Page 16—Corn Talk, Lancaster Farming, Saturday, April 17,1993
Nitrogen Management
Douglas B. Beegle
Associate Professor
Agronomy
Penn State
Good nitrogen (N) manage
ment is a critical component of
successful com production.
In addition to being one of
the largest economic inputs into
producing a com crop, it is
often the most limiting farmer
controlled factor in producing
com.
Nitrogen management can
be broken down into decisions
on how much N to apply, what
source of N to apply, when to
apply it, and how to apply it.
Rates
Recommended N rates for
com are 1 to 1.1 pounds of N
per bushel of expected grain
yield or 7 pounds of N per ton of
expected silage yield. Thus,
one of the key factors in deter
mining the appropriate N rate is
having a reasonable estimate of
expected yield.
Sources
There are numerous sources
of N that can be effectively
used to meet the N requirement
of a com crop. The common N
fertilizer sources include urea
(46 percent N), UAN solution
nitrogen (30 percent N), ammo
nium nitrate (34 percent N),
ammonium sulfate (21 percent
N), and anhydrous ammonia
(82 percent N).
If used properly, these are all
(Continued from Page 15)
ter the expansion, the higher the
quality.
Moisture content should be
13.5 to 14 percent for best
results. Varieties differ as to
quality, which also includes fla
vor, tenderness, absence of
hulls, color, and shape.
Shape can vary from
mushroom-spherical to butterf
ly. The confection industry usu
ally prefers the spherical
easier to coat with flavors or
syrups. The butterfly-shaped
popcorn has a better “mouth
feel” and is preferred for on
premises sales, as in theaters.
For more information, con
tact the Popcorn Institute, 401
N. Michigan Ave., Chicago, IL
60611, (312-644-6610).
Hi-Lysine Corn
Com is a major staple in
many underdeveloped coun
tries. As dent com is a relatively
poor source of protein, many
consumers have to supplement
their diets with other protein
sources, such as beans.
Most of the protein in com is
zein, which cannot be efficient
ly digested by humans and
other nonruminant (single sto
mached) animals such as pigs
and chickens.
Zein exists at the expense of
lysine and tryptophan, which
tend to be very low in dent com.
Lysine and tryptophan, two of
eight essential amino acids that
very good sources of N for
growing com. There are how
ever, some special
considerations,
Urea and UAN can both lose
significant amounts of N by
ammonia volatilization if these
sources are not incorporated
soon after application. Incorpo
ration by tillage or 'A inch of
soaking rain within 48 hours
will minimize this loss. With
out incorporation, losses as
high as 30 percent of the
applied N within a week have
been measured.
With UAN, this loss can be
reduced by banding the solu
tion rather than spraying it on
the soil surface. Ammonium
nitrate and ammonium sulfate
do not release volatile ammoni
a, therefore they do not need to
be incorporated. Anhydrous
ammonia is a gaseous source of
N that must be injected or the
gas will be lost into the air.
Manure is also a very signif
icant source of N on many com
farms. The N content of manure
will vary greatly thus, man
ure analysis is critical to confi
dently utilizing the N from
manure.
Book values for manure N
are 10 pounds N per ton for
dairy manure, 14 pounds per
ton for swine manured and 60
pounds per ton for poultry man
ure. Actual values may vary as
much as 100 percent from these
values, however.
Only about 50 percent of the
N in most manures (75 percent
in poultry) is available the year
Small-Scale Ag
nonruminams can’t synthesize
on their own, must be obtained
from food they eat.
In 1963, scientists at Purdue
University found that the com
strains containing opaque-2
(02) genes contained lesser
amounts of zein and greater
amounts of lysine and trypto
phan in their endosperms than
dent com. Opaque-2 kernels,
however, appear dull and tend
to have soft textures and very
little hard endosperm. It makes
them difficult to harvest and
subject to attack by various
pests.
Opaque-2 varieties also tend
to have lower yields and must
be isolated from other corns to
retain protein quality.
High-Oil Corn
The highly polyunsaturated
and high linoleic acid content
of com oil makes it an excellent
energy and essential fatty acid
source for both humans and
livestock.
Livestock feeders may be
interested in varieties with gre
ater oil contents. Such varieties
have more calories, bringing
greater gains per feed unit.
Most hybrid dent corns will
average between 3.5 and 6.0
percent oil. Varieties with oil
contents greater than 6.0 per
cent tend to have lower yields.
Oil quality is dependent on the
amounts of unsaturated and
saturated fatty acids it contains.
For Corn
the manure is spread. This
available fraction is mostly
urea and therefore is subject to
volatilization losses as dis
cussed earlier for urea fertilizer.
For this reason, the availability
of manure N will depend on
incorporation and ranges from
50 percent for immediate incor
poration to 20 percent for no
incorporation. The fraction of
manure that is not available the
year the manure is applied will
become available over the next
several years.
Legumes are also a major
source of N for com produc
tion. Legumes such as alfalfa
and soybeans fix all of their N
needs, plus leave considerable
N in the soil that can be used by
the following crop in the rota
tion. An alfalfa crop, with at
least SO percent of the alfalfa
remaining, will supply all but
about 20 to 40 pounds of the N
requirement of the following
com crop. Even a very poor
stand of alfalfa will supply 40
to 60 pounds of N per acre to the
following com crop. A soybean
crop will supply about one
pound of N per bushel of soy
beans for use by the following
com crop.
