The 440 will do it.  You will need a shaft speed encoder on the metering shaft, hooked up to the flow meter cable.  Then you will have to put in a guesstimate cal number and try it, then adjust the cal number by the % error as you would any other calibration in order to find the proper cal number. 

As I understand it, the only difference between the 440 and the granular controllers from Raven is that the granular units have a provision to set the gate height and the 440 does not.  You will have to adjust the cal number proportionally when you change the gate opening.  For most fertilizer applications you should be able to set one gate height and just vary the rate using the controller which is going to control apron speed.  The exception would be if you want to go from applying tens of lbs to applying tons...in which case it would probably be necessary to change the gate height.