Submitted by John Toft
CCA, Tekamah, Nebraska

Yesterday, I blogged about the importance of determining the causes behind uneven corn stands in the field.  Things to consider included: planting conditions at the start of the season, possible excessive planter speed over rough soil or residue, planting in unfit soils, shallow or excessive planting depth, failure to close the furrow or worn planter parts.  I also provided a link to help make planter adjustments that promote those “picket fence” stands in your field.

But what if everything I mentioned in yesterday’s post was done properly and you still end up with uneven corn?  Dig up those poorly performing plants!  Nearly all unevenness results from a problem under the soil surface.  Some potential culprits to check for include:

• Insect damage by pests such as wireworms, seed corn maggots, white grubs, sod webworms and black cutworms.
• Seedling diseases and/or rotted kernels.
• Fertilizer injury, including Anhydrous ammonia or the subsequent nitrate salt formed in the ammonia injection band.  This injury can be eliminated by applying ammonia in good soil conditions and not planting directly into the ammonia injection band.
• Varying amounts of residue cover in a field, which can affect soil temperature and soil moisture.
• Cooler soil temperatures not only affect plant growth but also microbial activity responsible for nitrogen and/or sulfur mineralization and the micorrhizal fungal activity instrumental in phosphorous acquisition from the soil. It’s not uncommon to observe soil temperature under varying amounts of residue differing by as much as 10 to 12 degrees Fahrenheit into June.
• Soil Compaction.
• Patchy weed growth left to compete too long within a field often results in uneven corn.

Submitted by John Toft
CCA, Tekamah, Nebraska

It’s important to examine the cause of uneven corn to avoid the situation in the future, if possible.  Some common reasons for uneven corn may be a result of: the planting trip; varying planting depths due to excessive planter speed over rough soil or residue; planting in soils that are too wet; shallow planting depth; excessive planting depth; failure to close the furrow; or worn planter parts.

To help provide “picket fence stands,” make planting and planter adjustments.  It’s important to match the planter speed to field conditions and to avoid planting seeds in extremely poor soil conditions.

Planting in soils that are too wet can lead to sidewall compaction.  This spring I saw where two sidewalls compacted, causing the plant to come out of the ground in two halves.  The under-developed root systems resulting from the compaction are often confined in a flat plane within the furrow trench.  Planting in too wet of soil, especially with coulters, allows sticky soil to build up on gauge wheels resulting in planting depth differences.

Shallow planting places seed in differing soil moisture levels and can potentially delay emergence dates.  Shallow planting also can lead to a shallow secondary root system.  “Rootless corn” may result, or plant development may be greatly delayed compared to neighboring plants.  Excessive planting depth, especially in challenging environment seasons, can result in uneven emergence, too.  However, I have far greater problems over the years with planting too shallow than I have with planting too deep. 

Failure to close the furrow is usually caused by poor soil conditions, improper closing wheels for field conditions, incorrect down pressure, or planting in sod.  Worn or improperly adjusted planter parts can cause or aggravate all the previously mentioned problems.

Although the 2011 planting season may be over and done, it’s important to monitor crop progress throughout the growing season and take notes.  Avoiding these same mistakes during next year’s planting season can help improve plant stands and lead to healthier, higher yielding plants.

In this week’s crop report Nick Benson, Latham’s regional sales manager in northeast Iowa, reported a 20-25% stand reduction in his area due to imbibitional chilling damage.  The damage resulted in what he called some very confused seedlings that were either emerging incorrectly or not emerging at all. We wanted to provide a little bit more information on just what imbibitional chilling is and how it affects seedlings.

Imbibitional chilling damage is the chilling effect seeds may experience when they imbibe, or absorb, water when soil  temperatures are less than 55° F for an extended period of time. The seedlings may “corkscrew” or not emerge when exposed to these coil soil temperatures (see photo). This may happen also when there are rapid swings in air temperatures, of nearly 30° F.

Nick said he has seen results of imbibitional chilling in corn that had been planted April 28-30. Those growers who saw the 20-25% stand reduction decided not to replant simply due to the lateness of the season – another reminder that farmers are at the liberty of the elements.

If you have any questions about imbititional chilling damage, feel free to comment in the field below.