Growth and Management

Abstract

K nowing the growth stages of corn allows growers to time field operations properly to meet windows of opportunity. Proper timing of fertilizer, irrigation, cultivation, harvest, and insect, weed and disease control can improve yields significantly. Knowledge of the plant growth process provides the means to enhance the corn crop. Plant symptoms occurring during certain growth stages help the grower determine the cause and effect of a deficiency, disease or other crop problem and take timely measures. Producers have several methods of staging corn. The leaf collar method uses a counting system of "collared" (when the leaf partially unclasps the stem or culm) leaves during the vegetative growth stages and includes the first emerging round-tipped leaf in the count. This is the most commonly used staging method. Another less common method is similar but does not count the first emerging leaf, only the later, pointed-tipped leaves. A third method of staging commonly is used by the crop insurance industry and simply counts all leaves visible, whether rounded or pointed and collared or not. Knowing the staging method used to describe the stage of plant growth is essential. Herbicide labels that don't refer to the leaf-collar method may (or may not) skip counting the first true leaf (rounded-tipped leaf). To clarify, some labels may refer to the height of the weeds for application timing. Being off one or two leaf stages due to differing descriptions may not always be critical, but it can lessen the treatment benefits and create confusion in interpreting labels, troubleshooting problems and dealing with others, such as insurance adjusters. Consistent staging descriptions can help apply herbi-cides at the right time and avoid crop damage. Vegetative Stages Reproductive Stages VE (emergence) R1 (silking) V1 (first leaf) R2 (blister) V2 (second leaf) R3 (milk) V3 (third leaf) R4 (dough) V(n) (nth leaf) R5 (dent) VT (tasseling) R6 (physiological maturity)