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Fine-tuning agricultural inputs.

Agricultural Research Service and University of Missouri scientists are helping farmers prove the benefits of prescription farming--the newest trend in managing agricultural inputs.

Prescription farming means applying inputs such as fertilizer, herbicides, and irrigation water with more precision than has generally been used. Farmers routinely apply fertilizers using an average rate based on a field's past yield and condition.

But environmental concerns are prompting both researchers and growers to look at alternative farming methods that offer good yields and profits while at the same time reducing the use of chemical inputs.

"Soils vary from point to point within a field. Depending on the variability of soil fertility, different spots in a field could require much more or less fertilizer than the average," says ARS agricultural engineer Kenneth A. Sudduth, who is based at the University of Missouri at Columbia.

Applying inputs only where needed increases production efficiency and reduces the potential for contaminating ground or surface water. Sudduth views the prescription farming system as a three-step process.

"First, the farmer needs to collect data about soil variability within the field and pinpoint where that variability occurs. Then, the information is analyzed and used to develop a variable rate application plan. Finally, the farmer applies fertilizer or pesticide according to the plan," he says.

ARS and University of Missouri agricultural engineers are working on technology to make prescription farming systems more efficient.

Sensors Are Promising Tools

Sudduth and other ARS and Missouri researchers are developing sensors, investigating field variability, developing data management techniques, and modifying application equipment. Each of these represents a piece of the prescription farming puzzle that requires engineering research to make all the pieces fit together into an integrated, high-tech system that is easy for farmers to use.

Researchers have already made strides in developing electronic sensors for soil properties. These devices will help farmers map variations in a field more easily and with more detail than would be practical by hand-collecting soil samples.

"Even in fields where soils are similar, there can still be variations," says Sudduth. "For example, organic matter content can vary considerably, even within a soil type, and that content directly affects the amount of herbicide needed for good weed control. "Soils with more organic matter appear darker. This observation gave us the idea that we could scan a field with an electro-optical sensing device. Using sensor data, we can recommend a variable rate for soil-applied herbicides," says Sudduth.

Under a cooperative research and development agreement with a company in Springfield, Illinois, known as AGMED, Sudduth and ARS agricultural engineer John W. Hummel at Urbana, Illinois, developed a portable near-infrared reflectance soil sensor. The machine reads the amount of soil organic matter and moisture in less than 60 seconds.

They first tested soil samples in the laboratory and then took the machine into Illinois fields. Sudduth is now making some modifications to the sensor for improved reliability and accuracy. AGMED has a license to make and sell the machine, which has been jointly patented by the company and ARS.

Soil nitrate measurement is another important element in prescription farming. Hummel is at work on a sensor to measure nitrate levels for use in recommending variable rates for nitrogen applications.

Stuart Birrell, a University of Missouri agricultural engineer who is also working with Sudduth, notes that development of the sensors is lagging behind the rest of the technology needed for prescription farming. "While some of the other components of the system are already in commercial use, most sensor technology is still in the prototype stage at best."

What About Yields?

Another prescription farming project involves measuring yield variability. "Yields and profit are very important to farmers. Being able to accurately measure yield variability within the field helps the farmer decide how to apply nutrients and gives an indication of how well the prescription farming method is working," says Sudduth.

In 1991, he and University of Missouri agricultural engineer Steve Borgelt equipped a combine with a grain flow monitor that's sold only in Europe, With it, they monitored yield variability on test plots at the Missouri Management Systems Evaluation Area site near Centralia.

"We were surprised that the 1991 yields varied by as much as 50 percent within a 600-foot plot," Sudduth says.

For the 1992 harvest, the combine was equipped with a Global Positioning System (GPS) receiver to pinpoint its location in the field. GPS is a network of satellites developed and maintained by the U.S. Department of Defense. The receiver, mounted in the combine, receives signals from the satellites and pinpoints the combine's position to within 15 feet.

The researchers are also using a GPS unit after harvest, or the next spring, to locate spots in the field where soil samples are collected. The samples are then analyzed to help determine optimal fertilizer rates for the coming year. [For more on GPS, see Agricultural Research, February 1992, pp. 4-8.]

Missourians are known for their "show me" attitude. So, it's not surprising that Missouri farmer Bill Holmes, whose farm is located in the southern part of the state, asked ARS and University of Missouri researchers in 1991 to help automate data collection and manage data needed for the Missouri Agricultural Water Quality and Precise Application Project, which began in the fall of 1989.

Holmes is the driving force behind the project to demonstrate and apply prescription farming methods. The project includes 40 producers with 10,500 acres and several cooperators: the University of Missouri (Columbia), Missouri Department of Natural Resources, U.S. Environmental Protection Agency, and USDA's Agricultural Research Service and Soil Conservation Service (SCS).

To measure nutrient variations in their fields, Holmes and other farmers collected some 4,000 soil samples using a 330-foot-square grid.

After the University of Missouri soil lab analyzed the samples, Holmes loaded the results into a computer database along with information from a detailed SCS soil survey.

"Holmes also wanted to measure yields, and we've been able to help him do that with our instrumented combine," says Sudduth.

Preliminary analysis of the data taken in the fall of 1992 from one 160-acre field indicates yields ranged from 140 to 215 bushels of corn per acre.

The next step is to load the yield and soil data for the fields into a farm-level Geographic Information System (GIS) developed at the NASA-supported Space Remote Sensing Center in Mississippi. Birrell is helping programmers at the center incorporate advanced analysis techniques into the GIS.

The GIS is used to map and compare variability patterns in order to determine the best way to manage each field. Then, data can be directly transferred from the GIS to an automated fertilizer applicator to provide the correct amount of nutrients tailored to each area of the field.

The cooperative effort between Holmes and the researchers has been good for all. "We've been able to help Holmes implement a real world system, and at the same time we've been able to evaluate our technology and verify research findings under practical field conditions," says Sudduth.

What Happens Next?

Before prescription farming is widely adopted, farmers will need to know just how much it will help increase their yields if they switch to the new technology. To find out, ARS and University of Missouri researchers plan the ultimate test by planting side-by-side comparison strips using both average and variable rate applications of fertilizer. Crop yields, nutrient movement, and economic returns will be monitored and analyzed.

"We'd like to get an objective look at both yields and profits. The savings aren't necessarily realized from using less fertilizer or other inputs, but from getting the most yield from what is used," says Sudduth.

He adds that the prescription farming techniques available today require farmers or their custom applicators to invest a considerable amount of extra time and effort. Although research results are promising, it will likely be several years before the more integrated and easy-to-use systems attractive to a wide range of farmers are available.

Even so, researchers and progressive farmers like Bill Holmes are excited about the promise of a technology that offers increased profits and environmental protection.--By Linda Cooke, ARS.

Kenneth A. Sudduth is in the USDA-ARS Cropping Systems and Water Quality Research Unit, Agricultural Engineering Building, University of Missouri, Columbia, MO 65211. Phone (314) 882-4090, fax number (314) 882-1115.
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Author:Cooke, Linda
Publication:Agricultural Research
Date:Jan 1, 1993
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