Photo by: Ron Nichols, USDA-NRCS |
Abstract
This publication discusses production of organic field corn, addressing soil fertility, crop rotation, disease and pest management, and economic and marketing considerations.
Table of Contents
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Introduction
The term organic farming describes systems that work to
mimic and optimize natural processes for the production of crops.
Organic growers utilize a wide range of cultural practices and natural
inputs to manage crops in a manner they consider safe for the environment
and the consumer. Synthetic pesticides and standard commercial fertilizers
are not consistent with the organic approach and are prohibited.
For more information on organic farming and the current regulations
that govern it, please see ATTRA’s Organic Crop Production Overview and Organic
Farm Certification and the National Organic Program publications.
Corn is not especially difficult to produce using organic methods,
though focusing on this single crop is a poor starting point and
leads to a misunderstanding of how organic farming works. When it
comes to the production of agronomic and vegetable crops, organic
growing typically entails an integrated rotation of different crops
that (ideally) complement or compensate for each other. Such production
systems are further enhanced when livestock enterprises that involve
grazing and that generate manures are also part of the scheme.
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Fertility
Compared to other crops, corn is a moderate to heavy consumer of
most nutrients, especially nitrogen (N). At a yield level of 150
Bu., the harvested grain is estimated to contain at least 135 lbs.
of N. (1) Supplying adequate nitrogen is one
of the top challenges for organic corn producers.
Crop Rotation
The use of planned crop rotations that include forage legumes is
the key means by which nitrogen is supplied to an organic system.
The most effective of these legumes in most U.S. locations is alfalfa,
though other species are also effective. A well-established alfalfa
stand, left in place for two or more years, can supply a high level
of residual, biologically-fixed nitrogen for corn and other non-leguminous
crops.
Non-forage legumes—such as soybeans—are only moderate
nitrogen-fixers and do not supply the amounts of N needed for sustainable
rotations. Furthermore, most of the nitrogen that soybeans fix is
removed with the harvested portion of the crop, leaving very little
residual N for subsequent crops. This is not to downplay soybeans’
contribution to nitrogen fertility; the following crop often exhibits
some residual benefit. (One traditional rule of thumb suggests that
there is a residual nitrogen gain of only 1 lb. N for each bushel
of harvested soybean yield.) The key point of this discussion is
that soybeans should not be considered an equal substitute for legume
forages in standard rotations.
To get a good idea of how to design crop rotations for optimum
fertility (and pest management), see the ATTRA publication Sustainable
Corn and Soybean Production.
Cover Crops & Green Manures
Growing legumes as green-manure crops is another means of getting
more biologically-fixed nitrogen into the rotation to support corn
production. Green-manuring fell out of favor with farmers who could
not afford to dedicate a full cash-crop season to this soil-improving
practice. Fortunately, green-manuring has been revived in recent
years as new interplanting and off-season cover-cropping schemes
have emerged. These allow the farmer to grow and use green-manure
crops with minimal disruption to the cash-crop cycle.
Numerous species and mixtures of species can be used as effective
cover crops/green manures. For example, research from the University
of Maryland has suggested that a fall-seeded mix of a legume and
a grass (e.g., vetch and rye) may be optimal. Such cover-crop mixtures
self-adjust according to residual soil nitrogen levels. Where natural
soil nitrogen or fertilizer nitrogen levels are high, grasses will
dominate and serve as a “catch crop.” Where nitrogen
levels are low, legumes will outgrow grasses and fix additional
nitrogen for use by subsequent crops. (2)
Some cover-cropping schemes entail ridge-tillage and no-till planting
strategies, in which a winter cover crop is either winter-killed
or mechanically killed prior to establishing the crop. ATTRA has
additional information on no-till, ridge-till, and non-chemical
methods for killing cover crops. For additional information on cover
crops, please see ATTRA’s Overview
of Cover Crops and Green Manures.
Livestock Manures
Farms that produce livestock or are in proximity to confinement
operations have the advantage of access to animal wastes that contain
nitrogen, other major nutrients, and organic matter. The precise
amount of nitrogen in manure varies considerably, depending on livestock
species, feed formulation, and manure handling. Proper application
and soil incorporation of fresh manures assures the maximum capture
and delivery of nitrogen to the crop. Therefore, manuring is often
done just prior to corn planting in crop rotations.
Generally, manures have their strongest effect on the corn crop
if applied just in advance of planting. To achieve maximum recovery
of nutrients from spread manure, sheet composting is the best option.
Sheet composting entails plowing or otherwise incorporating the
manure into the soil as soon as possible after spreading. Research
has shown that solid raw manure will lose about 21% of its nitrogen
to the atmosphere if spread and left for four days; soil incorporation
reduces that loss to only 5%. (3) However, since
excessive tillage is discouraged in sustainable systems, options
for sheet composting may be limited on some farms. The next best
option appears to be spreading onto growing cover crops in advance
of the corn crop. This reduces the chances of loss to surface erosion
and cuts leaching significantly.
