ALABAMA COOPERATIVE EXTENSION SERVICE I AUBURN UNIVERSITY, ALABAMA 36849-5612
Alabama Production Guide For Non-Irrigated Corn
Paul L. Mask, Agronomist-Grain Crops
Charles C. Mitchell, Jr., Agronomist-Soils
Corn is one of Alabama's most important grain
crops. Alabama farmers usually harvest more than
half a million acres of corn each year.
In 1986, Alabama farmers produced a state
average corn yield of 56 bushels per acre. This was
considerably below the national average of 119
bushels per acre. Several factors contribute to
Alabama's low com yields. Insufficient moisture and
high temperatures at silking and tasseling are frequent problems. Even with the best management
techniques, uncontrollable weather conditions can
cause yield reductions. Fortunately, many factors
which determine high yields can be controlled.
Soil Testing
Soil testing to determine lime and fertilizer requirements is basic for good com yields. Fall sampling is best since it allows plenty of time to do any
needed liming and fertilizing. Thke samples from the
full depth of the plow layer.
In areas that are routinely tested, one soil test
can represent 20 acres or more as long as the entire area is similar with regard to soil type, drainage,
and past treatment. In areas which have not been
tested recently, take one soil sample from about
every 10 acres.
will depend on the fertility status of the soil as indicated by soil testing. A shortage of either potassium
or phosphorus can limit yields. Current Auburn
University recommendations call for 40 pounds per
acre of both phosphate and potash on soils testing
medium for both nutrients and 60 pounds per acre
on soils testing low for both nutrients.
Nitrogen. Fertilization with adequate levels of
nitrogen is required for good com grain production
on all Alabama soils. The cost of nitrogen is the
largest single variable cost in com production.
Carefully consider the rates used and the method
of application for each management system. No
other element produces such large and consistent
increases in com yields. For economical returns,
larger quantities of nitrogen are normally required
than are needed of any other element.
\
Fertilization And Liming
Lime. Low pH is one of the most frequent
causes of poor corn yields in Alabama. Acid soils
can result in reduced root growth, reduced nutrient
availability, toxicities of some elements, and poor
activity of some herbicides. For good corn growth,
maintain the soil at a pH of 5.8 to 6.5. Base your
lime applications entirely on soil test recommendations. Any needed lime will be most efficient if applied and incorporated 2 to 4 months before planting, but application and incorporation just before
planting is helpful if earlier application was not
made.
Phosphorus and potassium Most Alabama soils
require an application of phosphorus and/or potassium for good com production. The amount needed
CIRCULAR ANR-503
Grain yields respond to high levels of nitrogen
application in years when rainfall is abnndant and
distributed throughout the growing season. There
is also a strong interaction between nitrogen fertilization and plant population with regard to grain yield.
Low plant populations frequently limit grain yield
in situations where soil moisture and levels of
nitrogen fertilization are high enough to produce
good yields.
The optimum economic rates of nitrogen fertilization are usually near, but may not be identical
to, the rates that result in the maximum-yield
response. At high application rates, additional
nitrogen may produce a slight yield response, but
this may not be enough to pay for the additional
expense. A worksheet for determining optimum
rates of nitrogen is shown below.
Standard rate .............. 120 pounds per acre
For productive sandy soils, add 30
pounds
If crop follows good soybeans (greater
than 40 bushels per acre), subtract 30
pounds.
If crop follows a good winter legume
which is turned under, subtract 30
pounds.
If dryland yield potential is greater
than 150 bushels per acres, add 60
pounds.
If crop is irrigated, add 60 pounds.
If starter fertilizer is used, add 20 to 30
pounds.
Total nitrogen recommended for
season (final rate should not exceed
200 pounds per acre).
Corn that follows soybeans in a rotation may
benefit from nitrogen fixed by the soybeans. The
amount of nitrogen available to corn from this
source is small (usually 20 to 30 pounds per acre).
Other benefits of the rotation are more valuable than
the nitrogen obtained from the soybeans.
Timing and sources of nitrogen. The com plant
takes up nitrogen throughout the growing season,
but the period of most rapid uptake is just before
and during the silking and tasseling period. If all
of the nitrogen is applied at planting time, much of
it may be lost to leaching or denitrification, especially on deep sandy soils or soils with poor drainage.
These losses can be reduced by applying about onethird of the total nitrogen at planting and sidedressing and broadcasling lhe remainder in one or more
applications when the plants are aboul knee-high.
Different sources of nitrogen should be equally effective if application requirements are met and equal
units of nitrogen are applied (see Thble 1).
