Variable Rate Technologies (VRT) and GPS referenced field operational data are the driving technologies behind Precision Agriculture.  These technologies are relatively new to production agriculture and are rapidly expanding the capabilities of Precision Agriculture systems.  Farmers, farm managers, and crop consultants can use these tools to maximize production by zones within a field by moving crop inputs from zones where they may not be needed to zones where they are lacking. 

The University of Nebraska - Crop Watch: Precision agriculture tools and information is an excellent site that for detailed precision agriculture information and precision ag. tool and techniques.  Click on the following link to go to the Crop Watch: Precision Agriculture website.  http://cropwatch.unl.edu/web/ssm/home

Currently, VRT is focused on field nutrient management but variable seeding and pest control are not far behind.  For example, fertilizer applied at a flat rate to a field may over fertilize areas or zones of high fertility and under fertilize those zones that are low in fertility.  Using precision ag systems, a producer can variable rate the fertilizer application by zones and move fertilizer from zones high in fertility to areas that typically would be under fertilized.  The amount of fertilizer applied to the field may not change but the distribution of the fertilizer within the field does.  This VRT fertilizer management system not only is more effective but it also reduces potential environmental impacts.

Precision Ag and VRT rely on the construction of manageable zones within the field.  Several approaches are currently available.  These are: