Combine Yield Monitors
Current Yield Monitors
Mass-flow sensor
 Volumetric-flow sensor
 Conveyor belt load sensor
 Trailer load sensor
 Torque transducer

Basics of Yield Monitoring

Possible Crops to Monitor
– Wheat and other grains
– Cotton
– Potato and Sugar Beets
– Beans
– Rice
– Specialty Crops
 Grapes,
Tomatoes, Carrots, etc.
Impulse Yield Sensors
John Deere
Case
Ag Leader
Micro Trak
Impulse Flow Meter Force Vectors
Dynamincs of an Impulse Flow Meter
G mv
d mv

 F y G 
dt
v d m m dv


dt
dt
Assuming velocity is constant at t=t1
v dm
F y 
dt
Non-Impulse Yield Sensors
Nuclear Massey Ferguson - Europe
High Frequency Radio Waves
New Holland - Not
marketed
Capacitance Moisture Sensors
Micro Track
John Deere
Ag Leader
Case
Yield Mapping Trailer
(Sugar Beet Harvest)
Yield Mapping Trailer

Measures change in weight in the
trailer while allowing for
comparison at different times.

Can be used for any crop that is
loaded into a trailer continuously
while harvested.
Conveyor Yield Monitor
Corn Silage

The drive shaft of the base unit powering the
cutterhead, feedrolls, and front attachment, are
instrumented with strain gauge torque transducers.

Cutting power is linearly related to material feedrate.

Material flow can be expressed as:
– Fr(t)=Yi(t)Sp(t)W
Capacitance Moisture Sensors
Sources of Yield Map Error
Unknown swath width
 Time lag of grain through combine
 GPS error
 Multiple paths through combine
 Surging of grain through combine
 Grain losses
 Sensor Calibration

Sources of Impulse Yield
Sensor Error
Grain Moisture
 Grain Test Weight
 Grain Temperature
 Grain Cultivar
 Grain Species
 Contamination

– Dirt
– Plant oils, sap, etc.
Effect of Lag Time on
Combine Yield Measurements
Crop Yield Along Swath
Yield
Actual
Grain
Yield
t
P
Yield
t0
P
Yield Monitor
Measured
Grain Yield
t
Grain Flow Rate
V (t )  r (1 e
(
t  p t )
q
0
1
)  r (1 e
(
t  p t )
q
0
2
)
V(t) = output grain flowrate at sensor
r = magnitude of flow rate step input at header
P = transportation delay
P = 18.92 – 0.60 r for Gleaner N-6
q = time constant
q1 = 2s for combine into crop
q2 = 10 s out of crop
t0 = time of step input
From Searcy et al., 1989 Trans. ASAE 32:826 - 829
Comparison on Raw and Filtered
Combine Flowrate Data
Smoothing Effect of the Straw Walkers
Combine Yield Monitor and Satellite
Estimated Wheat Yield Maps
Yield Monitor 26.4 bu/ac
Satellite Estimate 28.7 bu/ac
GPS Error in Corn – Loss of Differential
Correction Signal
Oklahoma Panhandle, 1998
Two Combines in the Field with only
One Equipped with GPS
Oklahoma Panhandle, 1997
Corn Yield Surface with Krieging
Oklahoma Panhandle, 1997
Corn Yield Surface with Krieging
Oklahoma Panhandle, 1998
Wheat Yield Under a Center Pivot
Irrigation System
Oklahoma Panhandle, 1998
Wheat Yield Under a Center Pivot
Irrigation System
Oklahoma Panhandle, 1997
Wheat Yield Under a Center Pivot
Irrigation System
Oklahoma Panhandle, 1997
Wheat Yield Under a Center Pivot
Irrigation System
Oklahoma Panhandle, 1998
Data Misaligned Because of the Lag in
the Combine
Error Caused by the Lag in the Combine
Missing Data
English Wheat Field - Single Soil Type
Southwest Iowa Corn Field
Yield
Moisture
AgLeader Cotton Yield Monitor
Developed by John Wilkerson – University of Tennessee
Peanut Yield Monitor
University of Georgia
5 Class Krieg
Lime Streaking
Yield Map
NDVI Map
Lime Streaking not evident
Courtesy of Tim Sharp Jackson State C.C.
5 Class Krieg
Yield Surface
With Lime Streaking
NDVI surface
With lime streaking
Courtesy of Tim Sharp Jackson State C.C.
Fertilizer Streaking
5 Class Krieg
Spinner Applicator
Yield Surface
NDVI Surface
Courtesy of Tim Sharp Jackson State C.C.
Major Challenge

Correlate
NDVI
surface
data with
yield
surface
data
NDVI Vs Yield Curve 2001
R2 = 0.8731
0.6
0.5
0.4
0.3
0.2
0.1
0
0
200
400
600
800
1000
Courtesy of Tim Sharp Jackson State C.C.
1200
1400
Cotman Sample Points
Low
Medium
High
Courtesy of Tim Sharp Jackson State C.C.
NDVI 5 Class
Surface of Cotton
Red is Bad
Green is Good
Note Image of
Surrounding
Fields, they were
Top-dressed with
A spreader buggy
By the grower
Severe
Streaking
Courtesy of Tim Sharp Jackson State C.C.
5 Class NDVI with
Fertilizer streaking
Green, Red, NIR image
Composite
Courtesy of Tim Sharp Jackson State C.C.