Secondary micronutrients. Apply at least 10
pounds of sulfur per acre at planting. This is particularly important on sandy soils of southern
Alabama and on the soils of the sandstone plateau
of northern Alabama. Because sulfur deficiencies are
most likely to occur early in the season, a starter
fertilizer containing sulfur is the most effective way
of applying sulfur. Blended or granular fertilizers
containing sulfur may also be broadcast before
planting.
Zinc deficiencies occur primarily in early spring
on sandy soils where the pH is above 6.0 or when
lime has recently been applied. Th avoid this problem, apply 3 pounds per acre of zinc at planting.
A starter fertilizer would be the most effective way
of applying zinc, but it can be broadcast with other
complete fertilizers.
Table 1. Common Nitrogen Fertilizers For Corn.
Fertilizer
Percent
Of Nitrogen
Form
Remarks
Low price. Inject at least 6 inches
deep in soil.
Can be broadcast and left on surface.
Can be broadcast and left on surface
except on alkaline soils.
Solutions containing over 19 percent
N will contain urea as one of the
components. Inject these solutions or
incorporate them in the soil.
Can be broadcast and left on surface.
Subject to volatilization. Do not leave
on the soil surface.
Anhydrous ammonia
82
Compressed gas
Ammonium nitrate
Ammonium sulfate
33.5
20.5
Dry solid
Dry solid
Nitrogen solutions
Variable
Sodium nitrate
Urea
16
46
Liquid
Dry solid
Dry solid
Starter fertilizers. Starter fertilizers provide
readily available nitrogen and phosphorus to young
com plants in early spring when growing conditions
may not be ideal. Use starters when planling very
ea rly in cold soils or when planting in minimum
till or no-till systems. Starter fertilizers promote
earlier maturity, aid in weed control by promoting
early vigorous growth, and sometimes result in a
yield increase.
Apply 20 to 30 pounds per acre of nitrogen IN)
and 20 pounds of phosphorus (P2 0s) in a band 2
to 3 inches below and 2 to 3 inches to the side of
the seed. Fertilizer may be dribbled to the side of
the row at planting or applied in a subsoil slit just
below the seed, but these methods are not as effective as banding. Sulfur and zinc may be effectively
applied in the starter fertilizer. A complete granular
fertilizer such as 13-13-13, a liquid such as 10-34-0,
or nitrogen solutions may be used as starters.
Research in Alabama has shown that most of the
crop response is to the nitrogen and only occasionally to the phosphorus.
Tillage
Conventional methods of seedbed preparation
may involve either plowing, chiseling, disking, harrowing, or combinations of these tillage operations.
The purpose of tillage is to control weeds. Any unnecessary tillage is an expense that cannot be
recovered.
Deep tilage, deep chiseling, and in-row subsoiling have become popular with some growers in re- ·
cent years. These techniques are likely to be
beneficial when they break through a zone of soil
compaction or hardpan that would otherwise restrict
root growth.
Deep tillage operations are likely to have little
or no beneficial effect in fields that don't have compaction problems or where the compacted zone is
too deep to be broken through. Crops grown on sandy soils of the coastal plains are most likely to respond to deep tillage. Crops grown on the fine textured soils of the Black Belt and the Thnnessee Valley
are not likely to respond to subsoiling.
No-tillage planting is being successfully used by
some Alabama producers, and the acreage of notill com appears to be increasing in the state. Reductions in erosion losses and in the number of trips
over a field, as well as saving time during planting,
inake no-till planting attractive to many growers. Notill systems require timely management and should
not be undertaken without first investigating the
management requirements. For additional information on tillage practices, see Extension Circulars
ANR-40, "No-Tillage Com In Alabama" and ANR-41,
"Tillage Th Correct Soil Compaction."
Hybrid Selection
Do not select your hybrids based on yielding
ability alone. Hybrids which have good yielding
ability can vary considerably in other important
traits such as lodging resistance, maturity, and
resistance to disease.
Yielding ability is a complex trait and is influenced by many environmental factors. It is not
unusual for the performance of a particular hybrid
to vary considerably from year to year depending
on weather conditions and disease and insect incidence. For this reason, the use of data from a single
year may be misleading.
Detailed information on yields and other variety
performance traits is available in lhe annual Corn
Hybrid Per{onnance Report published by the Department of Agronomy and Soils, Alabama Agricullural
Experiment Station, Auburn University. Copies of
the current report are available at your county
Extension office.
