Using corn growth stages to maximize yield
Management strategies for improving corn yield are most effective when you can identify the growth stage in which potential yield is affected. For example, the effects of fertilization, frost or hail, moisture stress, plant diseases, insect injury, and pesticide application on yield will be determined by the growth stage in which these events occur.
How to identify growth stage
Corn growth stages are classified as vegetative (V) or reproductive (R). The leaf collar method is one method used to stage corn while it is in vegetative stages. With this method, the vegetative stages are based upon the number of visible leaf collars. Staging begins at emergence (VE), and each new leaf with a fully developed leaf collar is called stage V(n). Vegetative leaf staging for corn plants ends when the corn develops a tassel (VT); once the plant has silks visible outside of the husks it has reached the first reproductive stage (R1).
Vegetative and reproductive stages are determined on a whole-field basis when at least 50% or more of the plants have reached or are beyond a particular stage.
NOTE: Click on the thumbnails to enlarge the photos.
CORN GROWTH STAGES
|Image of stage||Description of stages|
|VE||Emergence – shoot (coleoptile) has emerged from the soil|
|V1||First leaf – lowest leaf has a visible collar; this leaf has a rounded tip|
|V2||Second leaf – two of the lowest leaves have a visible collar, the second and subsequent leaves have pointed tips|
|V(n)||nth leaf – “n” leaf collars present, most corn hybrids produce between 18 to 21 leaves|
|VT||Tassel – lowest branch of the tassel is visible|
|R1||Silk – one or more silks extends outside of husk leaves|
|R2||Blister - kernels resemble “blisters” with clear liquid|
|R3||Milk – kernels filled with “milky” fluid|
|R4||Dough – inside the kernels are a “doughy” consistency|
|R5||Dent – dent forms on kernel and milk line progresses towards kernel tip|
|R6||Physiological maturity – kernels at maximum dry matter accumulation; a “black layer” will form at kernel base (2-3 days after physiological maturity)|
The description of corn growth stages are taken from the following Iowa State University publications: