By Sharon Omahen
University of Georgia
Most farmers know that different areas of their fields produce
better crops than others. Now yield maps can tell them exactly
where these areas are and how to improve or avoid them.
“One farmer called it his entrance and exit exam,” said Calvin
Perry, an agricultural engineer with the University of Georgia
College of Agricultural and Environmental Sciences.
“When you show farmers yield maps,” Perry said, “most of them can
tell you why the yield differs across the field.”
Software and yield monitors create map
To make a yield map, specialized software converts raw data
collected by a yield monitor into an easy-to-read image of the
field. The yield monitor consists of a yield-sensing device, a
Global Positioning System receiver and a computer console
attached to a harvester.
“The console reads the yield sensor every second and gets a value
for yield,” Perry said. It matches the yield data with the
location with GPS, then stores and uses both to create the yield
map.
“A yield map has colored pixels that represent where the yield
data point was collected and how much yield occurred at that
spot,” he said.
Yield monitors are available for cotton, root crops and grain
crops like corn, wheat and soybeans. Cotton farmers have just
begun using them, since cotton yield monitors are fairly new,
Perry said.
As many as 30 percent of grain farmers use them. “Grain yield
monitors have been around 15 years,” Perry said.
A prototype peanut yield monitoring system was developed by the
UGA precision agriculture team at the National Environmentally
Sound Production Agriculture Laboratory in Tifton, Ga.
“The system was licensed by a company to begin marketing it to
farmers,” Perry said. “But the company encountered financial
difficulties and will not be able to produce the yield monitor.”
Effective, but pricey
Yield monitoring isn’t the cheapest tool farmers have. “A yield
monitor for a typical grain combine would cost about $4,500,”
Perry said. “A four-row cotton picker yield monitor would cost
around $6,500 and a six-row system about $8,000.” These prices
don’t include the GPS receiver, another $800 or so.
“Large farmers can afford to invest in technology like this,” he
said. “It’s harder for smaller farmers to do the same. … It’s
hard for them to justify spending money for gear that produces a
map.”
But the maps can help farmers manage future inputs.
“In one case, a yield map showed a farmer he actually had a
higher yield where he didn’t spray herbicides,” Perry said. “The
yield map definitely made him pay more attention to his herbicide
spraying.”
Yield maps have pointed out equipment errors, too, like
malfunctioning or overlapping sprinklers.
“A lot of things pop out in yield maps that would otherwise go
unnoted,” Perry said. “It really hits home to a farmer when you
show them an area where they’re losing money. It makes the farmer
take notice and make changes.”
Besides their main uses, yield maps can be useful in placing
value on land. “They come in handy for land value negotiations,
estate and will issues and assessing management decisions,” Perry
said.
New tool, not replacement tool
Perry said yield maps should be used as another farming tool, not
a replacement tool.
“Yield maps are by no means meant to replace scouting (for
insects and diseases) and sampling,” he said. “They’re just one
tool of many that farmers should be using.”
As with other tools, yield maps have to be used right.
“You can’t just have one yield map and think you can use it for a
long time,” Perry said. “Yield maps will be different on the same
field in different seasons because the weather patterns are
different.”
As more farmers use yield maps, county Extension agents are
fielding more questions. Perry and other UGA, Auburn University
and U.S. Department of Agriculture researchers train agents to
answer them. The most recent training,
sponsored by the NASA
National Space Grant Program, was held at UGA’s Griffin campus
last month.
