Yield Monitors & Field Mapping
What is a Grain Yield Monitor
• A grain yield monitor is simply an electronic
tool that collects data on crop performance
for a given year. The monitor measures and
records such information as grain flow, grain
moisture, area covered, and global location.
Yield Monitors
Yield Monitors
Yield Monitor produced by Insight the most popular brand of yield
monitors in the world.
Parts of a grain yield monitor
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Data storage device
User interface (Keyboard, Display screen)
A Task Computer
Sensors ( Moisture,Volume,Speed,Location)
Grain Flow Sensors
• The most essential component of any yield
monitoring system is the sensor used to
measure the mass or volume of clean grain
moving through the separator of a combine.
While the nature of mass-flow or volumetricflow sensing may vary by manufacturer, these
devices are almost always located at or near
the top of the clean grain elevator, as shown
in Figure 3.
Mass-Flow Sensing
• The most common approach is mass-flow sensing, which is accomplished
by assessing the impact force of grain hitting a plate. The paddles of the
clean grain elevator accelerate grain as the chain makes a 180° turn at the
top of the elevator. The centrifugal acceleration generated as the paddles
make this turn causes the grain to separate from the paddles. Grain then
contacts the elevator enclosure and falls toward the base of the bin
loading auger. It is at this location, where grain impacts the elevator
housing, that impact-type sensors are positioned.
• An impact sensor measures the mass flow rate of grain through a combine
by sensing the force of grain as it impacts a plate or beam, using either a
strain gage or a linear potentiometer to measure deflection of the beams
or various members holding the plate. Because the impact sensor is the
most prevalent type of grain flow sensor in the United States, it is the
primary focus of this publication. Three other sensors—radiation-based,
photoelectric, and paddle wheels—are also explained because they have
been incorporated into a number of commercially viable products.
Mass Flow Sensor
Ground Speed Sensor
• Ground speed can be easily measured using the existing
magnetic pick-up provided by the combine manufacturer. A
square wave is generated as ferrous gear teeth within the
transmission. One of the problems with this approach is
measurement error due to wheel slippage. Radar provides an
alternative method for measuring ground speed and is
preferable when compared to the magnetic sensor pick-up. It
is not subject to wheel slip errors, which can be an important
factor when combines are operated in unfavorable conditions
such as on wet soil.ansmission pass the magnetic pick-up
Moisture Sensor
• Today, most moisture sensors are mounted on
the side of the clean grain elevator. This location
is better than mounting the sensor on the tankloading auger because the sensors encounter less
grain flow, reducing the buildup of debris on the
sensor plates. This buildup introduces bias into
the moisture measurements. The moisture
sensor is essentially a conductive shell or metal
plates with an electrically isolated internal metal
fin.
DGPS Sensor
• The Digital Global Positioning System is used
to get a real time location of the combine in
the field.
• Initially developed for national security
interests, a portion of the system is available
to civilians. When yield data is combined with
info from a dgps receiver, a yield map can then
be produced.
Yield Map
Yield Map Variance Interpretive Guide
Pattern Description
Straight Line Patterns
Irregular Patterns
Direction of Application
Against Direction of
Application
•change in planting
date
•change in
hybrid/variety
•change in chemical
application
•selected rescue
treatment
•chemical skips and
misapplications
•equipment errors
•poor straw/chaff
distribution
•compaction
•change in soil type
•drainage patterns
•tile patterns
•topography changes •weed infestations
•historically different
•herbicide drift
•soil fertility changes
fields
•border shading
•previous crop
•old traffic patterns
effects
activity
•manure applications
•insect infestation
•disease infestations
•pipelines/phone
from bordering lands •herbicide carryover
lines underground
•improper manure
•historic occurrences
•previous compaction
application
•insect infestations
•old laneways/fence
•waterways
•changes in o.m.
lines
•animal damage
•wet areas
Irregular Line
Irregular Area/Patch
The Benefits of Yield Monitors
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In-Field, Real-Time Benefits During Harvest
Collect on-farm testing results with little or no disruption of the harvest operation
Note and avoid catastrophic combine grain spills using the instantaneous yield
monitor readout
Co-mingle grain accurately with multiple farming partners but insufficient on-farm
grain storage
Facilitate on-the-go grain moisture decisions, e.g. "Should grain go to the drier or
to town?"
