IF CORN PLANTING IS DELAYED BY TWO WEEKS, WILL THE CROP BE TWO WEEKS LATER IN REACHING MATURITY?

No. As planting date is delayed, the number of days to a specific growth stage decreases because growing degree units per day are increasing as it gets later. A 1996 study by Louisiana State University showed that Pioneer 3167 planted March 14 reached black layer just 2 days later than when it was planted February 28.

GROWING DEGREE UNITS

Growing degree units (GDUs) are a means of tracking corn plant development. Corn growth and development are driven by heat. GDUs are a measure of accumulated heat units. Different crops have different critical temperatures that determine when growth and development occurs. The low temperature for corn is 50 degrees F and the high temperature is 86 degrees. GDUs for corn are calculated as follows:

GDUs = [(daily low + daily high)/2] - 50

If the daily low is below 50 degrees, use 50 and if the daily high is above 86, use 86. Corn development almost stops below 50 degrees and slows above 86 F.

YES, YOU CAN PLANT CORN TOO SHALLOW, JUST AS YOU CAN PLANT CORN TOO DEEP

Corn has a two-part root system. Seminal roots are the initial root system and grow from the seed. They support the plant for about three weeks after germination. Then the primary root system known as the nodal roots take full control. Nodal roots originate above the seed. When corn is planted too shallow, nodal roots develop near the soil surface or on top of the soil instead of the normal below ground position. Please don’t confuse nodal roots with brace roots! Nodal roots look just like brace roots but should develop in the ground, while brace roots develop 2 to 3 inches above ground and appear just prior to tassel. Recent studies show corn yields were highest when corn was planted 1.5 - 2 inches deep but no deeper than 2 inches!

WHAT ARE THE CONSEQUENCES OF PLANTING CORN TOO SHALLOW?

1) POOR ANCHORING SYSTEM - Above ground nodal roots increase the risk of lodging from wind. If this condition is discovered early in the season, cultivation will eliminate the problem by covering the nodal roots
with soil.

2) POOR WATER AND NUTRIENT UPTAKE - Above ground nodal roots will restrict water and nutrient uptake. During dry spells, fields with above ground nodal roots suffer from unnecessary water stress and nutrient deficiencies.

THE FALLACY OF SELECTING CORN HYBRIDS BASED ON SINGLE PLOT DATA

Yield data from an individual plot is interesting to read, but don’t bank on a single plot from last year to reliably predict the best hybrid for this year. Be sure to look at plot data from several locations and/or years as this will improve the selection process and also pinpoint the diversity of a select hybrid under varying environments.