Did your corn shift into survival mode?

Think of each corn plant as a factory. There are five times during the season when that plant makes internal decisions about how many viable kernels it can produce. Which decision each plant makes depends upon whether it’s in luxury mode, optimum mode or survival mode.

Did your corn shift into survival mode?

Think of each corn plant as a factory. There are five times during the season when that plant makes internal decisions about how many viable kernels it can produce. Which decision each plant makes depends upon whether it’s in luxury mode, optimum mode or survival mode.

It’s been a tale of many seasons wrapped into one, starting with corn planted in two shifts. It’s also been a season of plentiful moisture early, then very little moisture late for some. The only constant has been warm temperatures, becoming very hot after pollination.

Key Points

• There are five key stages when corn adjusts yield during the season.

• Corn has three modes — luxury, optimal and survival.

• Conditions change on the go during the growing season.


To determine what you may have already found in your cornfield, or what you will find, review these things. First, what was the “macroclimate” at each critical stage? Macroclimate refers to planting date, rainfall amount and timing, degree of sunshine, and other whole-field factors. Micro-environment refers to what the individual plant experienced. Was it near a fencerow? If so, it may have thought things were good and put on two ears. If it was inside the field, the signals may have been different.

Five stages

Here are the five yield points for corn in a season:

One. How much competition is there around each plant at seedling stage? If there’s competition, the plant likely will develop one ear.

Two. Waist-high corn is ready to determine how many rows of kernels per ear. It’s related to genetics, but it’s influenced by environment as well.

Three. Individual plants can increase the number of kernels at the ear tip at pollination if all signals are go. More often than not, they weren’t. Expect to find aborted kernels at ear tips.

Four. Depth of kernels is determined during the grain-fill period. If gray leaf spot was rampant, the plant may have pulled back on kernel size.

Five. Test weight is somewhat determined in August. If the signal was warm and dry, test weight could be lower. Test weight is also tied to genetics.

Operating modes

Imagine each plant has tiny cells inside running the factory. There’s a big gauge with three choices: luxury, optimal and survival. The controller, much like the engineer on a train, moves the dial to one of the three.

In luxury mode, the environment is better than normal, and plants go into overdrive. At the optimal setting, environmental conditions are normal, and there’s an absence of stress. If there’s stress, the controller turns the dial to survival mode. Here’s where kernel tips abort.

Plants may also cannibalize lower leaves and stalks to find enough nutrients to finish the kernels. Some cornfields were in survival mode late in the season.

Firing that looks like nitrogen deficiency can be caused by stress. This showed up on many fields this year when conditions went from optimal or even luxury mode to survival mode over a few short weeks.

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Switching modes: When corn plants sensed drier, hot conditions, many changed from optimal to survival mode. A simple pinch or push test may let you know if stalks are compromised.

This article published in the October, 2010 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.

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