These creatures are millipedes.  They are arthropods not insects.  Millipedes feed on decaying organic matter in the soil.  This field likely has high organic matter in the soil and the right moisture provided the environment for the millipede population to grow.  They also are commonly found congregating in the fall.  I do not believe there is any need to control them out in a field.  Most articles on millipedes are focused on preventing them from being an indoor pest.  Please see the following article from Michigan State University on millipedes.

http://www.pestid.msu.edu/insects-and-arthropods/millipedes/