Farm Horizons, May 1998

Technology allows farmers to manage small areas of fields


Precision farming, according to the University of Minnesota Extension Service, is applying the correct input at the correct rate at the correct time and in the correct manner.

It's farming by the foot. You break down the farm into small pieces and treat those pieces accordingly.

As any farmer will tell you, it's just not that simple.

"Today's technology, such as GPS (Global Positioning System) and yield monitors, have raised precision farming to another level," said Dave Schwartz, extension educator at the University of Minnesota Extension Service, Meeker County.

GPS is a satellite system that transmits longitude, latitude, and altitude signals which in turn pinpoint a position on earth within feet. GPS can also determine a location about every three seconds.

When utilized in farming, a combine, equipped with GPS and a yield monitor, can know its exact location in the field and what each section of the field is producing. That information is transferred to a computer and produces a detailed yield map of the farmer's field.

Using GPS in soil sampling, the field is broken down into grids and samples taken for each grid. The soil sample information then can be used to spread fertilizer via a sprayer equipped with GPS to treat the appropriate areas with the correct amount of fertilizer.

"It's the system of the future. This will be farming in the next century," said Pierre Robert, professor and director of the Precision Agriculture Center at the University of Minnesota.

"The concept began in the early '80s. We still need all the tools, like better software, to efficiently use all the data we're collecting in order to say what would be the most appropriate practices for site by site. But we are making good progress."

In Costa Rica, farmers were working with two-acre fields. They could see the viability of their fields but didn't know what to do, Robert said.

"Here, we have the capability to react to what we find," he continued. "Do the right thing at the right place at the right time."

To achieve that precision, good record-keeping is a must, said Robert. If a farmer can't remember what he did where and when, or what the weather was like at a given time, then yield maps won't be of much help to him. He wouldn't have any basis on which to draw conclusions about the varying yields the maps might show.

Robert explained that if a farmer noted when it rained, where he was in the field, and when he returned to the field, then he could draw some conclusions from his yield data. For example, if he returned too soon after the rain, compaction might be the result of the poor yield shown on the map.

Another consideration in precision farming is what size the soil sample grids should be. Often sampling is done in four-acre grids.

"The grid size is often driven by economics, not agronomics," said John Lamb, associate professor in the Department of Soil, Water and Climate at the University of Minnesota. "Agronomically, the smaller you make the grid, the better off you are."

The University of Minnesota recommends that grids should be no larger than 2.5 acres in the first year of sampling, said Robert. Better yet is smart sampling, not a systematic grid but a flexible grid as to the viability of the field, he added.

With accurate grid samplings, herbicides and fertilizer application can occur where needed ­ site specific.

Proponents of precision agriculture, or site specific management, point out that this is also environmentally sound.

Data overload

Paul Lasley, professor at Iowa State University, said in an article in the university's publication "Integrated Crop Management," that while GPS provides much site-specific data on fields that can improve application rates, there is a big gap between having the data, transforming it into useful information, and incorporating it into farming decisions.

Farmers can easily be on overload with the amount of data available to them and how to interpret it.

Schwartz explained that farmers can take their yield maps and overlay a soils test map looking for common denominators between yields and potassium levels. Drainage maps can be overlaid and correlations drawn between yields and poor drainage. A typography of soil type information can be correlated to the yields. Farmers can also look for similarities in soil ph and yields.

Most farmers he has met through precision farming workshops see it as a challenge, Schwarz said. The information they are getting surprises them. Most farmers, however, will need assistance in interpreting this data.

"Farmers have to be careful about jumping into hasty conclusions. It easy to jump at a wrong conclusion when looking at yield maps," cautioned Schwarz.

Precision farming enthusiasts agree that yields should be studied over several years before any decision-making. Weather, crop rotation, drainage, compaction or even machinery problems add more variables to the equation. Precision agriculture is still a relatively new science where data is still being compiled

"From reviewing yields, it's been determined that about 15 percent of each field is not farmable, but that 15 percent changes every year due to variables such as weather," said Schwarz.

"We're evaluating many different things working. It's difficult to make any decision," said Lamb.

Lamb studied yield pattern to yield pattern in the sand plains of Princeton for the past five years. The soil tends to be consistent there so the soil variability is removed. However, yields differed from 40 to 70 bushels throughout the patterns.

"We need to make use of the technology that is already there," said Schwarz. "We encourage soil testing every three to four years to learn the potassium and phosphorus levels, and apply fertilizer accordingly."

Another management factor is field drainage, added Schwarz. Draining low areas, better tiling systems or even pattern tiling every 60 or 90 feet can provide uniformed drainage. Good drainage improves the chances for the farmer to get in his fields early.

The economics

A farmer needs to ask: for every dollar that is put into the farm, what will the return to be on those dollars invested, said Karl Foord, extension educator at the University of Minnesota Extension Service, Dakota County.

In the precision farming, the returns can be slow. Sound decisions can't be made on one year of data. At least three years of data is needed, and with crop rotation that would mean six years.

Foord said the initial investment for a yield mapping system and computer is approximately $12,000. For a small farm, that's less acres over which to spread $12,000; a larger farm can absorb the costs somewhat better.