Application of raw manure is prohibited within 90 days of corn
harvest when the crop is to be used for human consumption (4)—usually
not a problem, considering corn’s long growing season and
the fact that most field corn is produced for livestock feed.
The 1990 Organic Foods Production Act mandates that manure not
be applied in any way that could significantly contaminate water
resources with nitrates or bacteria. (4) Composting
is a means of stabilizing and enhancing livestock wastes for storage,
which avoids certain problems inherent in applying fresh manure.
Composts, though lower in total nitrogen, are a more balanced fertilizer
and are more useful in building soil fertility over time. For additional
information on composting, please see ATTRA’s Farm-Scale
Composting Resource List, Biodynamic
Farming and Compost Preparation, and Worms
for Composting (Vermicomposting) publications.
For additional information on manure, including nutrient analyses,
hazards, spreader calibration, and other details, please see
ATTRA’s Manures
for Organic Crop Production.
Supplementary Nitrogen Fertilizers
Some organic growers provide supplemental nitrogen in the form
of approved animal or plant byproducts, though this is typically
too expensive for regular field corn production. Among the materials
occasionally used are:
- Cottonseed meal. Approximate nutrient analysis
of 7-2-2. Releases nutrients at a medium to slow rate; tends to
make soil acidic. Because of heavy chemical use in cotton culture
and the use of solvents to extract the meal, there are severe
restrictions on its use in certified organic production.
- Feather meal. Approximate nutrient analysis
of 13-0-0. A slow-release material.
- Blood meal. Approximate nutrient analysis of
12-1.3-0.7. Medium-release. Typically very expensive.
- Fish meal. Approximate nutrient analysis of
10-2-2. Slow- to medium-release.
Various blended commercial organic fertilizers are sometimes used
in certified production to provide nitrogen. Many of these are listed
in ATTRA’s Sources
of Organic Fertilizers and Amendments. Note that many
commercial and “waste” products may have restrictions
on their use in organic farming. Organic growers should check with
their certifying agency before purchasing and applying new products.
The Benefits of an Organic System
Crop rotation, cover cropping, green manuring, use of livestock
manures, and composting are all soil-building practices that do
much more than provide nitrogen. By adding organic matter and stimulating
biological activity in the soil, these practices make mineral nutrients
more available to plants, generate the microbial production of plant-beneficial
chemicals (e.g., streptomycin), and improve soil tilth. Manuring,
in particular, cycles essential macro-and micronutrients back onto
the fields.
Rock Minerals—Lime
Because manures are imbalanced fertilizers, and because not all
soils are equally rich in native fertility, organic farmers often
need to import supplementary mineral nutrients to assure balanced
crop nutrition. These inputs are commonly in the form of moderately
priced, minimally processed rock powders.
The most commonly used rock powders in organic systems are various
agricultural liming materials. Agricultural lime is used to neutralize
the acidity of soils and to provide plant nutrients—mostly
calcium and magnesium. There is considerable disagreement in agronomic
circles as to which liming materials are most appropriate under
different circumstances. Most of the controversy centers on the
use or possible overuse of dolomitic lime, which contains high percentages
of magnesium relative to calcium. Excessive soil magnesium levels
are believed to have detrimental effects on soil structure and also
to produce nutritionally imbalanced livestock feed.
The most conservative approach to lime recommendations—one
popular among many organic growers—is based on measuring the
ratios of positively charged ions in the soil. This is known as
the Albrecht or CEC (Cation Exchange Capacity) System. It is based
on the philosophy that the primary reason to add lime is to supply
essential nutrients and that soil acidity will reach a desired level
when all minerals are present in proper balance. The possible overuse
of dolomitic lime is avoided when this approach is followed.
Lime and other rock-mineral powders should only be applied with
the guidance provided by soil testing. To determine what type of
recommendation one will receive from a soil testing laboratory,
it is often necessary to ask in advance. A listing of laboratories
that use the Albrecht System is provided in the ATTRA publication Alternative Soil
Testing Laboratories. ATTRA also has additional information
on the Albrecht philosophy for managing soil fertility.
Rock Minerals—Other Major Sources
When supplementary phosphates are required in an organic system,
they are usually supplied as rock phosphate. Rock phosphates are
of several types and grades. It is most common to speak in terms
of colloidal soft-rock phosphate and hard-rock phosphate. Hard-rock
phosphate is available from several geological sources and varies
considerably in appearance and soil reactivity. Black rock phosphate,
from North Carolina, is one form of natural phosphate rock that
has a reputation for good performance in the field, is easy to handle,
and is reasonably easy to find in the marketplace.
Soft-rock phosphate or colloidal phosphate is a dried clay-based
byproduct of hard-rock mining. Although powdery and difficult to
handle, it has a good reputation as a phosphate source on a wide
range of soils.
