Corn growth stages start with vegetative, end with reproductive
May 2, 2020
It is really a miracle of nature that a puny, little seedling can grow into a big, tall corn plant within a couple of months. By understanding what happens as a young corn plant develops, growers can help corn become productive adult plants.
Corn seed absorbs water until it is approximately 30-35 percent moisture and then it begins to grow. After planting, a corn seedling will emerge in approximately 100-120 growing degree days. When seedlings emerge as coleoptile, the spear-like leaf, piercing thru the ground, it is called the “VE” stage (vegetative emergence). Roots are very small and the availability of fertilizer close to the roots at this stage is very helpful in stimulating early growth
The number of leaves completely developed with visible collars determines the vegetative stage of a plant. The “V1” is full development of the first leaf.
About two weeks after emergence, the third leaf starts to develop, or the plant reaches “V3”. Seedling roots stop at this stage and the secondary roots known as nodal roots start growing. These become a part of the permanent root system of the plant.
At V3-V4 stage, make sure that weeds are under control. Apply post-emergence herbicides, if necessary, as even small weeds can affect yield. The growing point stays below ground for three to four weeks and is protected from frost or insects on the surface. Freeze at this stage may hurt the leaves but growing point is not destroyed since it is below ground. Don’t cultivate too close to the plant after this stage because the roots may be damaged. Don’t start thinking about replanting at this stage. The nodal roots are growing fast and start taking over the responsibility of gathering water and nutrients for the whole plant. Root hairs also start growing at this stage.
Generally, the first node above ground is the fifth node (V5). Even at this early stage, leaf and ear shoots are starting to develop.
At seedling emergence, young plants face many hurdles such as nutrient deficiencies, seedling diseases like Pythium and Stewart’s bacterial blight, slugs and insects like black cutworms. Corn rootworm beetle larvae attack the roots during June and early July. In a wet spring, watch for for slimy little creatures like slugs — they appear harmless but can cause considerable damage, especially, in low-lying areas of the fields.
Kernel row determination begins in stage V7 of corn. Be sure to side-dress with nitrogen before the plants are too tall, if an additional nitrogen application is desired. Check for deficiency of nutrients like sulfur as well as zinc, magnesium and other micronutrients
In V9, brace roots appear on the soil surface to serve as a plant anchor and help obtain water and nutrients. A corn plant is approximately 30 to 36 inches tall.
In the V12 corn stage, kernel row determination is nearly complete.
In the VT stage (vegetative tassel), the plant is at or near maximum height, all leaves are visible, the tassel is extended but silks are not yet visible.
After a corn plant completes vegetative states, it transitions to reproductive states to form kernels and ears. During the first reproductive stage, R1, every potential kernel (ovule) develops its own silk, visible outside the husks. Silks capture pollen the tassel sheds and move it down to the ovule, where pollination occurs. At peak pollen production an individual plant can release 500,000 or more pollen grains per day. Pollen shed occurs for seven or more days in most corn fields.
About 10 days after R1, R2 begins with “blisters” (developing kernels) appearing on the cob. In R2, kernel moisture is approximately 85% and silks begin to dry and darken.
In the R3 stage, kernels contain a milky-white fluid, caused by accumulating starch, moisture content is around 80 percent.
In R4, around 25 days after R1, accumulated starch begins to thicken to a doughy consistency; moisture is approximately 70 percent.
Starch accumulation in corn increases kernel dry matter. In R5, kernels are dented and dry matter accumulation is approximately 45 percent.
About 33 days after R5, a kernel reaches physiological maturity, or R6. In R6, corn is roughly 32% moisture and a black layer forms at the kernel tip preventing further accumulation of dry matter.
Starch is the primary source of a kernel’s dry weight and is the most widely used part. It is the key component in fuel, sweeteners, bioplastics and more.
Learn more about corn growth stages