The clattering farm tractors of yesteryear were uncomplicated
machines equipped with That's all you only a few accessories, all of
which could be easily maintained and repaired by the farm families
fortunate enough to own them. By contrast, today's mechanical descendants, rumbling across Nebraska's sugar beet fields, are often bristling with cabmounted
Navstar receivers, digital computers, full-color video displays, and electronic
database memories programmed with custom-tailored Geographic Information Systems.
The sugar beet is a delicate plant requiring protection during the early phases of its
lifecycle. Consequently, fast-growing cover crops - oats, barely, rye - are commonly
seeded throughout the same field just prior to the planting of the sugar beet seeds. Then,
when the sugar beets are being planted, a narrow stream of plant-selective herbicide is
laid down with the beet seeds to destroy nearby weeds while allowing the protective
cover crop to grow between the rows.
The local soil type and its organic content are of crucial importance in determining the
optimum quantities of herbicide to apply. Too much herbicide damages the delicate sugar
beets, too little allows weeds to grow and choke them within their rows.
Three different soil types are commonly found in close proximity in western Nebraska:
When all three soil types share the same sugar beet field, the optimum amount of
herbicide for effective results often varies as much as 50 percent.
- Sandy clay loam
- Coarse-textured sandy soil
Many of Nebraska's sugar beet fields employ center-pivot irrigation systems in which an
elevated self-propelled irrigation fixture pivots around a gigantic circle spraying water as
it moves forward. Some center-pivot units irrigate flat, circular fields a half-mile or more
in a diameter with practically no supporting labor.
Historically, the tractors planting sugar beet seeds have simultaneously applied uniform
amounts of herbicide to destroy any weeds beginning to grown along the narrow beet
seed rows. This compromise approach toward herbicide application is simple and easy to
implement, but because soil types vary so much within a typical circular field, it does not
achieve optimum results.
Fortunately, a Navstar receiver mounted in the cab of a tractor coupled with an onboard
GIS database can help the operator optimize the application of herbicides in various
portions of the field. Aerial photographs are used to pinpoint soil-type variations. These
images are then digitized to form contour maps which are, in turn, fed into an onboard
Differential navigation signals broadcast by local FM radio stations are used to fix the
current position of the tractor to an accuracy of 3 to 5 feet. Farming industry surveys
indicate that about 5 percent of America's large-scale factory farms now use GIS
technology to achieve substantial improvements in the application of liquid fertilizers and
"Each area of the field receives only those specific nutrients that are recommended to
produce the desired crop," explains John Mann, president of Soil Teq, Inc., of
Minnetonka, Minnesota. Everyone benefits from the high-tech approach. Costs are
lower, productivity is higher, and pollution levels in local streams resulting from
fertilizer-infused runoff quickly decline.