Gypsum (calcium sulfate) is often referred to as a liming material
because of its calcium content. However, since it does not neutralize
soil acidity, this designation is technically incorrect. Gypsum
can be used to supply calcium and sulfur. It is especially useful
on high pH and sodic soils, and is reputed to improve soil structure
under some conditions.
Supplemental potassium is generally supplied in the form of sulfate
of potash-magnesia, select sources of mined potassium sulfate, or
various sources of fly ash in blended organic fertilizers.
There are other rock mineral powders available for agricultural
use, including greensand, lava sand, granite dust, etc. Generally
speaking, most are relatively expensive and not economical for agronomic
crops.
Unique Soil Products
Several other soil additives are available to organic growers as
soil fertility enhancers. These include humates, humic acids, surfactants,
bioactivators, Biodynamic preparations, and others. These products
are often expensive and performance can be highly specific to circumstances.
For more details, please see the ATTRA publications Alternative
Soil Amendments and Sources
of Organic Fertilizers and Amendments.
Foliar Fertilization
Though the practice is somewhat controversial, some conventional
and organic growers routinely supplement crop nutrition via foliar
feeding. There are several approved organic fertilizers and materials
that can be used. Please see ATTRA’s Foliar
Fertilization publication if you want more details.
Summary Comments on Organic Fertility Management for Corn
Organic management of soil fertility is most economical when it
is based on biologically fixed nitrogen, recycled nutrients (e.g.,
livestock manures) and a biologically active soil. Importing nutrients
from off-farm can be expensive and must be done with careful planning
to assure optimum use of physical and financial resources. Strongly
suggested as a basic guide is ATTRA’s Sustainable
Soil Management publication.
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Weed Management
Reasonable control of weeds must be maintained to assure economic
corn yields. As this information is discussed in detail in other
ATTRA materials, it will not be covered here. Please see Sustainable
Corn and Soybean Production and Principles of Sustainable Weed Management for Croplands. ATTRA also
has detailed information available on flaming as a weed control
technology.
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Insect Pest Management
Insect pests can be a major problem in corn production. While corn
may be attacked by a wide number of insects, we will here focus
on those that are considered a major problem in most areas of the
country. These include European corn borer, corn rootworm, and cutworms.
A few of the technologies that will be discussed are too expensive
for use with standard field corn, but may be economical for production
of high-value specialty corns.
European Corn Borer
The European corn borer, Ostrinia nubilalis, overwinters
as a fully grown larva in the stems and ears of corn plants, usually
just above the ground surface. As the weather warms in the spring,
the larvae pupate, emerging later as adult moths. The adults mate,
and the females lay eggs on the underside of the corn leaves. (5)
The smallest larval stages of the first generation feed on leaves
and on other exposed plant tissues. After the larvae are half-grown,
they bore into the stalk, ear, or the thicker parts of the leaf
stem. Once inside the plant, European corn borers (ECB) are difficult
to control, so most management efforts are directed toward the egg
and early larval stages.
Effects of Crop Management
It is interesting
to note that ECB is one pest problem directly affected by soil
management and fertilization. Research done at Ohio State University
found that ECB adults laid 18 times as many eggs on corn plants
grown on conventionally managed soils as on corn raised on organically
managed soils. (6) This confirms similar observations
made in the late 1970s during research comparing organic and conventional
farms in the western corn belt. (7) The precise
modes of action that hinder ECB remain a matter of speculation,
but clearly, corn under organic management schemes suffers less
damage from this pest.
Cultural Controls
Since ECB has been found
to feed on over 200 species of plants (including potatoes, beans,
celery, beets, spinach, and rhubarb), crop rotation
is only marginally effective for suppression. However, rotation
can be somewhat successful when most of the acreage involved is
in non-susceptible crops. Forage legumes (with the exception of
cowpeas) suffer little damage from ECB and are quite useful in
such rotation schemes.
Since the pest overwinters in above-ground crop residue, sanitation
procedures are useful in reducing the number of corn
borers that emerge the following spring. Standard disking and
plowing of residues do not appear adequate, however. Specific
sanitation techniques that have demonstrated efficacy for reducing
ECB populations include:
- Ensiling the corn crop while leaving two inches or less of
stubble
- Thoroughly shredding all crop residue prior to plowing
- Clean plowing to thoroughly bury all corn residues
- Burning corn residues in the field
Note that most of these sanitation practices—while effective
at reducing emergence from the field—will not guarantee
reduction of damage in a subsequent crop, because of the mobility
of this pest. Also, these practices are inconsistent with emerging
concepts of sustainable farming that promote the maintenance of
soil cover and the conservation of crop residues. Growers are
encouraged to view these solely as transition practices and to
focus on other strategies.
In regions where only one generation of ECB occurs (principally
the North Central states), late planting can
be effective.
