By Blake Jackson
According to Ashley Isaacson, Extension Educator at Penn State Extension, and Daniela Carrijo, Grain Production Extension Specialist at Penn State Extension, corn yield potential is determined through several critical growth stages, beginning well before pollination and continuing through early grain fill.
Understanding these stages can help growers identify when stress affects yield and recognize its impact on ear development.
The process begins with ear size determination. Between growth stages V5 and V7, corn plants initiate ear shoots and establish the number of kernel rows, a trait largely controlled by genetics. Kernel rows generally remain constant unless the crop experiences severe stress during this brief period.
The number of kernels per row develops over a longer timeframe, typically from V5-V7 through V12-V15, ending about two weeks before silks emerge. Unlike row number, kernel length is highly influenced by environmental conditions.
Stress from drought, nutrient deficiencies, or other factors during this stage can reduce the number of ovules, ultimately shortening ear length and reducing yield potential.
Pollination occurs during the R1 silking stage, when pollen must successfully reach receptive silks. Each silk corresponds to a potential kernel. Poor synchronization between pollen shed and silk emergence can result in kernels failing to develop.
Drought stress is especially problematic because it often slows silk growth while accelerating pollen shed, increasing the likelihood of pollination failure.
Following pollination, kernel development continues through the early grain-fill stages. During this period, successfully pollinated kernels may still be lost through kernel abortion if the plant lacks adequate energy due to stress. Heat, drought, cloudy weather, disease, hail damage, nutrient shortages, and excessive plant populations can all reduce photosynthesis and limit kernel survival.
One common symptom of stress is tip dieback, also called tip-back, where kernels fail to develop near the tip of the ear. This can result from poor pollination or kernel abortion. Another symptom is zipper ears, characterized by incomplete or missing kernel rows, often associated with severe drought during early grain fill.
Because drought can affect ear size determination, pollination, and kernel retention, it remains one of the most significant threats to corn yield.
Growers investigating yield losses should examine ears across the field and compare symptoms with weather conditions during three key periods: V5-V15, when ear size is established; VT-R1, when pollination occurs; and R1-R3, when kernels are retained during early grain fill.
By understanding these developmental stages, producers can better diagnose yield-limiting factors and evaluate how seasonal conditions influenced crop performance.
Photo Credit: gettyimages-chrisboswell
Categories: Pennsylvania, Crops, Corn