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Corn+Soybean Digest

Nail Down Yields Early

Most of us are skittish about selling much of our new crop until we have a good sense for how it will yield. Mike Emens of Frankfort, IN, has a leg up on most of us. He subscribes to a satellite photo imagery service that helps project his yields in August within 10% of the final yield.

“I have limited on-farm bin storage,” says Emens. “So forward marketing is important for me. Getting accurate yield figures in August is a real boon for my marketing.”

Infrared (IR) imagery helps make accurate yield projections by identifying the locations for in-field yield sampling that will most accurately predict the field's final yield, says Justin Welch, agronomist and technology manager for Co-Alliance LLP, Danville, IN, which provides Emens' imagery.

“The imagery guides you to an assortment of different yield areas, and provides the percentages these areas make up in the field, giving you a more precise estimated yield for the field,” says Welch. “Without the imagery, you might take your yield samples from all the best areas of the field, or maybe all the poorest areas. Neither gives you an accurate estimated yield.”

Marketing is just one reason Emens uses the imagery service. His main interests in it are to better monitor his corn and soybean crops during the growing season, and to fine-tune his hybrid selection and fertility program.

IR imagery measures plant chlorophyll differences to identify non-crop vegetation, such as weeds and crop stress. Stress can be caused by low soil fertility, insects and disease, weeds and too much or too little moisture. IR imagery can also detect stand uniformity problems as well as tillage and compaction problems.

Many of these factors aren't easily detected from the ground, but are easily seen in shades of red and green on the IR maps. Subtle patterns of compaction, for example, are almost impossible to see from the ground.

Emens no-tills all of his cropland and is careful to stay off it until it's fit to drive on, but the imagery still picks up where machinery traffic had been greater on the edges of the field and by the field entrance. “I also could see where the tile lines were from the imagery picking up differences in the vegetation,” says Emens.

Imagery is especially useful when it identifies problems during the growing season that growers can fix. It revealed a 10-acre area where Emens' corn wasn't keeping up. He quickly learned that the row starter had not turned on during planting, leaving the area short of nitrogen (N). He was able to sidedress anhydrous ammonia in that area to rescue it.


“Images are taken throughout the growing year, from about a month after planting until full maturity,” says Welch. “Growers can choose between having their fields' images taken from a plane or from a satellite. They receive about twice as many images during the growing season for the same money from the satellite. However, images taken from a plane have a better resolution, providing more detail. And we have more control over when the plane takes its images.”

That timing can be important in a year with cloudy weather. Welch explains that images need to be taken on a clear day, preferably between 10 a.m. and 2 p.m. The satellite is overhead Indiana during those time spans about every fifth day. A plane, on the other hand, can be sent up any day.

During June 2009, there were only four days when the sky was clear enough over central Indiana to take images, says Welch, and two of these days were early in the month when the crop was too small. So in such a year with lots of cloud cover, the plane service works out better, says Welch. In the end, all growers receive the number of images promised. AgSure's growers pay $3/acre for the service.

For that price it provides the images and an agronomist to help growers understand them. AgSure sends Emens the images electronically to download onto his computer. He transfers the images to a handheld computer with GPS that he then takes to the field to walk problem areas where weeds, drainage and other problems showed up.

“You have to walk to identify the problems,” says Emens. For example, the imagery identified a weed patch in one of his cornfields. “With the handheld I was able to walk to it and see that it was a spot the sprayer had missed. I was able to take care of it with a hand sprayer. Without the handheld, I don't know if I could have found the spot. You get out 20 rows or so in standing corn and you can lose your orientation,” says Emens.

Welch says the handheld computer with software and GPS costs around $750. Some growers, such as Emens, own their handheld computers and walk their own fields. Most, says Welch, choose to have an AgSure agronomist walk the fields to check out problem areas. While AgSure agronomists will review maps with farmers as part of the fee, there is an additional charge if they are asked to walk the fields.


Emens is in his second year with the service and plans to evaluate its benefit after second-year results are in. This gives him a look at what it has showed over a full two-year corn-bean rotation. “I'll spend the money up front to evaluate the value of this service, but in the end it will have to pay.”

Welch urges growers not to judge the service solely on being able to find problems, such as areas missed by spraying or a clogged tile line. Farmers will find that its greatest value is in helping them determine the most profitable long-term management practices for their fields, such as the best tillage system and matching fertility programs with corn hybrids.

Welch explains that each corn hybrid has a distinct preference as to when it needs the most N. Some hybrids or families of hybrids need a lot early in the season, some later. You can optimize yield by selecting hybrids that dovetail with your N application schedule.

By using IR imagery, Welch says you can watch the corn crop develop throughout the season and see if the hybrids you selected are getting the N they need when they need it. He also recommends planting check strips to compare hybrids and fertility programs.

Over time he says you can fine-tune hybrid selection and soil fertility by field for optimum yields.

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