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GPS: Its Uses and Potential Are Growing

Global positioning systems (GPS) are widely available in the agricultural community. Farm uses include:
• mapping yields (GPS + combine yield monitor),
• variable rate planting (GPS + variable rate planting system),
• variable rate lime and fertilizer application (GPS + variable rate controller),
• field mapping for records and insurance purposes (GPS + mapping software), and
• parallel swathing (GPS + navigation tool).

PS and associated navigation systems are used in many types of agricultural operations. These systems are useful particularly in applying pesticides, lime, and fertilizers and in tracking wide planters/drills or large grain-harvesting platforms.

GPS navigation tools can replace foam for sprayers and planter/drill-disk markers for making parallel swaths across a field. Navigation systems help operators reduce skips and overlaps, especially when using methods that rely on visual estimation of swath distance and/ or counting rows. This technology reduces the chance  of misapplication of agrochemicals and has the potential to safeguard water quality. Also, GPS navigation can be used to keep implements in the same traffic pattern year-to-year (controlled traffic), thus minimizing adverse effects of implement traffic.

Use of GPS navigation in agrochemical application with ground equipment has grown rapidly, and commercial applicators are quickly adopting the tool. According to a 2007 survey of those who offered custom application (Whipker and Akridge, 2007), 82 percent applied at least some of the fertilizer/chemicals using a GPS navigation system with a manual-control/light bar  guidance system. Twenty-nine percent said they used a  GPS navigation system with an auto-control/auto-steer guidance system for at least some of their custom application. On average, for all custom applied materials, percent was applied with GPS light bar, and 12 percent was applied with auto-steer GPS. GPS navigation has  become standard practice for U.S. aerial applicators. Crop producers are also starting to adopt these systems, because GPS navigation is an excellent way to improve accuracy, speed, and uniformity of application.

Selecting GPS Components

  • Real Time Vs. Post Processed
  • Do you need to know where you are right now?
  • Number of Channels
  • More channels means better selection of satellites.
  • Differential Correction
  • Method to improve position accuracy

Parts of a Complete System

  • Antennae
  • Receiver
  • Display
  • Storage
  • Interface

Soil Sampling

  • Georeferenced soil samples can be collected
  • Sampling Methods:
  • Grid sampling: intensive sampling of entire field
  • Directed sampling: intensive sampling of particular target areas

Grid Sampling

  • Data collected for  each cell or point
  • Multiple samples combined into each cell or point  sample

Directed Sampling

  • Sampling zones established based on knowledge of field
  • GPS used to locate sample points.
  • Areas of interest intensely sampled, others lightly sampled

Yield Maps

  • Record of spatial yield variability within a field or farm.
  • GPS data coupled with yield data to produce map.
  • Mechanically harvested
  • Hand harvested
  • Useful tool for decision making

GPS navigation has many advantages over conventional marking devices such as foam markers, and especially over the visual-estimation method for spinner spreaders. With an existing GPS being used for yield monitoring or field mapping and soil sampling, the GPS navigation system can increase the efficiency of the farm or agribusiness while minimizing adverse environmental impacts associated with overlapping  applications. The system can also reduce operator  fatigue and anxiety regarding fertilizer and pesticide application. Finally, use of this technology can demonstrate to the nonagricultural community that advanced  technology is being used to farm efficiently and safely.

The advantage of “as-applied” maps, provided by some systems, is documentation that applications were made at the appropriate location and rate.

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