Timing
The liming of N fertilizer
application to com is important
to reduce the potential for loss
of the applied N. Nitrogen
should be applied as close to the
time of crop uptake as practical
to avoid potential losses of the
N before the crop can use it. For
Alternative:
Oils high in linolcic acid and
low in oleic, palmitic, and
stearic acids are preferred for
human diets.
For information on breeding
high-oil com, contact John
Dudley, Agronomy Depart
ment, S-l 12 Turner Hall, 1102
South Goodwin Avenue, Uni
versity of Illinois, Urbana, IL
61801. (217) 333-9640.
Waxy Endosperm
Corns
Waxy endosperm hybrids
contain 100 percent amylopec
tin starch the normal dent
com ratio is 72 percent amy
lopectin and 28 percent amyl
ose. The waxy (wx) mutant was
found in China in 1909 but was
not fuily developed until 1936,
when researchers from lowa
State University noted its
unique properties and started
developing hybrids.
Steers make better gains
when fed waxy endosperm com
rather than dent com. The sta
bility and clarity of amylopec
tin starch make it highly suit
able as a food thickener.
For more information on
food processing aspects, con
tact Edith Munro, Com Refin
ers Association, 1100 Connec
ticut Avenue NW., Suite 1120,
Washington, DC 20036, (202)
331-1634.
Blue Corn
Atole, tortillas, com chips,
and other com products have
(O(D3M TAILI MIWO
%
com, this means that the ideal
application time for most of the
N would be when the com is 12
to 18 inches tall.
This is usually after the
spring wet conditions when N
losses are greatest and just
before the period of rapid
growth by the com. If the field
has, a history of manure or
legumes, all of the N can be
applied at this time. If there is
no history of manure or
legumes, then 30 to 50 percent
of the N should be applied near
to planting.
When delayed application is
not practical, the N should be
applied as near to planting time
as possible. The longer before
planting that N is applied, the
greater the potential for signif
icant loss of the N before the
plant can use it.
Applying N in the fall for
com is not recommended
because of the high N losses
that can occur before the crop is
even planted.
Methods
Finally, the method of N
application must be considered.
If the N source contains urea
(urea, UAN, or manure), then
incorporation either by tillage
or by rain is important, regard
less of application timing, to
reduce volatilization losses.
Also, banding can reduce this
volatilization loss.
For delayed application, the
best method of application is
Specialty Corns
been the backbone of most trad
itional and present-day Native
American and Mexican Ameri
can cuisines.
Blue com and other flour
corns historically represented
the major kernel type of com
ground into “harinas” flour and
meals in the American South
west. But dent corns, both
white and yellow, now domi
nate the market. However, the
blue corns are finding new
market outlets.
Although Pueblo tribes have
historically grown many diffe
rent colored corns, blue com is
one of the most important, both
as food and for religious
purposes.
Unlike most commercial yel
low hybrid dent corns that can
yield 8,000 to 10,000 pounds of
grain per acre, blue com is open
pollinated and characterized by
relatively low yields of 1,000 to
4,000 pounds per acre. It also
lends to lodge, making machine
harvest somewhat difficult.
Blue com has a coarser,
sweeter, and nuttier taste than
other corns grown for flour or
meal. Us grainier consistency
results in a somewhat denser
tortilla than those made from
white or yellow com flour.
Research of the New Mexico
Cooperative Extension Service
found blue com, like Opaque-2
com, higher in lysine than
either white or yellow dent com
varieties used in tortillas. Most
injecting the N between every
row of com. A close second
best is banding the N on the sur
face between every row. Nitro
gen can be banded between
every other row but to be effec
tive it must be banded exactly
in the middle between the rows.
The N can also be broadcast
over the growing com and cul
tivated m or applied just before
a rain to provide incorporation.
This method will result in some
burning of the com but this
does not typically have any
negative effect on the final
yield.
Good N management
depends on determining the
correct amount of N to apply
based on a sound estimate of
expected yield, then choosing a
high quality economical source
of N to meet this need.
Remember to include man
ure and legume N in this deci
sion. The N should be applied
as close to the time of crop need
as practical.
Finally, the proper method of
application must be used for the
material that has been chosen to
minimize losses and thus max
imize crop utilization of the N.
Jue com varieties were also
found to be high in iron and
zinc.
Blue com flours and meals
have traditionally been used in
making tortillas and com chips.
Native American products less
well known include piki or pap
er bread, chaqueque (similar to
com meal mush), aide (com
meal drink), and nixtamal or
lime hominy used in making
stews.
Newer products include pan
cake and muffin mixes and com
flakes.
For more information, con
tact George Dickerson, New
Mexico Cooperative Extension
Service, (505) 275-2576.
Corn Cob
Corns
Although most com grown
in the United States is for grain
or silage, at least one hybrid
variety is grown for making
com cob pipes. Cobs should be
at best l-'/i inches in diameter
and long enough to make at
least two bowls (2 inches each).
The diameter of the cob should
be relatively uniform.
Cobs should be woody and
sufficiently hard to keep smok
ing tobacco from burning
through the bowl.
For more information, con
tact Harry Minor, the Agro
nomy Department, Extension
Service, Waters Hall, Universi
ty of Missouri, Columbia, MO
65211, (314) 882-2001.