Harvest Tech Alert

Getting Quality Yield Data Takes Time, Work

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Calibrating mass flow sensor, moisture sensor and measured area harvested are important steps to ensuring accurate yield data this fall. (DTN photo by Pamela Smith)

ROCKVILLE, Md. (DTN) -- Are you sure the data your yield monitor is recording are accurate?

Ron LeMay, CEO of the farm data analytics company FarmLink, learned a hard lesson on this seven years ago. "We started collecting yield data with state-of-the-art technology at the time," he recalled. "But as we examined it and started going through our quality assurance process, we realized we had a lot of suspect and bad data. We ended up throwing out 70% of the total data points we collected that year."

With yield monitor and GPS technology in every combine, collecting yield data is increasingly easy. But collecting good, accurate data worth basing major farm decisions on? That's much harder, says Ohio State University agricultural engineer John Fulton.

"The process of calibrating a yield monitor and making sure data are accurate throughout harvest can be a bit tedious from an operator standpoint," he said. For each point of data to be accurate, growers need to calibrate multiple sensors -- the mass flow sensor, grain moisture sensor, and measured area harvested. These calibrations should also be made when growers switch crops and encounter significant differences in grain moisture between fields, Fulton said.

Other important steps include checking for updates in your yield monitor, GPS and auto steer firmware, as well as checking the condition of your mass flow sensor plate.


When calibrating a mass flow sensor, farmers really need a multi-point calibration, Fulton said. That means making sure the sensor is accurate across a range of expected grain flows -- from the high flow in high-yielding spots of the field to the lower flow of thinner areas.

To mimic this effect, Fulton recommends calibrating at lower and higher combine speeds. "Drive from 2 to 5 miles per hour to adjust the flow through the combine," he said. "You want to harvest from 3,000 to 8,000 pounds and then compare the weight of that known load to what the yield monitor at that particular speed estimates. The calibration procedure will adjust accordingly."

It may be tempting to just clock in two grain flow rates above and below average and call it a day. But calibrating over the entire possible range of light to heavy flow rates is far more advisable, especially in years of varied crop quality and yield, Fulton said.

"Just for example, here in Ohio, we have a wide range of yield in corn and soybeans this year," he said. "You really want to make sure the mass flow sensor is accurately measuring at a low flow rate all the way up the continuum to a 200-plus, high-yielding scenario."

This should be done before you switch crops, but also when you move from low- to high-moisture fields within the same crop, Fulton added. "An incorrect moisture content will ultimately create an error in the yield estimate," he said.

Check those grain cart measurements, too, Fulton said. "A lot of guys use grain carts for calibrating monitors and you'll want to make sure the grain cart is accurate compared to certified scales."

The mass flow sensor plate at the top of the clean grain elevator can become worn, especially in older systems, and need to be replaced, Fulton added. "That's another pre-harvest check I would encourage," he said. "A lot of them are coated with a polymer, and you can see severe rounding of the edges or deterioration to some degree."


A number of components go into how the mass flow sensor measures the flow of grain. "It is influenced by grain properties, such as test weight and grain moisture, so if those are changing, it could influence the sensor's measurement," he said.

That means you should separately check and calibrate your moisture sensor, too. "Compare what the sensor estimates a crop's grain moisture to be against a known moisture, typically a certified grain moisture sensor, and adjust accordingly," he said. "That should be done every year for every crop." Since temperature plays into moisture estimates, it would be wise to check the temperature sensor's accuracy, which can be completed through the display, he added.

Fulton also recommends calibrating your system's estimate of the area harvested, which affects how yield data is recorded. "The main component is making sure the swath width of the head, or the number of rows is entered appropriately," he said. When growers make partial passes that don't use the full header width, they should make sure to input that correctly, he said.

The other side of the area harvested equation is the distance traveled. Growers with newer combines can simply use the GPS speed to make sure that is accurate, Fulton said. "But on older combines and monitors, sometimes the ground speed is provided by the transmission sensor or groundspeed sensor and they should check that the output of that is accurately measuring distance," he added.

GPS systems, yield monitors and auto steer systems often get firmware updates from year to year. Fulton recommends calling your dealer to check and installing any updates every year.

It's a lot of work to stomach with the furious pace of harvest underway or looming, Fulton conceded. But yield data is increasingly important in nearly every sector of agriculture. Precision ag services, on-farm research and most farm management decisions rely heavily on it.

"It's our ultimate measure of production," LeMay pointed out.

FarmLink now has its technicians run their equipment through a 300-point checklist before harvest. Thirty of those points are just related to accurate data collection, LeMay said. "Farmers operate in a hostile environment at harvest," he noted. "It's hot, dusty, rushed. It's not your typical data collection environment. You have to compensate for that. If you don't, then you'll produce big data but you won't know what's good or what's bad."

For more information, see Fulton's article on this topic from Ohio State University here: http://bit.ly/….

Editor's Note: DTN/The Progressive Farmer has a business partnership with FarmLink, mentioned in this story. That relationship created the new DTN MarketVision farm management program.

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

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Emily Unglesbee