A new poster titled “Corn Growth and Development” has just been published by K-State Research and Extension. The poster can be seen at: http://www.bookstore.ksre.ksu.edu/pubs/MF3305.pdf
The poster lists the primary growth and development stages of corn, with illustrations of each stage. It describes the growth stage, and discusses some of the significant management considerations of each stage.
Authors of the poster include Ignacio Ciampitti, K-State Crop Production and Cropping Systems Specialist; Roger Elmore, Cropping Systems Agronomist, University of Nebraska-Lincoln; and Joe Lauer, Corn Specialist, University of Wisconsin. Supporters of the poster include the Kansas Corn Commission, National Corn Growers Association, K-State Research and Extension, University of Wisconsin, and University of Nebraska-Lincoln.
The following excerpts are from the poster, focusing on the growth stages occurring in Kansas corn fields at this time of the year.
V6 – Sixth-Leaf
Six leaves with collar visible. The first leaf with the rounded tip is senescent; consider this point when counting leaves. The growing point emerges above the soil surface. All plant parts are initiated. Sometime between V6 and V10, the potential number of rows (ear girth) is determined. Potential row number is affected by genetics and environment and is reduced by stress conditions. The plant increases in height due to stalk elongation; nodal roots are established in the lowest, below-ground nodes of the plant.
Scout for weeds, insects, and diseases. Rapid nutrient uptake begins at this stage. Timing nutrient applications to match this uptake enhances the potential for greater nutrient use efficiency, particularly for mobile nutrients such as nitrogen.
V10 – Tenth-Leaf
Brace roots begin to develop in the lower above-ground nodes of the plants. Until this stage, rate of leaf development is approximately 2 to 3 days per leaf.
Nutrient (potassium = K > nitrogen = N > phosphorous = P) and water (0.25 inch per day) demands for the crop are high. Heat, drought, and nutrient deficiencies will affect potential number of kernels and ear size. Scout for root lodging issues and diseases (e.g., common rust, brown spot). Weed control is critical since corn does not tolerate early-season competition for water, nutrients, and radiation well.
V14 – Fourteen-Leaf
Rapid growth. This stage occurs approximately two weeks before flowering. Highly sensitive to heat and drought stress. Four to six extra leaves will expand from this stage until VT.
Scout for root lodging issues, greensnap (likely to occur from V10 to VT) and diseases (e.g., common rust, brown spot). Abnormal corn ears can occur and be obvious from this time until flowering.
VT – Tassel
Potential kernels per row is set, final potential grain number (number of ovules), and potential ear size are being determined. Last branch of the tassel is visible at the top of the plant. Silks may or may not have emerged. The plant is almost at its maximum height.
Nutrient (K > N > P) and water (0.30 inch per day) demands for the crop are close to maximum. Heat and drought will affect potential number of kernels. Scout for insects (e.g., corn leaf aphid, western bean cutworm, corn earworm, fall armyworm) and diseases (e.g., gray leaf spot, southern rust, northern leaf blight). Total leaf defoliation severely affects final yields.
R1 – Silking
Flowering begins when a silk is visible outside the husks. The first silks to emerge from the husk leaves are those attached to potential kernels near the base of the ear. Silks remain active until pollinated. Pollen falls from the tassel to the silks, fertilizing the ovule to produce an embryo. Potential kernel number is determined. Maximum plant height is achieved. Following fertilization, cell division is occurring within the embryo.
Nutrient (N and P accumulation is still progressing, K is almost complete) and water (0.33 inch per day) demands are at the peak. Heat and drought will affect pollination and final grain number. Defoliation by hail or other factors such as insects will produce a large yield loss.
A hard copy of the poster, which is 20 inches wide and 30 inches long, can be ordered from K-State at no charge. There is a limited supply.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist