To the extent that yield variations can be associated with nutrient supplies or pest populations, management inputs can be varied accordingly. A GIS system is basically a software which is vital to the storage, retrieval, and superpositioning of data that are gathered. When used in combination, these three technologies allow the yield for any small area or location in the field to be graphically recorded and subsequently displayed in the form of a map. The Yield Monitor and the GPS guidance system can be mounted on top of a combine. Then the exact position and the corresponding yield measurements can be continuously detected and recorded for subsequent analysis.
Farmers can generate precise yield maps, showing yield variations across fields.
Once areas with low yields are mapped, the GPS guidance system can be used to locate exactly the area for sampling, analysis, and problem identification. Soil sampling becomes a major issue for Site Specific or Precision Farming to the extent that nutrient concentrations in the soil may account for yield variation and can be modified to the advantage of the farmer. Soil samples should be obtained to truly reflect the nutrient level and other physical variability in different parts of the field, so a corrective action can be taken. Information from soil tests can be used to generate a map of soil fertility status. Obviously, to take advantage of the technology, and to determine whether variation in soil fertility is causing yield variation, soil sampling for Precision Farming requires a much different sampling strategy than normal.