In the video in the last post, I mentioned the stages of growth in which the corn on the early- and mid-planting plots are right now. What does the V or the R mean in terms of the growth stages? How can I tell in what stage the corn is? In what stage will the corn be when I visit our plot this fall? Let’s talk about it.
There are two main stages of development in corn growth: Vegetative (V) and Reproductive (R). The vegetative stage begins at emergence (VE stage) and lasts until the tassel is fully developed. The reproductive phase begins when the silks emerge and lasts through physiological maturity.
During the vegetative stage is when the leaves of the corn plant grow. Emergence, or VE – when the corn plant emerges from the seed – marks the beginning of this phase. Following VE, most of these stages (V1, V2, etc.) indicate how many leaf collars – which is the lighter-colored band at the base of the leaf – are present at that time. So in V3 stage, three leaf collars (and three leaves) would be visible.
About a month after emergence, the nodal root system (more about roots in a past post) is established by V6, and the beginnings of a corn cob is present by the V6 growth stage. It’s around the V6 stage that the corn plant starts to go through a serious growth spurt. Back when you were probably in middle school, you may have grown a few inches in a short amount of time. Do you remember constantly feeling hungry? That’s because your body needed more inputs (food, etc.) to grow. Similarly, corn is particularly hungry and thirsty during this point in its growth, so it’s critical that plenty of water and nutrients are available for it to grow well. This is why we apply side-dress nitrogen applications around the V6 stage.
The tassel fully develops approximately eight weeks after emergence and signifies the last part of the vegetative stage, or VT (T indicating “tassel”). It is at about this same time that the silk on the corn cob emerges and readies itself for pollination. This begins the reproductive stage of development for the corn plant, or R1.
The rest of the reproductive phase is as follows:
R1: Silking – The silks emerge. Pollination takes place.
R2: Blister – The silks begin to darken and dry out. The moisture content in the kernels is still high (over 80%) and the liquid is mostly clear.
R3: Milk – The cob is much larger than before. The starch content in the kernels is accruing quickly, which turns the liquid a whitish color.
R4: Dough – The kernels deepen in color and take on a reddish hue. The liquid in the kernels is now thicker.
R5: Dent – A dent forms on the corn kernels. The moisture content has decreased to about 50% at the beginning of R5, and the insides of the kernels harden considerably.
The development of the various growth stages in corn is very closely tied to something called Growing Degree Days (GDDs). GDDs are a way to accurately track and predict crop development mathematically based on daily temperatures. However, we’ll save the details on how to calculate GDDs for another post.
Each corn seed product is different, but corn reaches physiological maturity about 130 days (or just over four months) after emergence. How do you know it has reached physiological maturity? If you split a kernel lengthwise, you can see a black layer, technically called an abscission, within the kernel. This black layer indicates that the kernels are no longer affected by nutrient or moisture uptake from the plant; it’s totally done growing. The moisture has reduced to under 40% in the kernels, and once the grain has dried sufficiently, it will be ready for harvest.
When many of you come to visit the farm this fall, the corn will probably be in the R3 or R4 stage of growth. If you’re around a field of corn anytime soon, see if you can determine what stage of growth the plants are in and how they’re developing.
I hope you’re all having a safe and enjoyable summer!
Troy is formerly a high school Agriculture teacher and FFA advisor who is passionate about teaching Agronomics, Ag Science, and Plant Biology. Now the manager of the Monmouth Learning Center, Troy has led the Fantasy Farming Challenge for the past three years, helping hundreds of high school students to understand the choices farmers make against the challenges of weather, disease, weed management, and insect pressure.