Feb 28, 2002

Tractors, Satellites, and Pickup Trucks




The tools of agriculture are changing as growers experiment with new space-age techniques called
"precision farming."




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February 28, 2002: Neal Isbell prepares for his workday by loading his trusty pickup truck with the everyday essentials of farming: his cap, jacket, extra boots, a box lunch and his dog. And don't forget the laptop computer and a GPS receiver.


"The laptop is now an essential part of our farming operation and I have a hard time keeping the dog from stepping on it," laughs Isbell.

Isbell's family has been farming in northern Alabama for six generations -- but Isbell isn't running the farm as his forefathers did. He is one of a new generation of growers called "precision farmers."

Above: A tractor with hooded sprayers treats a field with carefully-directed herbicide. Courtesy USDA.

Precision farmers use data from satellites and high-flying aircraft to pinpoint problems with drainage, insects and weeds. They learn where fertilizers are needed -- and where they're not needed. They discover pests -- and spray only the infested areas. It's a remarkably "green" approach to farming that is both friendly to the environment and profitable to the farmer.




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"We're seeing some real savings in fertilizer applications," says Isbell, "and our fields are more uniformly productive than ever."

Despite the advantages of precision farming, however, growers like Isbell remain uncommon. Many farmers simply don't know the technology exists, while others aren't convinced that it makes economic sense.

Hoping to change that, NASA launched a program in 1999 called Ag20/20 -- an industry-government partnership led by NASA and the United States Department of Agriculture (USDA). "We're educating farmers about precision farming technology and we're collecting hard evidence that it pays for itself," explains Rodney McKellip, who directs the program from NASA's Stennis Space Center in Mississippi. Ag20/20 partners include the National Corn Growers Association, the National Cotton Council, the United Soybean Board and the National Association of Wheat Growers.


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Ag20/20 has dealt mainly with corn, soybeans, cotton and wheat, "because those are the four biggest agricultural commodities in the United States," says McKellip. This year, though, the program will "branch out" to include orchards in Florida and Washington, and perennials -- like cranberries and blueberries -- in the Northeast.


Left: Computerized controllers and navigation systems for precision agriculture line the cockpit of this "

." Courtesy Rodney McKellip, Ag20/20


Precision farmer Neal Isbell is a cotton grower with 4200 acres under his care. Such expansive farms are difficult to canvass simply by walking or driving across the fields; they benefit from the "big picture" a satellite or an aircraft can provide.

"We use commercial satellites, like Ikonos and QuickBird," says McKellip, "as well as cameras mounted in aircraft." Sometimes NASA lends one of its own aircraft to the cause, but more often Ag20/20 encourages precision farming teams to use local flying services -- for example, Agri-Vision, a company in Columbus, Indiana, that collects digital images for agriculture in the Midwest.

The cameras used for precision farming are not ordinary. They can photograph a field as it appears not only at wavelengths of visible light, which the human eye can see, but also at near-infrared and thermal infrared wavelengths.


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Above: (left) an airborne infrared image of a cotton field exhibiting substantial variations in crop condition. (right) a Normalized Difference Vegetation Index of the same cotton field. Dark greens indicate areas of highest crop vigor, oranges indicate lower vigor. Courtesy Rodney McKellip, Ag20/20

"We find that near-infrared images are often the most useful for diagnosing the condition of a crop," notes McKellip.

Charles Hutchinson, of NASA Headquarters' Office of Earth Science, explains: Plants are good reflectors of near-infrared rays from the Sun. When the cells in leaves are healthy and turgid, they scatter near-infrared radiation in all directions. But when leaves begin to wilt -- because of stress caused by arid soil, pests or disease -- they become less reflective. "Stressed out" crops appear as darker-than-average spots in near-infrared images.

"The near-infrared part of the electromagnetic spectrum is more sensitive than visible light [to small changes in crop vitality]," continues McKellip. As a result, near-infrared images can pinpoint trouble spots before they become obvious to the human eye.


