How should be counted the leaves on corn

Each year, before application of postemergent herbicides, disputes over how to count the leaves correctly on corn begin among agronomists. Is it necessary to count the first smallest leaf, and what about the leaf that has just appeared from the sinus?

Determining the development stages of corn is important for several reasons. First of all, the correct counting of the number of leaves is necessary for the timely and safe application of the postemergent herbicide. Also, based on the phase of corn development, nitrogen should be applied during the growing season.

There are at least three methods for counting the leaves of corn:
1. All leaves are counted. In this case, all visible leaves are counted, including the tip of a leaf that has not yet bursted. In practice, this method is used less often.
2. The incurved leaves are counted. The method is often used before herbicide application. At the same time, only well-developed leaves are counted, which deviated from the vertical position, having deformed in the shape of a bow. Thus, one top leaf is often not counted.
3. Only leaves with a "collar" are counted. This method is recognized by most manufacturers of seeds and of plant protection products. The stages of vegetative growth of corn are marked by the letter V, after which the number of developed leaves is indicated. This takes into account fully opened leaves, which have a whitish strip at its base. Unlike the first method, in this case, two or three top leaves are often not counted.

It should be noted that in all the above methods the first leaf should be counted. Despite the fact that it is significantly shorter than the other leaves and has a rounded end, this is a real leaf, not a cotyledon (corn, like other cereals, does not have cotyledons). Under dry spring conditions, this leaf dries quickly and after the V5-V6 stage becomes barely noticeable. In order to determine the phase of development correctly, the first leaf should be counted, regardless of whether it remains in place or not.
Thus, it can be got a different number of leaves on the same plant by using different methods of counting. You decide by yourself, how the leaves on the corn should be counted. From our point of view, the last method is the most convenient. The international denotation of stages, as well as clearly defined critical phases of development make it easy to apply this method in practice.

For example, one of the important stages of corn growth is V5-V6, when the growing point comes out of the ground, and the plants form the corn ear and the next harvest. At this time, corn is very sensitive to stressful conditions that negatively affect potential yield. This is also the beginning of a period of intense mineral nutrition and accelerated nitrogen uptake. If we know the features of this stage, it is necessary to make a conclusion that it is better to apply herbicides before the V5-V6 phase, and nitrogen fertilizers – after this phase.