Biological Controls
A number of natural parasites,
including Ichneumonid, Braconid, and Trichogramma wasps, help
to control ECB populations in healthy agroecosystems where pesticide
use is minimal. Several generalist predators such as assassin
bugs, damsel bugs, mantids, and spiders also assist. Populations
of these beneficials can be enhanced by management practices designed
to support their presence and activity. Such practices include
cover cropping, strip cropping, and the management of adjacent
vegetation to provide refugia for predators and parasites. Details
on refugia management are provided in the ATTRA
publication Farmscaping
to Enhance Biological Control.
In higher-value sweet corn or specialty corn crops, there may
be economic justification for the introduction of insectary-reared
parasites. (8) Insectaries have additional
information about timing, release rates, and the preferred Trichogramma species for a specific area. Farmscaping strategies—such
as interseeded cover crops—can add significantly to the
effectiveness of released beneficials. Research on irrigated seed-corn
fields found that annual ryegrass, overseeded two days after corn
planting, moderated soil surface temperatures and created a desirable
environment for Trichogramma. (9)
Please note that making the best use of parasite release (and
other controls for that matter) requires field monitoring and
record keeping. Trapping of adult moths using pheromone traps
is one tool that can be used. Also, effective monitoring should
include the inspection of areas adjacent to the field, in addition
to scouting the field itself. (10) For more
information on monitoring, trapping, and related technologies,
ATTRA’s Biointensive
Integrated Pest Management publication is suggested.
Alternative Pesticides
Bacillus thuringiensis (Bt) is a biological pesticide capable of killing many lepidopterous
larvae, including European corn borer. Bt must be ingested in
adequate amounts to be effective, however. Larvae that bore directly
into the stalk may not eat enough of the material to be affected.
Some of the most effective formulations are granular—applied
so that they collect on the leaves and roll into the whorls. (5)
Bt products are widely available and can usually be found through
local sources under a variety of trade names including Javelin™,
Dipel™, and Thuricide™.
Research has also found ECB to be susceptible to the fungus Beauveria
bassiana, which has become increasingly available as a commercial
biopesticide for other crops. The fungus, which already exists
at low populations in healthy corn agroecosystems, is capable
of “infecting” the corn plant. Through this infection
an endophytic relationship is established between the
fungus and plant. Corn yield and performance are not compromised.
However, any European corn borer feeding on the plant will contract
the fungus, resulting in the insect’s eventual demise. Preliminary
research involving applications of B. bassiana at the
whorl stage appears to reduce ECB tunneling by about 50%. (11,
12) Further research indicates that combining
Bt with B. bassiana can provide higher levels of ECB
control than either product alone. (13)
Other sources suggest that several botanical pesticides—pyrethrin,
ryania, and sabadilla—are
also effective against ECB larvae. (14) However,
these are rarely used in field-corn production because of their
high cost and the fact that botanicals are more hazardous to beneficial
organisms than biologicals.
Varietal Resistance
Selecting varieties resistant—or
at least tolerant—to attack by European corn borer is one
means of reducing damage by this pest. While this strategy has
been advised for decades, the release of genetically engineered
varieties has added another dimension. What separates these new
varieties from traditional resistant cultivars is the presence
of a gene capable of producing the Bacillus thuringiensis
biotoxin, obtained originally from the bacterium with the same
name. Called Bt corn, these transgenic plants
simply poison any caterpillar pest that feeds on them.
Bt corn does not provide a simple solution, however. Just as
plants can evolve or be bred to resist certain pests, pests can
evolve resistance to the natural and synthetic poisons humans
use to control them. One of the major concerns raised with Bt
corn is that widespread use can easily set the stage for resistance
to develop in ECB and other lepidopterous pests. The mechanisms
for resistance are the same as those that occur when a chemical
pesticide is too widely used—surviving, resistant pest individuals
are able to concentrate, interbreed, and multiply, thereby producing
a generation with much less sensitivity to the pesticide. Growing
genetically engineered Bt crops is comparable to a sustained 7-
to 10-day schedule of spraying with the same pesticide, beginning
at planting and ending when the crop residue decays sometime after
harvest—a full season’s sustained exposure to Bacillus
thuringiensis.
The conventional agriculture community is not unaware of the
risk. Bt corn growers are advised to plant a percentage of their
corn acreage to non-Bt varieties—recommendations vary from
as low as 5% to as much as 30% of corn acreage on each farm. (15,
16) The objective is to create a corn borer “refuge” from which a large number of susceptible
moths will emerge to mate with the non-susceptible individuals
that develop in Bt fields, thereby preventing or at least delaying
the development of resistance. (17) It is
unclear whether this strategy will work. (16)
If ECB strains resistant to Bt corn emerge, then commercial Bt
dusts and sprays would also be rendered largely ineffective, thereby
eliminating an environmentally friendly control option—one
which both organic and conventional farmers rely on. The use of
Bt corn and other genetically engineered crops is controversial,
especially in the sustainable and organic agriculture communities.
