Flint on Crops: Get Ready to Plant Corn – Commentary

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Farmers will begin planting corn as early as 30 days from now. Corn planting will last around 4 to 5 weeks. Of course there will be corn planted outside that block of time, but for the sake of discussion let’s say that we will shoot for planting our corn crop between March 15 and March 30.

We like to plant corn as early as possible for several reasons, the main one of which is water. Corn plants that emerge around the end of March or the first days of April can normally reach the reproductive “silk and tassel” stage before supplies of soil moisture are depleted. This is most critical for farms without irrigation, but it saves a lot of expense for those who have irrigation as well.

Another big item supporting the early planting of corn is the avoidance of problems. On the issue of weeds, the fields should preferably be free of weeds when corn plants emerge so that there is no competition. This is the reason we apply burndown and residual herbicides and avoid spring tillage that brings more weed seed to the surface.

A winter weed that has special significance for corn is herbicide resistant ryegrass. This plant not only can compete with corn as other weeds do but it is also “allelopathic” to corn in that it can compete biochemically as well. Ryegrass cannot be tolerated in corn fields since it can cause huge yield loss if the density of the weed is significant.

There are only two “good” ways to get rid of ryegrass. Tillage is not good in spring since it can cause problems for supporting the equipment required for planting corn. The other is the application of herbicide mixtures containing clethodim.

This herbicide will not only control ryegrass and other winter grasses but it will also damage corn if the corn seeds are planted and emerge while the clethodim is active. This herbicide should be applied around five weeks before planting to allow it to dissipate sufficiently to prevent damage to corn.

Other issues include the use of seed treated with an insecticide to prevent or reduce injury from insects, mainly the sugarcane beetle. Seed should also be treated with fungicides to protect the germinating seed from rotting organisms and fungi that destroy the young seedlings.

In nonirrigated fields the planter should be set to deliver a seed about every 6 inches in 38 inch rows for a seeding rate of 27,500 per acre. A similar seeding rate can be achieved in 30 inch rows with a seed every 7.5 inches. Seeding depth should be at least two inches in order for seminal roots to develop under the soil surface on the growing plant.

This is critical for moisture uptake and to avoid lodging. In irrigated fields the seeding rate may be increased somewhat, but without irrigation this population has been shown consistently dependable for most varieties. Seed should be spaced as evenly as possible to avoid competition among the plants.

I have not mentioned setup of planters which is critical for correct seed placement, but a comment is that when the seed are placed the slit must be closed well for even emergence and to avoid the problem we call “rootless corn syndrome”.

Avoid air pockets in the slit since seed in these pockets may deteriorate before they can emerge. Every field situation is unique, varying with soil type and moisture content. Planting into wet soil is usually a mistake.

My suggestion is that soil temperature should be above 65 at a 2 inch depth, with a good forecast. The critical time is during water absorption and germination. If seed absorb cold water you may be in for problems. Call if we can help with any of this.

Thanks for your time.


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