June 1, 2011

What Happens if I Planted Corn Too Thick or Too Thin?

Any agronomist with a few years under their belt is used to having this kind of question come up each spring. The phone call usually starts with, “It didn’t seem like the bag count was coming out right on that field ...” My best first-response is, “Let it come up and take stand counts.” In the western Corn Belt, it isn’t always about optimizing yield or standability; it can be about evaluating whether the available soil and water will support that stand density in the field. When the population is too high, there are some options.

corn seedling rows 

Occasionally nature intervenes and may partially fix a stand that is too thick, but most times we must develop our own repair solutions. The correct direction depends on how much the target seeding rate was overshot. For stands that are 10% to 20% thicker than intended, we may just add some additional nitrogen and let the corn run its course. You may have heard that rotary hoeing across the rows or at an angle will remove some plants—but I’ve not found this to be very effective.

If the situation involves over-seeding by 30% or more, we may have to consider a do-over. One next-to-last option is to see if any dairies or beef cattle operations might be interested in chopping that field for silage.

With strong corn prices, it is more likely that we will decide to kill the existing stand and plant the field again. A herbicide will need to be selected that kills corn with glyphosate resistance and also has little or no residual activity so we can replant right away. Replanting to a Genuity® SmartStax® hybrid allows the use of glufosinate to eradicate the first seeding if it was only Roundup Ready®.

green corn rows

The flip side of this question—what to do when the planter was set to a lighter rate than intended—has a simpler solution. Most of these situations involve rates 15% to 25% lower than desired. Even the most fixed-eared hybrid has some capacity to take advantage of the extra space, water and nutrients, and some compensation in grain formation will occur. In either case, there is no point beating yourself up about it; as stated earlier, this situation occurs somewhere nearly every spring.

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