Damage to non-target organisms, including beneficial predatory
insects such as the lacewing (Chrysoperla spp.) has been documented; and concerns about natural gene transfer
to wild plant species is also a concern. (16,
18)
For the foreseeable future, Bt corn and other genetically engineered
varieties will not be permitted for certified organic production.
(19) Non-certified growers should do additional
research before selecting this option. For more information on
Bt corn and other genetically engineered crops, see the ATTRA
publication Genetic
Engineering of Crop Plants.
Corn Rootworm
The corn rootworm (Diabrotica spp.) is a beetle whose
larvae attack corn roots, reducing yield and causing stalks to blow
over easily (lodge) in high winds or heavy rains. Adults feed on
corn leaves and clip corn silks, thus inhibiting pollination.
There are three common species of corn rootworm. The northern (D.
barberi) and western (D. virgifera) rootworm species
are primarily pests of corn, though the larvae can survive on a
few other grass species. The southern corn rootworm (D. undecimpunctata),
also known as the spotted cucumber beetle, can attack more than
200 plant species including soybean, and is a major pest of cucurbits.
(5)
The females of the northern and western species lay eggs in late
summer, which overwinter to hatch the following spring. By contrast,
the southern variety overwinters in the adult form, hibernating
at the bases of plants and other shelters. They become active very
early in spring, with some of the adults migrating northward. Egg
laying begins roughly two weeks later. The larvae develop on the
root system of the host plant. There is usually only one generation
each year, but in the southern part of its range there may be two.
(5)
Cultural Controls
Crop rotation
has little or no effect on the southern corn rootworm because
it overwinters as an adult and has a varied diet. However, it
has been the most effective non-chemical means of controlling
the northern and western species until recently. There were reports
in the late 1980s from several northern states of northern corn
rootworm emerging in corn fields that followed soybeans in rotation.
This was the result of extended diapause—a phenomenon
in which rootworm eggs, which normally hatch the year after they
are laid, spend an additional year in the soil before hatching.
This delayed hatch effectively defeated the simple but highly
common corn-soybean-corn-soybean rotations used by many conventional
row-crop farmers in the region. (20)
The western corn rootworm has also developed means to overcome
the corn-soybean-corn-soybean rotation pattern. A strain of the
species has apparently evolved that “chooses” to lay
eggs in soybean fields under certain circumstances. One of these
circumstances appears to be the increasing number of early-maturing
corn varieties that the western corn rootworm adult finds less
attractive than still-succulent soybean fields. (21)
For crop rotation to be a successful tool in managing the northern
and western species, longer rotations, featuring greater crop
diversity (including forages, small grains, etc.) are becoming
necessary.
The southern corn rootworm can be controlled by late
planting, and by fall and early-spring plowing accompanied
by frequent cultivation to keep vegetation down. (5)
Sanitation to remove and destroy crop residues
also works to suppress the numbers of overwintering beetles (14),
though a heavy in-migration of egg-laying adults may counterbalance
any gains made.
Biological Controls
Populations of all three
rootworm species are suppressed by predatory ground and rove beetles,
Tachinid flies, Braconid wasps, mantids, spiders,
and parasitic nematodes. Like the beneficials that act to control
ECB, these are supported by farmscaping strategies
and reduced pesticide use.
Alternative Pesticides & Applications
Feeding
baits that attract and kill southern corn rootworm and
other cucumber beetles, developed through years of research, are
now available to commercial growers. Researchers determined that
buffalo gourd extract is a rich source of cucurbitacin. Adios™ contains buffalo gourd extract and carbaryl insecticide. Adios
AG™ contains buffalo gourd extract, floral volatile attractants,
and carbaryl insecticide. Note that carbaryl is a synthetic pesticide—often
marketed under the tradename Sevin™—and, therefore,
is not approved for certified organic production. However, the
effectiveness of the bait strategy is encouraging for the development
of materials (e.g., physical traps, botanicals, etc.) that could
be used by organic growers.
The larval stages of all Diabrotica species are susceptible
to attack by parasitic nematodes. The Rateavers
(22) recommend parasitic nematodes applied
three weeks after planting at 90,000 per lineal foot. Since most
nematode formulations are still rather costly, this practice would
be affordable only for high-value specialty corn crops.
Adult beetles can be controlled by sprays of the botanicals pyrethrin
or rotenone, or a combination of the two (14),
though their use would not be economical for standard field corn.
Monitoring
Strategies for rootworm management
are most effective and economical if some pest scouting is undertaken.
