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Determine What Sets Corn Plants Back

Determine What Sets Corn Plants Back
More than one factor can limit corn growth.

What do you notice about the plant pictured below? If you count the number of exposed leaf collars, it may not be much behind the taller corn. The plant may be more mature than height would indicate, just because it's growing slowly and the internodes haven't elongated properly.

Three strikes: This small plant recovered somewhat but the plot it was in didn't yield well. Too much went wrong early on, including too much rain, too many weeds, and too little access to nitrogen.

Are there any other symptoms? Sure, the corn has a yellowish tint on some of the leaves, with almost brown tissue at the tip on some leaves. That likely signifies a lack of nitrogen. What you don't know is: 1) if too little was applied, 2) the soil was saturated and the nitrogen disappeared, 3) the soil was saturated and it hadn't been sidedressed yet or 4) saturated soil prevented proper uptake. This plant was from a real plot at the Purdue University Throckmorton Research Center. It was in a trial conducted for Indiana Prairie Farmer and Precision Planting with help from Jeff Phillips, Tippecanoe County Extension ag educator.

"Several things were going on in one of four replications of the experiment," he notes. "You also need to know that no herbicide was soil-applied in conventional tillage, weeds were controlled with post-emergence products. Since it turned wet, the application couldn't be made as soon as it should have been. Weeds were growing between the rows in this part of the field, primarily grass."

So there were three strikes against this plant – grassy weeds not controlled in time, saturated soils, and either lost nitrogen or the inability to take up enough nitrogen. The result was stunted plants that showed signs of nitrogen deficiency, even though the rest of the replications where the soil wasn't as wet and water didn't stand were fine.

The hardest-hit plots in this replication didn't yield as well, and it had nothing to do with the practices being compared: planting speed, planting depth and downforce on planter units. It had everything to do with allowing grass to compete with the corn too long and not getting enough nitrogen to the plants early in the season when important decisions were made about the number of rows of kernels around the ear and length of the ear.

If you find plants like these in your field, can you do anything about it? Dry weather will help return the rooting zone to healthier conditions. The weeds should be sprayed as soon as soil conditions allow. And you should assess whether adding more nitrogen as sidedress would help yield.

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