Planting Dates And Depths
Do not plant corn until the soil temperature at
a depth of 2 inches is 55° F. or above and there is
little danger of a freeze or heavy frost. Wilh these
points in mind, the following dates are suggested
for planting corn in Alabama:
South Alabama: March 1 - April 20
Central Alabama: March 15 -April 30
North Alabama: March 25- May 15
Planting in late February may be desirable along
the Gulf Coast.
Place com seed deep enough to obtain favorable
moisture conditions for germination but shallow
enough to allow for quick emergence. At early planting dates when soils are moist and cold, plant com
at a depth of 1 to 1'12 inches. Check the planting
depth and seed spacing periodically during the planting operation.
Plant Populations And Row Width
Corn grain yields can be markedly reduced by
very low plant populations. Yield reductions due to
an extremely high population can occur but are
much less frequent in Alabama than reductions due
to low populations. Optimum plant populations for
corn are influenced by a number of factors
including:
Hybrids. The optimum population differs from
hybrid to hybrid. Recently released hybrids tend to
do best at populations somewhal higher than older
hybrids.
Fertility levels. Increased populations are often
needed to obtain the maximum benefit from high
fertility levels (especially high N levels).
Planting dates. Corn planted very early tends
to be shorter at maturity than later-planted corn.
Such corn tends to lodge less and generally benefits
from slightly higher populations.
Before making a decision regarding the plant
population for a particular field, consider the many
factors that influence optimum population. Nonuniform stands and low plant populations frequently
limit corn yields in Alabama. Most non-irrigated
hybrids will produce highest yields at populations
of 16,000 to 24,000 mature plants per acre.
The two ways to alter plant populations are: 1J
to vary spacing within rows; or 2) to vary row
widths. Various combinations of seed spacing and
row widths to obtain different plant populations are
indicated in Thble 2.
Table 2. Seed Spacing To Obtain Various Plant Populations.
Population
Seeds Planted
Per Acre*
16,000
18,000
20,000
22,000
24,000
26,000
28,000
18,000
21,200
23,500
25,900
28,200
30,600
32,900
Inches Apart In The Row
Row Width !Inches)
30
36
38
40
42
11.00
9.75
9.00
8.00
7.50
6.75
6.25
9.25
8.25
7.50
6. 75
6.25
5.75
5.25
8.75
7.75
7.00
6.25
5.75
5.50
5.00
8.25
7.50
6.75
6.00
5.50
5.00
4. 75
8.00
7.00
6.25
5. 75
5.25
5.00
4.50
• Assuming that 85 percent of the seeds produce plants.
Thble 2 indicates the needed seed spacing based
on the assumption that about 5 percent of the
planted seed will not produce mature plants due to
germination failure and stand loss to insects,
diseases, and other causes. Under poor seedbed conditions and under no-tillage planting conditions, the
percentage of seed failure may be even higher.
The
~1Aiabama
E,i.7Cooperative
Extension Service
AUBURN UNIVERSITY
Under such conditions, increase seeding rates to
allow for 20 to 25 percent seed failure.
In past years, most corn was produced in rows
spaced 38 to 42 inches apart, and most of the production and harvesting equipment available was
designed for these widths. Research and farm experience in recent years, however, has indicated that
yields may be increased when row widths are
reduced below 40 inches.
The higher the level of management, the more
likely it becomes that narrowing rows will have a
positive impact on yields. If equipment is available
which will harvest narrow rows (30 to 40 inches),
it is usually an advantage to use narrower row
widths.
Soil Insecticides-N ematicides
The use of soil insecticides-nematicides is not
recommended as a routine precautionary measure
for all com in Alabama. There are several situations,
however, where their use may be beneficial. If soil
insects or nematodes are known to be a problem
in a field at planting time, treatment is suggested.
Treatment may also be justified in high-risk situations such as irrigated com grown at high fertility
levels, very early planted corn, or no-till corn.
Always follow label directions in applying such
materials.
Weed And Insect Control
Good weed and insect control is essential for producing high yields of com. Weeds compete not only
for water but also for nutrients and sunlight. Insects
can also cause serious yield reductions in com in
Alabama. For more information on weed and insect
management, see Extension Circular ANR-428,
"Corn Pest Management:'
CIRCUlAR ANR-503
Issued in furtherance of Cooperative Extension worl< in agriculture and home economics, Ac1s of May 8 and June l1, 1914,
in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension Service, Auburn University, Ann
E. Thompson, Director, offer.; educational programs and materials to all people without regard to race, color, national origin,
sex, age, or handicap and is an equal opportunity employer.
UPS,7M00,8:88,ANR-503