(This is often left to professional IPM scouts where conventional
pesticides are employed.) Cooperative Extension is a good source
of published materials to aid in identification of the different
species and for advice on when to begin scouting. Generally, scouting
can begin as soon as the crop begins to silk. Since adult rootworm
beetles feed on the silks, a tally is made by carefully approaching
an ear and counting all adults that are observed on or flying
away from it. The entire ear zone, as well as the point where
the ear joins the stem, should also be checked. Direct damage
to the silks should be noted. Sampling should be done on two ears
in each of 25 randomly selected locations in a field—a process
that should take about 45 minutes in a 40-acre field. Such checks
should be made weekly. (23)
If beetles have clipped the silks within a half-inch of the husks,
spraying to control the adults is often recommended under conventional
management to protect pollination. Rotation away from corn or
next-season soil treatment with insecticide is advised when beetle
populations reach .5 beetle per plant on first year corn or .75
beetle per plant on corn-after-corn. (23)
Finally, the presence of lodged corn in the characteristic “goose-neck”
curve is an indicator of rootworm problems in a field. However,
by the time such damage is apparent, it is far too late to do
anything for the “standing” crop.
Cutworms
There are several species of cutworms. Most overwinter as larvae
in “cells” in the soil, in crop residues, or in clumps
of grass. Feeding begins in spring and continues to early summer
when the larvae burrow more deeply into the soil to pupate. Adults
emerge from the soil one to eight weeks later, or sometimes overwinter.
Most species deposit eggs on stems or behind the leaf sheaths of
grasses and weeds. Eggs hatch from two days to two weeks later.
The worms are gray to dull-brownish in color; smooth-skinned; with
various markings depending on species. They readily curl into a
C-shape when disturbed. (24) They are known
to feed on nearly all non-woody plants, and are serious pests on
corn, onions, beans, cabbage, cotton, tomatoes, tobacco, and clover.
(5) Most species damage the crop by severing
the seedling at or just below the soil line, sometimes pulling the
plant into the ground as they feed. Climbing cutworms may sever
the seedling at higher levels and damage foliage.
Cultural Controls
Cutworms are a particular
problem in crops that follow sods, pastures, or weedy fields in
rotation. They are discouraged by clean tillage.
(5, 24) Clean tillage
to remove all weedy vegetation, at least ten days prior to planting,
reduces the number of cutworm larvae. Control of weedy
vegetation at field borders also reduces the number of
invading larvae. As with traditional cultural practices used to
suppress European corn borer, these methods are not consistent
with modern sustainable farming. They should be treated as transitional.
Biological Controls
Cutworm larvae have a number
of natural enemies. Predators include several species of ground
beetles. Parasitoids include tachinid flies and braconid wasps.
Cutworms may also be attacked by fungi, bacteria, and nematodes.
(25) As with other pests discussed, farmscaping
is a recommended means of increasing the numbers of beneficial
predators and parasites that help to keep cutworms under control.
Alternative Pesticides & Applications
Scout
for the presence of cutworm larvae early in the season, and after
destruction of adjacent habitats. Cutworms are best scouted at
night, when they are most active, using a flashlight. Look for
cut-off or damaged seedlings and dig around the base of the plant
to locate the larvae. (24)
Bait formulations (sometimes using bran) containing
Bacillus thuringiensis var. kurstaki have been known
to effectively control cutworm species when applied to the soil.
(14) Sprayed formulations may have variable
results with cutworms, as the worms may not ingest enough of the
toxin for it to be effective.
Research on the parasitic nematode species,
Steinernematidae carpocapsae, has shown it to be a very
successful control agent for cutworms. (26)
However, this option is probably too expensive for field corn
at the present time. It deserves mention because it may become
more available and economical in the near future.
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Disease Management
Fortunately, a good crop rotation and proper fertility management
appear to suppress many plant disease problems common to field-corn
production. For example, studies done in the late 1970s demonstrated
that Diplodia stalk rot was measurably less severe on organically
managed corn fields when compared with conventional production.
(27)
Varietal selection is also a key tool for addressing common diseases
in field corn. Since organic and conventional growers tend to select
the same corn varieties based on regional performance, they often
find resistance or tolerance to common pathogens already “bred
into” the cultivars they choose.
New tools for organic disease management are also becoming available.
For example, formulations of the beneficial fungus Trichoderma
harzianum (e.g., T-22™) are now available and can be
used to protect corn from infection by Pythium and Rhizoctonia
species that cause seedling diseases. (28)
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Economic and Marketing Considerations
Limited information has been developed on the economics of organic
crop production. The enclosed budget information from Rutgers University
is intended for the northeastern U.S. However, it is concise and
should serve as a starting point in determining production costs
elsewhere. Please note that two additional sources for budget information
are provided at the end of the Additional Resources
section of this publication.
It is important to consider organic production economics in light
of a whole-crop mix—a mix dictated in significant part by
rotation requirements. To assist in this planning, the Rutgers information
also includes information on organic soybean and alfalfa production—crops
that commonly rotate with corn in many production regions.