Once trouble spots are identified, a farmer might send out a human scout to see what's wrong. For example, Neal Isbell recently dispatched scouts across his farm to collect soil samples. "We used GPS receivers to keep track of our positions," says Isbell. The samples revealed a pH imbalance in some areas -- easily corrected by adding lime to the soil.

Left: an airborne infrared image of a healthy soybean field exhibiting little variation or stress. Courtesy Rodney McKellip, Ag20/20

Farmers have long known that growing conditions weren't the same at all places on their farms, yet until recently they had little choice but to treat their fields uniformly with "one size fits all" solutions. "These days nearly all new farm equipment has, as options, computerized controllers and GPS-guided navigation," says McKellip. "These devices have the ability to turn a sprayer, for example, on and off as it passes through a certain area of a field. This wasn't the case ten years ago."

One of the most important challenges for precision farming is getting data while it's still fresh. Farmers with rapidly growing crops need to know the state of their fields now, not days or weeks ago. Aircraft are still the best in this regard. McKellip explains: "An airplane can take pictures any time the weather is clear, but a satellite only passes over a field at a certain time on certain days. We typically get computer-processed data from airborne systems back to the farmer in as little as 24 hours." Satellite images, which require more time to downlink and process, can take from 2 to 7 days to reach a farmer.


Such delays won't be a problem forever, though. "Technology is advancing quickly and more of these commercial satellites are being launched each year," he added.


Right: This PDA displays a map of crop stresses. Note the attached GPS receiver. Courtesy Rodney McKellip, Ag20/20

Indeed, perhaps only a decade or so hence, Isbell will climb down from his tractor holding a palm-sized computer in direct contact with Earth orbiting satellites. The screen will reveal a map of crop stresses only minutes old. A few buttons punched ... and automated systems rush to trouble spots spraying precise amounts of pesticides, fertilizer, and water.

Satisfied, he'll glance around his burgeoning field. "But wait," he wonders, suddenly puzzled, "where did my dog go?" Fingers snap. "I must've forgot his GPS collar again!"

Perhaps some things will never change....


Web Links and More

AG20/20 -- A Remote Sensing Product Development Partnership for Agriculture

Ag20/20 Partners -- NASA Earth Science Applications Directorate; USDA Cooperative State Research Education and Extension Service; more


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The optical properties of leaves -- scientists must understand how plants reflect electromagnetic radiation to make sense of optical and infra-red maps used by precision farmers.


Right: the

of this plot shows the typical reflectivity of plant leaves at optical and infrared wavelengths. Healthy leaves are of near-infrared radiation. Courtesy Charles F. Hutchinson, NASA HQ.

How do farmers use remote sensing data? Here are two examples:

Tracking Pests: "Insects will infest the healthiest, most vibrant portion of a cotton field first," says McKellip. "That's the area that they're drawn to start their colonies." Using infrared imaging, the farmer can identify the most vibrant areas and direct treatment accordingly. "In this instance, we're predicting wthe insects should be."

Precision Weeding: "The time a soybean grower will spray for weeds is early in the season when the plants have not emerged too much," said McKellip. Vibrant vegetation detected by infrared imaging in this early stage is not soybean plants but weeds. "You can apply a broad-spectrum herbicide, like Roundup, spatially variable to areas of strong vegetation return."

Precision Farming -- a feature article from NASA's Earth Observatory

Precision Farming -- more information from the Global Hydrology and Climate Center.

NASA applying space technology to help farmers diagnose fields -- (Science@NASA) To water or not to water? Or fertilize? And how much? These and dozens of other questions nibble at farmers as they go about the business of raising crops.

Water-Witching From Space -- (Science@NASA) Farmers will soon have a new tool for getting the most out of their fields. NASA's Aqua satellite will provide crucial information about the water in the ground and the weather on the horizon.


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