One of several requirements for uniformly quick germination in corn (Nielsen, 2007a) is uniformly adequate soil moisture in the seed zone. When seedbed soil moisture is variable (too dry vs. just right or too wet vs. just right), germination and emergence will also be variable.

Corn planted during the past couple of weeks in parts of Indiana has occurred in soils that have dried quickly in response to a string of warm, sunny days with strong winds and low humidity levels. Tilled seedbeds in particular have dried very quickly at the surface and sometimes unevenly.

Coupled with shallow compacted tillage layers that sometimes prevent planter row units from placing seed as deeply as the depth setting targets, kernels within inches of each other in the seed furrow can experience significantly different soil moisture levels. In other situations, growers may have neglected to change planter depth settings in response to the depth at which soil moisture was more uniform.

Last Friday I came across an example of fairly dramatic uneven emergence caused by variable soil moisture in a conventionally tilled field (corn following soybean) that was planted May 7. I estimated 75 to 80% of the field was comprised of “normal” emergers that were at the late V1 leaf stage (one leaf with a visible collar). Some late emergers were barely breaking through the surface, while others were yet in the process of elongating towards the soil surface.

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