When estimating crop yields under organic management, many factors
need to be considered, including the current fertility status of
the soil, whether or not manure resources are available, and the
ability of the whole-farm ecosystem to provide natural, biological
pest control. The process of conversion to certified organic farming
can be challenging and disconcerting. ATTRA’s publication Applying the
Principles of Sustainable Farming does a good job of addressing
these concerns and is recommended.
In post-transition organic systems, experience has indicated that
organic corn yields are usually somewhat lower than those obtained
under conventional management. Soybean and legume hay yields appear
to be about comparable to conventional yields. Like corn yields,
small-grain yields are generally somewhat lower in organic systems
because of limited nitrogen availability. Often, however, organic
production costs are lower, compensating for revenues lost to yield
reduction, even when organic crops are marketed through conventional
channels. (27)
Market premiums are a significant motivating factor for transitioning
to organic production. Premiums for organic corn appear to average
about 20 to 50 percent above conventional prices, and have been
fairly stable historically. At present, the demand for organically
grown grains is increasing steadily. This should continue with new
markets opening for organic meat and the subsequent need for certified
organic feeds. While all this suggests that premium pricing should
also increase, the number of certified organic farmers is likewise
expanding. Future prices, therefore, cannot be predicted with any
accuracy and organic growers are well advised to keep production
costs modest. Historically, reduced production costs have allowed
organic producers to be competitive in conventional markets (27)
and organic producers continue to have the option of selling there.
Conventional growers, however, cannot access organic markets.
ATTRA’s Organic
Marketing Resources publication is a list of resources
to help you sell organic crops through established channels. Direct
Marketing is another ATTRA publication that deals with
marketing strategies that eliminate the “middle man”
by selling directly to the end user. Another ATTRA publication Marketing
Organic Grains also focuses on how to market food grains, oilseeds, and pulses.
Specialty Corns
In some circumstances, it is specialty corns, organically or conventionally
grown, that command the more attractive prices in the marketplace.
Among the better-known specialty corns are sweet corn and popcorn.
ATTRA’s publication Organic
Sweet Corn Production has already been mentioned. ATTRA
also has additional information on sustainable popcorn production
and marketing.
Other specialty corns include blue and white flour corns, decorative
“Indian” corns, baby corn, and cob corn, which is used
to make corn cob pipes. Many of these specialty corns—especially
those destined for food processors—should not be planted without
first securing a market. Such specialty grains are commonly grown
under contract and considerable market research should be done in
advance.
There is also interest in open-pollinated varieties of field and
sweet corn. An open-pollinated variety, in this context, refers
to a non-hybrid variety. The seed of open-pollinated varieties can
be saved for replanting to produce offspring similar to the parent
plants.
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References
- White, William C. and Collins,
Donald N., (eds.) 1976. The Fertilizer Handbook, 2nd ed. The Fertilizer
Institute, Washington, D.C. 208 p.
- Anon. 1993. Results in brief: Cover
crops and corn. Innovations. March. p. 2.
- Huhnke, Raymond L. 1982. Land Application
of Livestock Manure. OSU Extension Facts No. 1710. Oklahoma State
University, Stillwater, OK. 4 p.
- The National Organic Program. 2000.
National Organic Program; Final Rule. December 21. www.ams.usda.gov/nop/NOP/standards/FullRegTextOnly.html
- Metcalf, C.L., W.P. Flint, and
R.L. Metcalf. 1962. Destructive and Useful Insects, 4th ed. McGraw-Hill
Book Company, New York, NY. p. 490-493.
- Phelan, P.L., J.F. Mason, and B.R.
Skinner. 1995. Soil fertility management and host preference by
European corn borer, Ostrinia nubilalis (Hubner), on
Zea mays L.: A comparison of organic and conventional
chemical farming. Agriculture, Ecosystems and Environment. Vol.
56. p. 1-8.
- Based on the author’s personal
observations and data taken while on staff with the Center for
the Biology of Natural Systems, Washington University, St. Louis,
MO.
- Shirley, Christopher. 1992. Wasps
to the rescue. The New Farm. July-August. p. 38-39.
- Peterson, Dean. 1996. Field testing
biological insect control. The Farmer/Dakota Farmer. January.
p. 63.
- Bechman, Tom. 1989. Moths in
grass are cornborer tipoff. Prairie Farmer. April 4. p. 34.
- Lewis, Les. 1996/1997. Corn borer
control with the fungus Beauveria. Practical Farmer. Winter. p.
35-37.
- Lewis, Leslie. 1998. Fungal control
of corn borer—year two. The Practical Farmer. Summer. p.
27.
- Lewis, Leslie C., et al. 1996.
Aptness of insecticides (Bacillus thuringiensis and carbofuran)
with endophytic Beauveria bassiana, in suppressing larval
populations of the European corn borer. Agriculture, Ecosystems
and Environment. Vol. 57, No. 1. p. 27-34.
