice and
sensor-based method at all locations

28. There is a potential to use mid-
season plant NDVI data for variable-
rate application of N fertilizer in
cotton production, in a user friendly
manner that growers and extension
can utilize.
Summary

29. Soil EC management zones should be
used for calculating nitrogen
application rates in the Southeastern
Coastal Plain region. This in addition to
sensor technology can work in
conjunction to give growers more
information to make better
management decisions.
Summary

30. Soil amendments (such as poultry
litter) and/or previous crops (such as a
legume like peanuts or soybeans) had
a significant effect on required
nitrogen rates determined by a sensor.
Summary

31.  Sensor-based N management
techniques, reduced nitrogen usage
by 15 to 100 lbs./acre in cotton,
compared to growers‘ application
rates. This resulted in $9 to $60
savings/acre.
Summary

32. Questions?Questions?