Johnston, IA (June 17, 2024) - Stunted, yellowing corn plants along field edges have been attributed to herbicide drift, insect feeding and soil compaction over the years, but research suggests it’s something called edge effect.

Edge effect is commonly caused by corn microclimate and weather patterns. When air initially meets the corn field, it is dryer at the field edge. Due to plant respiration, the air collects more moisture as it passes further into the field. Thus, corn respiration rates are higher along field edges and, over time, that increase leads to elevated drought stress.

This effect is most pronounced when soybeans, hay or pasture are located adjacent to the corn field. Additionally, the effect is seen more on the southern or western sides of the field.

“Competition for water resources between corn plants, neighboring field crops or grass from the ditch can be the main cause of edge effect,” explains Matt Montgomery, Pioneer Field Agronomist. “This issue is only intensified during bouts of high wind and dryness.”

Higher temperatures naturally increase crop water demand by creating a higher vapor pressure deficit (VPD) between the saturated leaf interior and the ambient air. Corn plants respond to higher VPD by closing their stomata and preserving water. However, this reduces the rate at which plants take in CO2, lowering the rate of photosynthesis and potentially hurting yield.

Greater evaporative demand also increases soil water supply depletion, which can cause longer-term stress on the crop. Plants on field edges may also be at greater risk for sunscald, which occurs when evaporative demand increases faster than the plant is able to respond, causing leaf tissue to die.

“The environment we run into day in and day out is dynamic,” said Montgomery. “Understanding that plants are constantly competing for many of the same nutrients and moisture helps explain yellowing corn and edge effect.”

While the yield impact of edge effect is often minimal, drought stressed corn – especially during grain fill – can lead to yield loss.