Visual Guide To Corn Growth Stages

Growth stage R1 occurs when silks are first visible outside of the husks. Moisture stress during this stage causes poor pollination, reducing seed set and yield.

Identifying corn growth stages is essential for successful management of pests, irrigation and fertility as strategies for achieving and protecting yield are often based on these stages. Conversely, when problems arise, the growth stage it occurs in offers the most effective way to tell how most yield will be lost. For example, the effects of frost, moisture stress, plant diseases or insect injury on yield will be determined by the growth stage in which these events occur.

To help identify the growth stages of corn, Clemson University’s Michael Plumblee, corn and soybean Extension specialist, along with Bennett Harrelson and Sarah Holladay, both graduate research assistants with the plant and environmental sciences department, collaborated on a visual guide. The guide will help growers, consultants, Extension and research personnel properly identify corn growth stages in field corn hybrids.

The rate at which corn grows and develops changes during the season. Young corn plants grow slowly, but as more leaves are formed, the rate of growth increases. Under normal growing conditions, the rate of plant development is largely dependent on temperature. Environmental factors, such as water and nutrient deficiencies, can alter the relationship between plant growth and temperature. If water, nitrogen or other resources become limiting, especially when the plant is rapidly growing, yield is often reduced. Disease and insect infestations can interfere with water and nutrient uptake or severely damage the plant to the point of yield loss. Weeds are direct competition for water, nutrients and light.

Emergence To Black Layer

Generally, corn growth and development can be divided into vegetative and reproductive growth stages. The beginning of each stage starts when at least 50% of plants in the area are at that stage. The vegetative growth stage begins with corn emergence and is completed by tasseling. The reproductive growth stages start with silking and end when a black layer forms, indicating physiological maturity.

Being able to visually identify the stage of growth will allow for knowing when the corn plant is most at risk. The growth rate increases with the presence of each new leaf, and under non-stressful conditions, the time between new leaves will decrease as the season progresses. The plant is most vulnerable to stress during silking when
important pollination processes occur.

As the reproductive stages progress, the effect of stress on seed weight will decrease, while the effect on seed number will be minimal after R2. According to research data, the highest yields are achieved in areas where environmental conditions are favorable for these growth stages, especially R1. Unfavorable conditions early in the season will limit leaf size, which will decrease photosynthesis, while stress later in the season can affect pollination in the form of kernel size and number.

The Visual Guide To Corn Growth Stages can be found on the Clemson Cooperative Extension Land Grant Press website at https://lgpress.clemson.edu/publication/visual-guide-to-corn-growth-stages. CS

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