Rootless corn syndrome or “floppy” corn is when a corn plant’s root system has not grown properly. This root development issue can occur as early as the V2 corn growth stage. When a “floppy” corn plant is dug up, the seminal roots will be visible, but there will be no—or poorly developed—nodal roots.
Corn plants have two root systems that are easily visible early in the year: seminal and nodal. The initial root system is comprised of the radicle and seminal roots. The seminal roots help anchor the young seedling and provide it with nutrients and water before the nodal root system is developed.
Seminal root growth slows after seedling emergence. Although the seminal roots continue to function throughout most of the plant's life, their most important contribution comes before the nodal roots are established. The nodal roots are important in providing the majority of the water and nutrients the corn plant needs for growth and development after V4.
Rootless corn syndrome is the direct result of poor nodal root development that could occur from weather related conditions like very dry topsoil or a combination of the seed furrow reopening and dry seed furrow conditions. If nodal roots do not encounter moisture when developing, the plant’s growth could stall and/or the node set could die.
This can also occur with shallow planted seeds. Nodal root growth is highly sensitive to high temperatures. Once unshaded surface soil temperatures reach the mid 90's or higher, nodal root growth of a shallow corn plant may stop. Plants are forced to rely on the seminal root system or limited nodal root growth until more favorable temperatures and moisture conditions allow nodal root growth to resume.
Plants exhibiting rootless corn symptoms have either lodged and are laying on the ground or are about to lodge. Sometimes, the corn will only be anchored in the soil by a single nodal root or by seminal roots. Before the problem is evident, corn plants may appear vigorous and healthy but can fall over due to limited or no support later. Affected plants lack all or most nodal roots; existing nodal roots may appear stubby, blunt, and not anchored to the soil. Due to a lack of root mass, the affected plants can be expected to wilt, have stunted growth, or eventually die in extreme conditions.
Photos. Rootless corn from Johnson County, IA at approximately V4 growth stage (photo credit Ryan Hahn, 2021).
Rootless corn can recover. After plants have lodged, adequate rainfall will promote nodal root development and many impacted plants recover, yet recovery is severely hampered when conditions remain dry. Moving soil around exposed roots will aid recovery, yet this is extremely difficult if plants are laying on the ground or in a no-till situation. Rain is the best solution as it moistens the seedbed allowing for root establishment and growth.