For mobile tank fertilization of row-crop fields, methods and apparatus for improvements in multi-port fluid dispensing. The inventive methods and apparatus allow for replacement of a single regulating valve for the whole multiplicity of spray nozzles with a plurality of self-coordinating, closed-loop controlled, metering valves, but which closed-loop controllers maintain backward compatibility with existing gross flowrate control technology for the now-replaced and omitted single regulating valve. The inventive methods and apparatus can have closed-loop controlled multi-port metering valves for distributing fertilizer fluid to sub-sets of the multiplicity of nozzles, or else a dedicated single closed-loop controlled metering valve for every single one of the nozzles.