unimproved stepper realization the distribution rate becomes granular available only at discrete rates particularly at slow rates in these systems slow rates are extremely important as the mower slows to reverse direction or to accommodate terrain conditions since the servomechanism is microcomputer based parameters that vary only at setup time can be easily input and retained for the duration of the setup parameters can be input by the mower operator by keypad and or captured in other well known ways for example the viscosity temperature profile of a number of materials can be retained in the system the operator would need only to key in the identification number of the materials alternatively the number can be entered by scanning a bar code on the material container with a wand attached to the computer field set up of integer multiples of base distribution rates are achieved by the modular pumping package fig1 and 18 in a specific agricultural operation the fluid to be dispensed and a desired distribution rate is specified be the agricultural objective a growth rate fertilization need herbicidal need etc referring to fig1 field set up proceeds as follows 1 referring also to fig9 after removing the module from the frame 72 by removing the pin snap 76 the housing parts 26 and 28 are separated by grasping the elastic hasp 34 c.