Understanding what goes on within a corn plant is important to your final yield.  In order to track your corn’s growth progress, we use a standard Developmental Stage Key.  The Vegetative Stage of corn is noted by the letter V. As each leaf unfurls from the whorl, a collar is formed.   These collars are numbered 1, 2, 3, 4, 5, etc.  V6 corn might have 7-9 leaves depending on how you count and how fast the corn is growing – hence the reason to reference collars.  There are 3 main segments to the V staging that are critical in determining what your corn yield will be:

V5 – the number of potential ear shoots is determined.

V6-V8 – the number of potential kernel rows are determined.

V8-V15 (approx.) – the number of potential kernels per row is determined.

Stress, both environmental or farmer inflicted, can cause catastrophic results.  For example, drought stress or an application of herbicide at V7 (approx. 8-9 leaf) that the crop cannot tolerate could cause a reduction in kernel rows.  If the corn moved into V8 before the stress was removed, reduction of the number of kernels per row could also occur.  Reducing 2 kernel rows and 10 kernels in length means a 6.7 bu/ac loss (2 kernel rows x 10 kernels in length x 32000 plants/ac ÷ 95000 kernels/bu).

A great tracking tool that I use can be found here.  Register your fields and track your activities with the corresponding growth milestones! 

Kirk Van Will, CCA-ON, Maizex Seeds Yield Specialist, West Middlesex & Lambton Counties
Twitter: @KirkVanWill