- Ellis, Barbara W. and Fern Marshall
Bradley. 1992. The Organic Gardener’s Handbook of Natural
Insect and Disease Control. Rodale Press, Emmaus, PA. 534 p.
- Byczynski, Lynn. 1998. Refuge
for corn borers. Growing for Market. December. p. 3.
- Hagedorn, Charles. 1999. The
Bt debate continues. Wisconsin Agriculturist. Mid- February. p.
34-35.
- Harlow, Susan. 1999. Why a 20%
Bt refuge is an IRM ‘must do.’ American Agriculturist.
March. p. 20.
- Anon. 1998. New evidence on Bt-corn
disputes companies’ claims of safety. Organic Farms, Folks
& Foods. September-October. p. 17.
- Shapiro, Laura. 1998. Is organic
better? Newsweek. June 1. p. 54-57.
- Swoboda, Rod. 1988. Counting corn
rootworms before they hatch. Prairie Farmer. December 6. p. 16.
- Holmberg, Mike. 1996. The drive
to survive. Successful Farming. May-June. p. 34-35.
- Rateaver, Bargyla and G. Rateaver.
1993. Organic Method Primer Update. The Rateavers, San Diego,
CA. p. 295-296.
- Pocock, John. 1994. Scout rootworm
beetles now to save on insecticide next spring. The Farmer. July.
p. 10.
- Flint, Mary Louise. 1990. Pests
of the Garden and Small Farm. University Of California, Oakland,
CA. 276 p.
- Hoffmann, Michael P., Curtis
H. Petzoldt, and Anne C. Frodsham. 1996. Integrated Pest Management
For Onions. Cornell University, Ithaca, NY. 78 p.
- Buhler, W.G. and T.J. Gibb. 1994.
Persistence of Steinernema carpocapsae and S. glaseri
(Rhabditida: Steinernematidae) as measured by their control of
black cutworm (Lepi- doptera: Noctuidae) larvae in bentgrass.
Journal of Economic Entomology. Vol. 87, No. 3. p. 638-642.
- Lockeretz, William, Georgia Shearer,
and Daniel Kohl. 1981. Organic farming in the Corn Belt. Science.
Vol. 211, No. 6. February. p. 540-547.
- Anon. 1997. T-22™ Planter
Box (product literature). BioWorks, Geneva, NY. 4 p.
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Enclosures
ATTRA Publication Sustainable
Corn & Soybean Production.
Anon. 1991. Non-chemical weed control for row crops. Sustainable
Farming News. September. p. 1-8.
Brumfield, Robin G. and Margaret F. Brennan. 1997. Organic Production
Practices: Northeastern United States.
Doll, Jerry and Larry Binning. 1991. Weed Management in Organic
Cropping Systems. University of Wisconsin, Madison, WI. 8 p.
Kruesi, W.K. No date. Organic Farming Fact Sheet No. 1: Weed Control
in Corn Fields. University of Vermont Extension, Woodstock, VT.
2 p.
Reznicek, Ed. 1992. Planning crop rotations. Sustainable Farming
News. April. p. 1-8.
Yanda, Bob. 1998. Eco-farming of corn for high yields & quality.
Acres USA. July. p. 16-18.
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Additional Resources
Dickerson, George, et al. 1992. A Small-Scale Agriculture Alternative:
Specialty Corns. USDA Office for Small-Scale Agriculture, Washington,
DC. June. 2 p.
Hoyt, Greg D. 1990. Choosing a legume cover crop for no-till corn.
p. 94-97. In: Mueller, J.P. and M.G. Wagger. 1990. Proceedings of
the 1990 Southern Region Conservation Tillage Conference, Raleigh,
NC. July 16-17. 107 p.
Sutton, P., et al. 1999. Pocket Guide to Field Corn IPM in the
Northeast, (IPM-1). Natural Resource, Agriculture, and Engineering
Service (NRAES), Ithaca, NY. January. 280 p.
Available for $7 plus shipping & handling from:
NRAES
152 Riley-Robb Hall
Ithaca, NY 14853-5701
607-255-7654
Swenson , Andrew, and Brad Brummond. 2003. Projected 2000 Organic
Crop Budgets South Central North Dakota, Section VI, Region 5. March.
www.ext.nodak.edu/extpubs/agecon/ecguides/2003org.pdf (PDF / 153 K)
http://web.aces.uiuc.edu/value/factsheets/corn/fact-organic-corn.htm
This Web site, prepared by the College of Agricultural, Consumer,
and Environmental Sciences at the University of Illinois at Urbana-Champaign,
features a “value-added calculator” and other budget
information for organic corn production. Practical production
details are also provided.
Organic Field Corn Production
By George Kuepper
NCAT Agriculture Specialist
Cole Loeffler, HTML Production
CT 113
Slot 7
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