Recognizing Water Stress and Critical Growth Stages in Corn and Soybeans

By Angie Gradiz and Younsuk Dong

When it comes to growing high-yielding crops, timing is everything, especially when it comes to water. Water makes up 80–95% of a plant’s fresh biomass and plays a key role in various physiological processes. Water stress is one of the most limiting factors in crop production, affecting grain yield, quality and nutrient uptake. In Michigan, stress from low soil moisture often occurs during the hottest days from July through mid-August, right when corn and soybean are at their most sensitive growth stages.

Understanding when and how water stress occurs can help you protect your crop investment and make timely and informed management decisions.

What happens during water stress?

Water stress occurs when a plant’s water use exceeds water uptake from the soil, leading to a water deficit in the root zone. In response, plants activate several adaptive mechanisms: roots grow deeper for moisture, leaves may curl to reduce surface area, increase cuticle layer and stomata often close to limit water loss through transpiration.

While stomata closure helps conserve water, it also restricts gas exchange, which can hinder crop growth and development. But the effectiveness of these defenses depends on the crop type, hybrid/variety, planting date, growth stage, and severity and duration of the stress.

Plants generally use two main drought defense strategies, according to Seleiman (2021):

1. Escape – speeding up development and shortening the life cycle through early flowering and maturity.
2. Avoidance/tolerance – reducing transpiration, enhancing root growth, or changing leaf orientation to conserve water.