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Key Points
- Rootless corn occurs when unfavorable soil conditions around the crown of the plant prevent nodal roots from developing normally.
- Rootless corn often becomes apparent between the V3 and V8 growth stages when plants fall over due to their underdeveloped root systems.
- Typically, the best solution to rootless corn is a soaking rain that provides enough moisture around the crown of the plant to sustain the development of new nodal roots
- What is Rootless Corn Syndrome?
- Corn Root Development
- Contributing Factors
- Management Options
What is Rootless Corn Syndrome?
- Rootless corn syndrome, also referred to as floppy corn, occurs when the nodal root system fails to develop properly, which can cause plants to fall over (Figure 1).
- Affected plants can have few nodal roots or none at all, in which case they will only have the mesocotyl and seminal root system holding them to the ground.
- Rootless corn most commonly becomes apparent between the V3 and V8 growth stages. Affected plants will often appear healthy and vigorous at first but eventually fall over when the underdeveloped root system is no longer able to anchor the growing plant.
- Plants that remain unable to initiate nodal root development may wilt and eventually die.
Figure 1. Rootless corn syndrome caused by shallow planting followed by dry soil conditions.
Corn Root Development
- A corn plant produces two root systems – the seminal root system and the nodal root system (Figure 2).
- The seminal root system is comprised of the radicle and up to three pairs of lateral seminal roots. The seminal roots originate from within the seed embryo and sustain the corn seedling for the first couple of weeks after emergence.
- The nodal roots are the main root system that sustains the plant through the growing season. Nodal roots develop sequentially from individual nodes above the mesocotyl.
- The nodal roots begin development at the junction of the mesocotyl and coleoptile, which is normally ¾ inch below the soil surface for corn planted at adequate depth.
- Roots from the first five stem nodes typically emerge below ground with the first four packed tightly together and the first noticeable internode between nodes four and five.
Figure 2. Left: V1 corn plant prior to nodal root development with only seminal roots. Right: V2 corn plant with nodal roots beginning to develop above the seed.
Contributing Factors
- Rootless corn occurs when unfavorable soil conditions around the crown of the plant prevent nodal roots from developing normally. There are a number of factors that can contribute to poor nodal root development:
- Extremely Dry Soil – Prolonged hot and dry weather early in the season can dry out the soil near the surface, particularly in fields with minimal surface residue.
- Nodal roots emerging into extremely dry soil can desiccate and die if they are unable to reach soil moisture. Affected roots will appear shriveled and discolored (Figure 3).
Figure 3. A corn plant showing rootless corn syndrome that has been dug up showing the seed, mesocotyl, and seminal roots.
Figure 4. A corn plant exhibiting rootless corn syndrome. The mesocotyl is visible anchoring the plant to the ground but nodal roots have failed to develop.
- Shallow Planting – Planting too shallow causes nodal root initiation to occur closer to the soil surface than at the usual ¾ inch depth, which increases the risk of nodal root initiation into hot and dry soil. Corn should never be planted less than 1½ inches deep.
- Heavy Rain After Planting – Excessive rainfall after planting can cause subsidence of the soil around the furrow or erosion that removes soil from around the crown of the plant, both of which can increase the risk of poor nodal root development.
- Compacted Soil – Compacted soil around the seed can create a physical barrier to root elongation and inhibit nodal root development. This can result from sidewall compaction caused by planting into wet soil.
- Exposed Crown – Seed furrows that are not adequately closed or that reopen as soil dries after planting can expose the crowns of developing plants and cause newly initiated roots to desiccate. Loose and/or cloddy soil around the seedling can have the same effect (Figure 5).
Figure 5. Corn plants in field that had severe rootless corn syndrome showing up in many plants. The planter furrow opened back up due to extremely hot and dry conditions following planting. Depth gauge shows that the depth of the “crack” is 2.5 inches - clear down to the depth of the seed.
Management Options
- There is little that can be done to remedy rootless corn once it has occurred.
- In some cases, interrow cultivation may help enable nodal root development by throwing soil around the base of the plants, but this may not be helpful if the soil is already extremely dry and can be difficult to do without burying plants that have already flopped over.
- Typically, the best solution to rootless corn is a soaking rain that provides enough moisture around the crown of the plant to sustain the development of new nodal roots (Figure 6).
Figure 6. Corn plants that experienced rootless corn syndrome. The plant on the left was able to recover and successfully developed new nodal roots following a rainfall, while the plant on the right was not able to recover.
The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary. Pioneer® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.