Corn roots grow rapidly starting at the 4th-leaf stage and continue throughout vegetative development. This typically occurs from June to early July. Several factors affect root growth, but temperature and soil moisture are the most relevant factors in the absence of soil constraints. Well-developed, deep root systems are essential to support water and nutrient uptake and thus high yield potential. Hot and dry weather results in a depletion of moisture in the top 6-inch soil layer. This occurred in June of 2016 and also during the first two weeks of June 2017. Crop stress was evident in light soils or where root development was restricted. Should you be concerned about this? Maybe, maybe not. It is known that plant roots cannot grow in dry or saturated soil conditions. However, at this time it is unlikely that water is limiting root growth below a 6-inch soil depth.
Iowa State University
Archontoulis, Sotirios and Licht, Mark A., "How Fast and Deep do Corn Roots Grow in Iowa?" (2017). Integrated Crop Management News. 2442.
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