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Corn Lodging
No one likes lodged corn. Often
yields are reduced with harvest slow and stressful. In addition, volunteer
corn can be a problem the following crop year. Lodged corn doesn't happen
all of a sudden in the fall, many factors throughout the growing season
contribute to lodging. The decisions you make and the management steps
you take before planting and during the growing season can significantly
influence whether your corn will or will not be standing at harvest.
Crop Rotation Program:
A sound crop rotation program helps reduce the risks of leaf diseases
and rootworm larvae populations. For continuous corn production, a rootworm
insecticide or control of the adult CRW beetles is recommended. Follow
the chemical label and apply the recommended rate for control. Rotating
insecticides will lessen the chance for insect resistance and in the case
of soil applied pesticides, restrict the buildup of soil organisms that
speed insecticide breakdown. Leaf diseases reduce the amount of photosynthesis
taking place during grain fill. Any reduction in photosynthesis will cause
a sugar imbalance between the ear and the stalk. Such imbalances lead
to weak stalks.
Tillage System: Reduced
or no-till systems favor leaf diseases more than deep tillage. Residues
in the field serve as a source of inoculum for many of the leaf disease
organisms. Incorporating the stalks in the fall helps decrease the survival
of disease organisms and lowers the risks of leaf disease and lodging
problems in future corn crops. With reduced tillage, potassium generally
is less available and an application of extra potash may be needed to
improve standability. On the other hand, when residue is removed or disturbed,
the soil can become hot and dry which restricts secondary root development.
Field Selection:
Leaf diseases tend to be a bigger problem with pivot irrigation or in
lowland areas such as in valleys, between ridges or along streams and
rivers. Also, soils that tend to be wet, favor infection by the root-rotting
fungi which often spreads to the stalk.
Soil Fertility:
Avoid excessive nitrogen applications and raise potassium levels accordingly,
especially if corn follows alfalfa. Adequate potassium is very essential
for sturdy stalks. Applying fertilizer near the row at planting should
boost soil maintenance levels of potash under no-till and avoid a possible
nitrogen-potassium imbalance. Research has shown that potassium fertilization
can reduce lodging on medium to low testing soils. Proper fertilization
with adequate levels of all nutrients is important for good crop management.
Hybrid Selection:
Hybrids vary in their genetic ability to tolerate or resist major leaf
diseases and stalk rot organisms. Take this into consideration when selecting
the hybrids to plant on higher risk fields. In addition, hybrids vary
in stalk strength and rind thickness, those having the highest yield potential
also tend to have weaker stalks. Match hybrids to your expected harvest
date based on planting and maturity. Early hybrids generally suffer more
stalk rot especially if harvest is delayed.
Planting Time Decisions:
Avoid excessive population rates for your fields and fertility
levels. Corn planted early can tolerate higher planting rates, but is
more likely to be infested with first generation European corn borer which
predisposes plants to lodging. Corn planted late grows taller with smaller
stalks, increasing the odds of standability problems. In addition, late
planting may result in a delayed harvest with late-season weather problems.
During wet seasons, planting
depths often are adjusted for shallow seed placement. As a result, seed
which may not be planted deep enough is improperly covered with soil which
results in poor seed to soil contact. Later rains may add to the problem
by washing soil away from around the germinating seed. Shallow planting
can cause nodal roots to develop on or near the soil surface. Also, wet
soils are good breeding grounds for stalk rot organisms. This is the start
of root problems.
Emergence Period:
Heavy rains after planting can wash or leach soil rootworm insecticides
out of the effective zone or hasten insecticide degradation. In contrast,
periods of excessively dry weather can limit activation of rootworm insecticides
and result in marginal insect control. Erosion and wet soils can cause
spindly, weak roots or the rootless corn syndrome. Affected plants may
lodge later in the season if there is a strong wind. Root pruning injury
due to cultivation or applications of 2,4-D/dicamba products during periods
of high temperatures and high humidity, which often makes corn stalks
brittle, can lead to increased lodging or stalk breakage problems.
Vegetative Period: The
potential for ear size and number of kernels is being developed during
this stage of growth. High winds along with hard rains and wet soils can
cause root lodging because brace roots are not fully developed at this
stage. Severe gooseneck can cause permanent damage and reduce grain yields.
All hybrids are susceptible to green-snap from knee-high to tassel.
Grainfill Period: Large
amounts of sugars are needed to maintain stalk quality and feed the developing
ear during this period. Favorable conditions will contribute to a large
ear with lots of room for kernels. If the plant suffers from environmental
or nutritional stress during the grain-fill period, a sugar imbalance
may result between the ear and the stalk during grain-fill. Leaf loss
from hail, insects or diseases during this period reduces the ability
of the plant to make sugars for the ear. Any restriction in the production
or movement of sugars will speed up plant death in the roots and stalk.
This death then gives stalk rot organisms the chance to do their job.
Cloudy weather, early frost, leaf diseases, high yield potential, are
among the many factors that may restrict or compete for plant sugars.
This sugar imbalance may account for much of the variability in lodging
seen between or within a field.
Maturity: Harvest-time
weather has a strong influence on lodging. Temperature, rain, snow and
wind all play important roles. It influences the rate of stalk degradation
and can dictate when you get into the fields to harvest. Regular inspections
of fields to check stalk and root health as well as grain moisture will
help you decide field harvest order.
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