VARIABLE RATE APPLICATION SYSTEM

A variable rate fertilizer spreading apparatus for spreading a precise amount of multiple types of fertilizers upon a field based upon a location in the field. The system comprises a controller accessing a soil map indicating the type of soil for each portion of the field, several fertilizer maps storing the desired fertilizer level of each of the fertilizers stored in product bins on the tractor, and several status maps each indicating the current fertilizer level at various locations of the field to be fertilized. By accessing the speed of the tractor via a speed indicator, and ascertaining the location of the tractor in the field via a position locator, such as an LORAN or GPS system, an expert system determines the dispensing rate of each of the fertilizers based on the various maps and the position and speed indicators such that the proper dispense rate of the fertilizers from bins is set to attain the desired level of fertilizers. The expert system accesses standard and proprietary data tables and processes complex calculations taking into account the interaction effects of multiple fertilizers being dispensed upon a particular type of soil, as ascertained from the soil map. Thus, each portion of a field can be characterized and fertilized such that the resulting level of each of the fertilizers matches the fertilizer maps after spreading fertilizer, where no predetermined path of vehicle is necessary. The current fertilizer level map is updated after a dispensing pass to provide a real-time record.