Classification of corn plant matter bales is based on three distinct features of how the bales are formed.  First classification pertains to the composition of the bale material, second classification refers to the number of equipment passes made on the field to get the corn plant matter into a bale, and geometric shape of the bale comprises the third classification.

Classification based on Composition:

Parts of a Corn PlantMaterial Other than Grain (MOG) typically consists of corn plant (Figure 1) parts that pass through the combine.  This material is spread back on the land when it exits the combine in the case of grain harvest.  The amount of plant material left standing depends upon the height of cut used to combine the corn plant. The material left standing can be shredded or chopped to increase the removable amount of plant matter.  Combine header’s settings including height of cut and chopper adjustments, and combine spreader settings define how much material becomes available to be baled.  In addition, equipment can be specifically targeted towards certain parts of the corn plant to increase their content in the final composition of the material baled.  Terms such as MOG bales, cob bales, stalk bales, and stover bales thus identify the general composition of the corn plant matter bales.

 MOG bales typically are formed by dis-engaging the combine spreader, allowing the material to be dropped in a windrow to be baled later.  MOG material typically consists of the plant matter at and above the corn ear (Figure 1), i.e. the material above the height of cut.

Cob bales are formed where the plant matter baled  comprises of a higher percentage of cobs than the MOG or Stover bales.  

Stalk bales typically  are comprised of the plant matter left in the field after the MOG bales have been removed.  In this case, stalks are chopped or shredded and augured or raked into a windrow for baling. 

Stover bales comprise the majority of the above ground plant matter for a corn plant including the stalks and MOG material.

Equipment settings and operation influence the final composition of the material in the bale.

Classification based on Equipment Passes:

This classification refers to the order of the baling operation resulting in formation of corn plant matter bales.

Single Pass Bales:  These bales are formed by directly collecting the plant material as it exits from a combine without allowing the material to drop on the ground.  The baler is towed behind the combine to eliminate any subsequent passes for baling the material. Publication PM 3051C - Single-pass Harvesting Technologies provides an in-depth look at how this strategy works.

Second Pass Bales:  These bales are formed when baling occurs after the combine has passed through the field.  The spreader at the back end of the combine is disengaged to allow material to drop on the ground into a windrow.  Stalk stompers, mounted beneath the combine head, may be used to flatten the standing stalks before the material drops from the combine.

Third Pass Bales:  In this case, baling is the third operation starting with combining first.  The second pass in this case is with a windrowing shredder that chops the standing plant matter simultaneously creating a windrow for baling.

Multi-Pass Bales:  The bales that are formed with more than three equipment passes.  Operational efficiencies are greatly reduced when producing multi-pass bales.

The material can be formed into square or round (large or small sized) bales depending upon the type of baler used.