Yield monitors in cotton: USDA-ARS researchers seek instrument accuracy

Precision agriculture will prove its worth when companies offer instruments that are less specialized than are guidance systems and yield monitors currently on the market.

The key to farmer acceptance, says Alan Brashears, USDA research engineer at Lubbock, Texas, is efficiency, a machine that does more than one thing. “We need to use the same equipment for multiple crops and to gather more information than just yield,” Brashears says.

“We should use a guidance system, for instance, to survey or pinpoint specific areas in a field, measure acreage, and establish field borders. And we need instruments that will do more than monitor yields. Currently, most of our precision agriculture equipment is specialized, yield monitors and guidance systems.”

Brashears says initial research from precision agriculture technology may reveal uses that are more valuable than the original intent. “Like most things, the research spinoffs may be more important than the main target.”

He says nitrogen measurements, for example, could prove more useful to farmers than yield evaluations.

Meanwhile, the quest for an accurate and dependable cotton yield monitor continues across the Cotton Belt.

“We're looking at four different units,” Brashears says. Two of those are stripper-mounted units. One depends on a weighing system; the others use light sensors.

“Weight units and light sensors offer advantages and disadvantages,” Brashears says. “The weigh system, for instance, is easier to calibrate. A farmer can do it in the field. But installation requires modification of pivot points on the stripper basket. It's expensive and not particularly easy to install.”

“Cotton farmers also want to measure weight and yield and this unit was not always consistent,” Brashears says.

Light bars are easier to install. Brashears says Alex Thomson, a Mississippi State University researcher, is working on light sensors with the light source and receiver mounted on the same bar. He says units are more available for pickers than for strippers. Commercial companies likely will market two units, both light sensors, this year, Brashears says.

Light sensors demand proper installation and maintenance. “Field cleaners may pose problems. If farmers remove them or shut them off, no cotton is going through so they are not sensing. Installation before the field cleaners seems to work well.”

Keeping light sensor lenses clean may provide a challenge. “Units are installed in dirty, dusty places and may not work properly if a piece of lint gets in the eye. Trash builds up on the lens. Design modifications help, but farmers still need to check lenses at least once a day during harvest. If the unit stays clean, it can come within 5 percent of actual weight.”

Calibration is more difficult than with a weigh unit. “We have to get a weight for the trailer, module, etc., and then adjust calibration back from that baseline. Farmers may wait several days to get weights back from the gin.”

Brashears says growers also have to convert seed cotton yield to lint yields. “Gin turnout is a factor and we'll need to do some additional bookwork after harvest.”

He says the light bar units “are pretty close to being ready.” He also advises farmers to be patient. “They need some computer savvy, but companies are improving both computers and software.”

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