Corn (maize) has a high demand for water, making consistent moisture availability the most important variable in determining final grain yield. This high requirement stems from the plant’s massive leaf area, which constantly loses water through transpiration during photosynthesis. Water needs fluctuate dramatically throughout the growing season based on the plant’s developmental stage and environmental conditions. Successful corn production relies on meeting these changing demands, especially when the plant is most sensitive to moisture deficits.
Total Seasonal Water Consumption
A corn crop requires 20 to 35 inches of water over an entire growing season, supplied by rainfall and irrigation. This seasonal total represents water lost through evapotranspiration, which includes evaporation from the soil and transpiration from the leaves. The exact figure varies significantly depending on local climate conditions, such as temperature, humidity, and wind speed. A corn hybrid with a longer maturity period requires more total water because it is actively growing and transpiring for a greater number of days.
Critical Needs During Key Growth Stages
A corn plant’s water needs change dramatically as it develops, starting with the lowest demand at planting and emergence. During this initial stage, the plant relies on existing soil moisture and early rainfall for germination and seedling establishment. As the plant enters the vegetative growth phase, characterized by rapid stalk and leaf development, its daily water consumption steadily increases. This phase builds the necessary infrastructure to support the later, high-demand reproductive stage.
The period surrounding tasseling, silking, and early kernel filling is when the plant reaches its peak water requirement and is most vulnerable to drought. During this reproductive phase, corn can consume between 0.25 and 0.35 inches of water per day, potentially climbing to 0.50 inches during hot, dry, and windy conditions. Approximately half of the plant’s total seasonal water use occurs during this intense reproductive window. A lack of water during silking is particularly devastating because it can lead to pollination failure, potentially reducing harvest yield by up to 50%.
The high demand continues through the blister and milk stages as the kernels rapidly accumulate starch and moisture. Once the grain enters the maturation phase, progressing through the dough and dent stages, the daily water requirement begins to decrease. Water is still necessary during grain fill to ensure kernels reach their full size and weight. This must occur before physiological maturity, which is known as the black layer stage.
Recognizing Signs of Water Stress
When natural rainfall is insufficient to meet the plant’s high daily water requirement, the corn plant exhibits visible defense mechanisms to conserve moisture. The most common sign is leaf rolling, where leaves curl inward to reduce the surface area exposed to the sun, decreasing water loss through transpiration. If leaves roll only during the hottest part of the day (late morning to mid-afternoon) and flatten out by evening, the plant is experiencing moderate, temporary stress.
Leaf rolling that begins in the early morning and persists throughout the day indicates severe, sustained drought stress. Prolonged and intense water deficits also cause a noticeable change in the plant’s color. The normally vibrant green leaves shift to a darker, dull bluish-gray hue as the plant struggles to maintain turgor pressure. If the stress continues, the leaves will eventually turn completely gray, signaling the death of the leaf tissue.
Supplementing Rainfall: Basic Irrigation Methods
When natural precipitation is insufficient, particularly during the reproductive stage, supplemental irrigation becomes necessary. The goal of any irrigation method is to deliver water efficiently to the root zone, preventing stress and yield loss. Center pivot systems are a common form of overhead sprinkler irrigation, using a rotating lateral pipe to apply water over a large circular area with an efficiency that can reach 75 to 85%.
Another approach is furrow or flood irrigation, a traditional method that runs water down channels between the rows. While this method has a lower initial cost, its efficiency is the lowest, often ranging from 40 to 60% due to runoff and evaporation. The most water-efficient method is drip irrigation, especially subsurface drip irrigation (SDI). SDI uses tubes buried near the root zone to deliver water directly to the plant, minimizing evaporation and achieving efficiencies of 95% or higher.