Other costs to be considered are: grid soil sampling analysis, fertilized spreading costs with precision technique, GIS consulting map interpretation and equipment depreciation.

Farmers should also consider what precision farming would cost beyond what they are already spending.

A 500-acre farm would need an almost 6 percent increase in production to break even while a 1,000-acre farm would need about a 5 percent increase in yields, said Foord. (A copy of this report is available by contacting Foord at 612-891-7700.)

Farmers can hope for a short return. Then, with the information they are developing about their farm, can make management decisions over time and hopefully see a return on their investment.

For insurance purposes, Foord said that yield maps are helpful to farmers. Yield swells on the map can be used to clearly show where there might have been hail damage.

The consensus isn't clear on the techniques of precision farming, Foord commented.

"We have a better understanding of field to field," said Robert. "Most farmers and colleagues are surprised by the viability (of fields). Corn yields can go from 100 to 180 bushels per acre. Farmers are losing money by overall application."

Who's practicing precision techniques?

Despite the initial investment, farmers are incorporating these precision principles.

Aside from crop management, precision agriculture is also used in livestock production, Schwarz said. Pork producers treat the nutritional needs of market barrows and market gilts differently, where at one time they were fed all the same. Dairy herds are identified by computer chips so the animals are individually managed and their nutritional needs individually addressed.

"Precision agriculture is not limited to big farms, but more related to the attitude of the farmer. There are those farmers who are always looking for something new or those who prefer to continue doing what they're doing," said Robert.

Presently, there are about 17,000 yield monitors in the United States, and that number will increase to 20,000 at year's end, according to Robert. About 40 percent of dealers and cooperatives are offering precision agriculture services such as soil sampling and fertilizing spraying.

Teply Equipment in Glencoe has installed 15 yield-mapping systems; Teply's Cokato office has installed four.

Users are not primarily young, said Keith Zajicek of the Glencoe office. Older farmers also realize they need to make their farms more efficient and are learning how to use computers. Teply also offers classes on Greenstar, John Deere's yield-mapping system.

One of our biggest users is Virgil Scherping of Metro Farms, said Zajicek.

Metro Farms installed its first yield-mapping system two years ago, said Curt Dvorak, farm manager.

"We use it in grid soil sampling, spraying and yield monitoring," said Dvorak. "We've been monitoring yields the last two years."

It's difficult now to see an increase in yields, but they do see a decrease in fertilizer cost, Dvorak added.

Metro Farms uses two-acre grid sizes for soil sampling. With the mapping system, they can zero in on areas low in phosphorus and with that information in their sprayer can fertilize accordingly. Previously, they soil-tested at the closest point to the field row and then treated the field on those soil tests.

"It's putting the right stuff in the right spot," said Dvorak.

Dvorak also iterates what Robert professes. Good records are essential to the success of precision techniques.

"We keep real good records of what we put where and when; we keep track of all our planting dates," added Dvorak.

When studying yields, you can't come to quick conclusions commented Dvorak. Low yields might mean tiling is needed, or there is a compaction problem. It tells you something is wrong but not what.

"GPS is a tool," said Dvorak. "It's no different than talking to an agronomist."

Not all farmers are ready to utilize that tool. Farmers are faced with deciding to jump in now or wait until costs go down. Farmers need to be record-keepers and all that data still needs to be transformed into useable information on which farmers can act.

"The technology is not for all people," said Lamb. "The bright spot to precision agriculture is that it makes farmers better record-keepers. But I'm not certain how much it's worth to the farmer."

All farmers are faced with the dollars they have to work with and what will get them the best yield. As one farmer commented to Schwarz, "I need to determine what's nice and what's necessary for our farm."

Want to learn more?

The University of Minnesota's Precision Agriculture Center will sponsor the fourth International Conference on Precision Agriculture, Sunday-Wednesday, July 19-22 at the Radisson Hotel Saint Paul, St. Paul. The conference will feature hands-on workshops and an A to Z track with "field-ready" information.

For more information, you can visit the Web site at or contact the University of Minnesota Extension Service, Wright County at 800-362-3667, or McLeod County at 320-587-0770.

So just what is GPS?

Global Positioning System (GPS) has revolutionized the way we navigate.

For strategic defense purposes, the U.S. Department of Defense began launching global positioning satellites in the 1970s. The result was GPS, a set of 24 man-made satellites covering the earth in precise orbits at about 11,000 miles out in space.

Each satellite carries a clock so accurate it varies only three seconds every million years. As many as 12 satellites are available for signal transmission and receiver reception at any one time. GPS uses these satellites as reference points to calculate positions accurate to a matter of meters.

A receiver (your GPS unit) measures the distance from three satellites for a two-dimensional position fix. Signals from four satellites add altitude giving you a three-dimensional fix.

However, for national security reasons, the Department of Defense scrambles the satellites' signals resulting in a distortion of calculations of about 400 feet. With a process called differential correction, GPS coordinates can be corrected to provide accuracy within meters.

Aside from being the keystone to precision agriculture, GPS is used in surveying and mapping, oil and gas drilling, automobile map routing, traffic congestion management, firefighting, earthquake prediction, fishing, bike touring, and hot air ballooning, to name a few.

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