Yield Monitors and Maps

BAE 4213April 12, 2007Randy TaylorBiosystems and Ag Engineering

What Are the Tasks? Measure grain flow

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

Flow Sensors

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

widthlength

mass

area

massYield

Width When do errors occur?

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?

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

Mass Flow Measurement Errors

Combine Dynamics Calibration

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

Mass Flow Sensors

Lag/Resonance Time

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

Transitional Mass Flow

What Causes Error?

R2 = 0.53

R2 = 0.86

R2 = 0.61

R2 = 0.78

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Average Mass Flow, lbs/s

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Ranking Plots

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Ideal

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

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

Using YM Data

1. Diagnosing Crop Production2. Estimating Nutrient Removal3. On-Farm Research4. Establishing Yield Potential (Goals)

1. 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

Problem Diagnoses

Wire worm infestation

Crop drowned

Presenting Yield Maps

5 – 6 ranges or groups maximum Based on

Natural Break Even Intervals Predefined Crop Standard Deviation Percent of Average

Color Scheme

Dryland Wheat Even Intervals

1996 1997

Dryland Wheat Predefined Crop

1996 1997

Dryland Wheat Percent of Average

1996 1997

Normalized Yield (96-97)

Data Aggregation

Point data Contouring

Some type of interpolation Likely have minimal or confusing choices

Grid Interpolated Averaged Summed

Points versus Interpolation

How many of the dark blue points are zero yield?

Header Status

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

Irrigated Corn/Beans Normalized Yield

1996 Beans/Corn 1997 Corn

Beans Corn

Average of Two Years

Interpreting Patterns

Straight lines are manmade Parallel with travel At an angle with travel patterns

Irregular patterns are generally naturally occurring Lines Areas/patches

Sand Pivot (1996-97 Crops)

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

Yield Variability

That which can be changed Fertility

That which must be managed Soil physical properties

3. 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?

YieldYield

TopsoilTopsoil

PopulationPopulation

Layering Maps

1998 Corn - Osage County

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Topsoil, inches

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4. 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?

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

‘Whisker Plots’ of YM Data

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Points are the mean relative difference for each cell

Bars are the standard deviation of yield through time.

Classification Maps

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

Conclusions

Yield monitor data can be used for anything that yield data are used for1. Diagnosing Crop Production2. Estimating Nutrient Removal3. On-Farm Research4. Establishing Yield Potential (Goals)