Know where to move grain earlier by avoiding the wait for scale readings
Optimize combine throughput but minimize post-header grain losses by keeping
bu/hour reading within a desired productivity range
Use real-time yield information to capture early-season contracts or marketing
premiums when
The Benefits of Yield Monitors
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On-Farm Benefits
Create detailed Field and Load yield summaries
Evaluate the cost of poor weed control
Evaluate the effects of poor drainage and estimate the pay-back period for tiling
Achieve greater convenience in evaluating management practices such as plant
populations, row spacing, tillage, hybrid and variety selection, date of planting,
plant nutrient applications, pesticide choices, etc.
Document the cost of management errors such as nutrient application skips
Evaluate the effects of variable soil nutrient and pH levels on crop yield
Quantify yield losses within a field due to field margin effects, landscape position,
soil differences or crop pest infestations
Evaluate hybrid consistency within a field
Document planting and other field activities in time and space. Develop a
historical spatial data base
Locate best areas for yield contest plots
Map cost of production and farm around perennially unprofitable areas
The Benefits of Yield Monitors
• Off-Farm Benefits
• Offer custom yield mapping services to other
farmers
• Custom harvesters can offer yield mapping
services or better document acreage and
productivity
• Document the spatial history of special end-use
crops to add value with identity-preserved
marketing
• Increase farm/field value upon sale with proven
yield history and related spatial data base
Considerations when purchasing
• When you make this first move into precision
agriculture, your choices are limited by what is
available and the level at which you intend to
enter the technology. Cost for yield monitoring
systems range from $2,000 for a user-installed
yield monitor alone to more than $8,000 for a
complete turn-key system that includes a yield
monitor, DGPS receiver, mapping software
package and installation with the purchase or
lease of a new combine
Considerations When Purchasing
Before purchasing ask yourself these questions
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Is a yield monitor available for your make and model of combine?
Are you considering the purchase of a combine from a manufacturer that provides
yield monitoring as an option or add-on?
Do you trade combines frequently?
Will more than one combine be operated in the same field?
Will yield monitoring capabilities be obtained from a custom harvester?
Do you want to generate yield maps or simply obtain field average yield data at
harvest?
Who will download yield data and generate yield maps?
Do you own a personal computer with color printer and PC card interface?
Which map generation package will you use?
How will you archive yield data for future use?
Will you purchase a DGPS receiver with the yield monitor?
How will differential correction signals be obtained for the DGPS receiver?
Will you purchase an integrated package, or will you develop yield monitoring
capabilities over several years?
Can components of the yield monitor be used in other applications (e.g. variable-rate
seeding)
How to operate a combine with a yield
monitor
• The final appearance of a yield map depends on how
the combine is operated. Frequent stopping or sudden
changes in speed can cause erratic yield data due to
the delay and smoothing phenomena associated with
the combine separating system.
• The combine must be operated on a uniform swath
width to ensure accurate yield data. The width of the
header must be manually entered into the monitor to
accurately calculate yield. Yield will be underestimated
if fewer rows are harvested. Many yield monitors allow
the operator to change the number of rows or the
percent of width harvested to correct yield for point
rows or field edges.
The Benefits of Yield Monitoring and
field mapping
• In summary a yield monitor is just a tool used
take measurements of real time grain yield.
When combined with geographical references
it can create a useful image of field and grain
conditions. When the information is properly
interpreted it allows the farmer to make
informed management decisions whether he
is taking grain to the dryer, or making changes
to his variable rate nutrient management
program.