For most of my life, I have heard this claim anytime it gets dry in June. It seems to be a pervasive belief, repeated across the Midwest from Texas to Minnesota and from Nebraska to Ohio: “If it’s a dry June, the roots will grow deep into the soil looking for water.” Not only is this untrue, but it is scientifically unreasonable. I thought I would take this opportunity to explain what really happens.
Roots Can’t “Look” For Water
The first part of this fallacy is that roots “look” for water in the soil. To say that roots look for water is saying that plants have the ability to think and make logical decisions. Plants can’t think, and they are not capable of reason. However, plants do have the ability to react to the conditions they encounter. Everything a plant does is built into its genetic makeup and is dependent on its environmental conditions.
Healthy Plants Need Healthy Roots
How the belief of needing a dry June for roots to grow deep into the soil came about is anyone’s guess. Not all species need the same amount of water for optimal plant growth, but for the purpose of this discussion, we’ll focus on the major commodity crops. In order for roots to grow well, they must first have three things: un-compacted soil, adequate water, and adequate air. Un-compacted soil allows roots to move freely through the soil, growing and picking up nutrients and water in their path. This also allows water and air to travel through the soil, aiding the roots’ growth. Conversely, compacted soil limits the ability of roots to grow, as it restricts the availability of water and air.
Soil Health: Water & Air
Water and air go together in this scenario. Water falls onto the ground and moves into and through the soil because of gravitational pull. Air follows the water into the soil, providing the roots with a supply of fresh oxygen for root growth. In the case of drought or drier than desired conditions, roots are limited in growth by the amount of water available. The lack of water prohibits the gaseous exchanges, slowing root growth. Too much water does essentially the same thing, prohibiting air from entering the soil and preventing necessary gaseous exchanges from occurring.
So, while it’s true that excess water can impede root growth, it’s not because the roots don’t have to look for water; it’s not as though the roots can get lazy. Roots grow as they do as a result of what the environmental conditions allow. When they aren’t getting air, they aren’t growing because they can’t—not because they won’t.
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