1. Yield Monitors and Maps
BAE 4213
April 12, 2007
Randy Taylor
Biosystems and Ag Engineering

2. What Are the Tasks? Measure grain flow Measure ground speed
Mass or Volume Flow Sensor
Measure ground speed
Existing ground speed sensor or position sensor signal
Program harvest width
Programmed as a constant value or changed on-the-go
Combine position
GPS Position Sensor

3. Flow Sensors

4. Yield Monitor Errors How do we calculate yield
Yield errors must be related to one of these 3 measurements: mass, length, width
For a yield monitor
Mass is determined from the flow sensor
Width is a programmed constant
Length is determined from speed

5. Width When do errors occur? How do we fix it?
header not full (i.e. harvest width does not match header width)
How do we fix it?
Adjust on the go => bad idea
How much error are we really talking about?
U of Missouri research found it was 8-12% in drilled beans if they assumed constant full header
How much do you have to reduce harvest width to get area (field) to be accurate?

6. Distance Errors
UNL Research harvesting up & down slope found no significant difference in mass accumulation.
However they found a 42’ difference going uphill verses down on a 6% slope
Though GPS was the intended speed signal, differences in end points was not observed in a GIS
The greater distance measurements going uphill cause a reduction in calculated yield

7. Mass Flow Measurement Errors
Combine Dynamics
Calibration

8. Combine Dynamics Crop is cut or removed from plant
Conveyed to feeder house in the header
Conveyed to threshing unit (cylinder or rotor)
~80% of separation should occur during threshing
~20% of grain goes on to separation (rotor or straw walkers)
Grain that falls on the cleaning shoe should pass through near the front of the shoe
Grain that goes through the returns
All of these affect the grain flow relative to its former location in the field

9. Mass Flow Sensors

10. Lag/Resonance Time

11. Sensor Calibration Response to mass flow is non linear
Diaphragm vs Triangular
Can get a very good fit with linear
Operating at points away from one calibration can cause errors
Where do we see these?
Start and stop grain flow

12. Transitional Mass Flow

13. What Causes Error?

14. Ranking Plots

15. Using YM for OFR
50% of the error between weigh wagon and yield monitor weights was due to mass flow
Correlation between yield monitor and weigh wagon weights was 0.97
Regression results lead to the same conclusions regarding the treatments
Challenging to rank treatments with YM data

16. How do we assess performance?
Compare Weight measured by the yield monitor to that measured with a certified scale.
Same procedure as calibration
How small of scale should we use?
We should be able to achieve <5% error at field scale

17. What Can a Yield Map Tell Us?
Soil fertility, type, etc.
Disease or insect pressure
Variety differences
Poorly drained areas
Compacted areas
Does not point out the yield limiting variable, it only indicates the response to it

18. Using YM Data Diagnosing Crop Production Estimating Nutrient Removal
On-Farm Research
Establishing Yield Potential (Goals)

19. Diagnosing Crop Production
Probably the most widespread use for yield maps today
Print maps to keep records on
Select appropriate ranges
Number of ranges
Spread (don’t create or exaggerate variability)
Color scheme

20. Problem Diagnoses
Wire worm infestation
Crop drowned

21. Presenting Yield Maps 5 – 6 ranges or groups maximum Based on
Natural Break
Even Intervals
Predefined Crop
Standard Deviation
Percent of Average
Color Scheme

22. Dryland Wheat Even Intervals
1996
1997

23. Dryland Wheat Predefined Crop
1996
1997

24. Dryland Wheat Percent of Average
1996
1997

25. Normalized Yield (96-97)

26. Data Aggregation Point data Contouring Grid Some type of interpolation
Likely have minimal or confusing choices
Grid
Interpolated
Averaged
Summed

27. Points versus Interpolation
How many of the dark blue points are zero yield?

28. Header Status
Raised the mean yield about 5 bu/ac, but did it really make a difference?

29. Irrigated Corn/Beans Normalized Yield
1996 Beans/Corn
1997 Corn
Beans
Corn

30. Average of Two Years

31. Interpreting Patterns
Straight lines are manmade
Parallel with travel
At an angle with travel patterns
Irregular patterns are generally naturally occurring
Lines
Areas/patches

32. Sand Pivot ( Crops)

33. Yield Variability Many causes of yield variability
Yield monitors and maps don’t determine the cause
Yield maps display the location and magnitude (area and degree)
This information should lead to better decisions

34. Yield Variability That which can be changed That which must be managed
Fertility
That which must be managed
Soil physical properties

35. On-Farm Research
Has the potential to expand knowledge about individual farms
Comparison of varieties, tillage practices, fertility rates, etc.
Not as easy as it may seem
What do you want to know?
Why do you want to know it?

36. Layering Maps
Yield
Topsoil
Population

37. 1998 Corn - Osage County

38. Prescribing Spatial Inputs
Some input recommendation models require the use of a crop yield goal
Development of a nutrient recommendation map may require the use of a yield goal map
How can you generate variable yield goals?

39. Yield Stability Analysis
Data were obtained with various yield monitors
Converted to point yield and unrealistic values were removed
Data were block averaged to 180 foot cells

40. ‘Whisker Plots’ of YM Data
Points are the mean relative difference for each cell
Bars are the standard deviation of yield through time.

41. Classification Maps

42. Mean Relative Difference
Standard statistical analysis offers minimal insight into spatial data
Low yielding cells tend to be more variable
There is a better opportunity to classify consistently low yielding areas
Because like classed cells were spatially contiguous, this method showed more promise than typical methods

43. Conclusions
Yield monitor data can be used for anything that yield data are used for
Diagnosing Crop Production
Estimating Nutrient Removal
On-Farm Research
Establishing Yield Potential (Goals)