The best way to dispose of your manure slurry is by injecting the nutrients into the root zone of the crops.  This is traditionally done before the crops are planted or after the crops are harvested.

It is also effective to inject directly into alfalfa fields.  The small amount of roots that are severed by the process quickly regenerate and the resulting Nitrogen and nutrient boost creates alfalfa cuttings that surpass your previous yield tonnage (assuming similar weather conditions and rain or irrigation water.)

The video below shows continuous flow drag line application with a tractor and tool bar with 30" rows and 8" sweeps into a field with corn stubble.