Pioneer Agronomy Sciences recommends planting corn at a depth of 1.5 to 2 inches for optimal emergence and root development. Studies showed corn planted at 3/4 inches took longer to emerge than corn planted at 2 inches, even in soils prone to crusting. Soil temperature was similar at 3/4 and 2 inch depths early in the season, so warmer soil wasn't responsible for the faster emergence of deeper planted corn. Establishing the nodal root system below the soil line through proper planting depth reduces risks and improves the corn plant's ability to withstand stress.

1. Pioneer Agronomy Sciences
Corn Planting Depth
©2010, Pioneer Hi-Bred

2. How Deep Should Corn Be Planted?
Most university extension publications recommend a corn
seeding depth of about 1.5 to 2 inches, for two important
reasons:
1) To achieve good seed-to-soil contact so corn can absorb about 30%
of its weight in water to germinate
2) To establish a strong nodal root system, growing well below soil line
Shallow planting can cause nodal roots to begin
development at or even above the soil

3. Corn Nodal Root Development
Corn nodal root development normally
starts about ¾” below the soil line
The nodal root system:
Helps structurally support the corn plant
Is responsible for uptake of the vast
majority of the water and nutrients the
plant will need through its lifetime
Establishing a good nodal root system:
Reduces the risk of early season root
lodging Corn early growth and development
Helps the plant fare better under drought
stress

4. Corn Depth Studies
Shallow planted corn does not emerge
sooner
In 2009, Pioneer® brand 35F44 was
planted at approximately 2 inches and ¾
inches deep in a NW Ohio study
The deeper-planted corn emerged first
In fact, the corn planted 2 inches deep
was at stage V1 when the corn planted ¾
inches deep was at VE Planting depth measurements
of Pioneer 35F44

5. Corn Depth Studies
Shallow planting is NOT necessary to
allow the crop to penetrate the crust
that can occur with heavy clay soils
A study was conducted in a once-
swampy region of NW Ohio where
most soils have high clay content and
are poorly drained (a perennial
challenge to corn emergence)
In 2009, in spite of a slight crust on Soil crusting
the soil, the Pioneer 35F44 planted 2
inches deep still came up faster than
the corn planted ¾ inches deep

6. Results and Discussion
Why was there such a difference in speed of emergence?
Soil-seed contact was better and soil moisture was more stable at the
2-inch depth
Soil temperature – shouldn’t the ground be warmer closer to the
surface?
A 2001 study evaluating temperature effects on emergence revealed that
in early April (when soils are cold), soil temperatures were almost the
same at the 0.4-inch and 2-inch depths
From April 15 to 18 that year, the 2-inch depth was actually slightly
warmer than the 0.4-inch depth
Soil temperatures did not deviate until early May when highs reached the
upper 70s to mid 80s F

7. Results and Discussion
Why was there so little difference in temperature between the 0.4-inch
and 2-inch depths early in the season?
Lower sunlight intensity and the “insulating” factor of the 2-inch deep soil
can account for the minimal difference in soil temperatures
It can be true that the soil is warmer at shallower depths, but this differential
doesn’t typically become important until after the corn crop has emerged
Soil Temperatures (Tilled) Soil Temperatures (No-till)
85
85
75
75
Temp (F)
Temp (F)
65 65
55 55
45 0.4" Depth 45 0.4" Depth
2.0" Depth 2.0" Depth
35
35
6
15
22
29
13
5/
6
15
22
29
13
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