Today managing your corn crop requires knowledge of the different growth stages of the corn plant. Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications. Each week throughout the growing season I will discuss the various corn growth stages and management issue at each stage.
V5 – V6 – 350 – 400 Growing Degree Days (GDD’s)
Source: Corn Growth and Development, Iowa State University
OK, now stuff is really happening!
Plants with their first six leaves collared are defined as V6. The lower leaves are more weathered and become increasingly harder to identify and count as they tear away from the expanding stalk and decompose. All leaves are initiated byV6 although many are too small to see without magnification. Each leaf originates from a stalk node with internode tissue separating the nodes. A minor amount of internode elongation began prior to V6 with the majority occurring from this point forward
The growing point has now transitioned from below to above the soil surface due to internode elongation. The nodal root system is dominant now with the root mass approximately one third of the plant’s total biomass.
Ear shoots, one of which will develop into a harvestable ear, are being initiated and growing along the stalk at various nodes. Ear shoots are first present at lower stalk nodes as these are initiated first with upper ear shoots following
Although the primary ear shoot is not yet visible, it is initiated at approximately V6 magnification will be necessary to see it. The primary ear is typically located at nodes 12, 13, or 14. The potential size of an ear is a function of the number of kernel rows around the ear and the number of kernels per row. The row number will be even (versus odd) because initial rows divide laterally, forming two rows each. Row number is determined shortly after the ear is initiated, approximately V7. Most hybrids grown commercially have 16 or 18 kernel rows per ear. The row number is strongly related to a hybrid’s genetics and impacted only by serious environmental factors such as drought, nutrient deficiencies, and improper herbicide applications.
The tassel is initiated at approximately V6, although it will not be visible without magnification. It is identifiable with plant dissection by V7.
Management/Scouting: Scout for root rots, seedling blight, cutworms, slugs, billbugs, Herbicide injury, flooding, weed escapes and excess weed competition.