Originally written February 1, 2006 | Last updated
October 23, 2015
Corn Grain Drydown
By early to mid October, dry-down rates will
usually drop to 1/2-3/4% per day (from rates of up to 1% per day in
September when drying conditions are usually more favorable). By late
October to early November, field dry down rates will usually drop to
1/4-1/2% per day and by mid November, probably 0-1/4% per day. By late
November, drying rates will be negligible.ber, probably 0-1/4% per day. By late
November, drying rates will be negligible.
Estimating dry down rates can also be considered in terms of Growing Degree
units (GDUs). Generally, it takes 30 GDU to lower grain moisture each point
from 30% down to 25%. Drying from 25-20% requires about 45 GDUs per point of
moisture. In October, we accumulate about 5-10 GDUs per day. However, note
that the above estimates are based on generalizations, and it is likely that
some hybrids vary from this pattern of drydown.
During a warm, dry fall, grain moisture
loss per day ranged from 0.76-0.92%. During a cool, wet fall, grain moisture
loss per day ranged from 0.32-0.35%. Grain moisture losses based on GDUs
ranged from 24-29 GDUs per percentage point of moisture (i.e., a loss of one
percentage point of grain moisture per 24-29 GDUs) under warm dry fall
conditions, whereas under cool wet fall conditions, moisture loss ranged
from 20-22 GDUs. The number of GUDs associated with grain moisture loss was
lower under cool, wet conditions than under warm, dry conditions.
Agronomists generally recommend that harvesting corn for dry grain storage
should begin at about 24-25% grain moisture. Allowing corn to field dry
below 20% risks yield losses from stalk lodging, ear rots, insect feeding
damage and wildlife damage. Be prepared for
localized root lodging and stalk lodging that may slow harvest and
contribute to yield losses.
Kernel Moisture Ranges (%)
- 33-40% Kernel moisture = Silage harvest
- 29-32% Kernel moisture = High Moisture Corn (High
Moisture Ear Corn and High Moisture Shelled Corn) - ensiled
- 25-26% Kernel moisture = Ideal fo < 20% Kernel moisture = field losses increase,
but cost of drying shell corn is reduced
Assess lodging potential
To assess lodging potential use either the pinch test or the push test to check for
stalk integrity. Conduct the pinch test by squeezing the second or third
internode above the ground. If it collapses, stalk quality is compromised. The push test is
performed by pushing a corn stalk to approximately 45 degree angle. If
it breaks, stalk quality has been reduced. If 10 percent of the stalks
tested show poor stalk quality or lodge at the root, then these fields
should be harvested earlier.
Use your time in combine
seat to scout fields
Harvest provides an opportunity to scout your fields. As you travel through the field, you can
observe various types of problems that may have occurred during the
growing season. Weeds that were not controlled would be one of the most
obvious problems that will show up. With the increase in weeds that are resistant to various herbicide
classes, it is important to identify these problems as early as possible
in order to control them as early as possible to control increases in
populations and movement of the weed. This may also provide some
opportunity to begin managing the problem this fall.
Insect and disease problems can also be detected in the fall. Note if
particular varieties seem more susceptible to an insect or disease. If one variety or hybrid seems to be more susceptible to disease
pressure or insect pressure, then this information could be used in
variety or hybrid selection for next year. If all hybrids or varieties
are affected similarly, then the cause of the problem needs to be
identified to aid in selecting management options for next years crop.
Read you operators manual thoroughly.
Read you operators manual thoroughly
for detailed settings
for you specific combine model. Attend combine clinics to learn fine-tuning
methods from other combine operators. With proper adjustment, a quality crop
can be harvested.
Corn Harvesting Losses
Ear droppage: One ear (3/4 pound each) in each 1/100 of an acre
is equivalent to one bushel per acre. To determine 1/100 of an acre,
take the normal 1/1,000 acre distance times ten. For example, in
30â€ rows, 1/1000 of an acre is 17â€™ 5â€; 1/100 acre would be that
distance across ten rows. For each ear in that area, there is one
bushel per acre loss.
Gathering Losses: grain that does not get into combine
Improper adjustment of threshing, separating and
loss is indicated by kernels attached to pieces of cob behind the
combine. These were not shelled by the rotor or cylinder.
losses are additional loose kernels on the ground behind the combine.
These were not shaken out of the cobs and husks and were lost over the
back of the separator.
How to Measure Losses
Determine average loose kernel loss and cylinder/rotor
every 2 kernels per square foot = 1 bushel per
Kernel still attached to cob = cylinder/rotor loss
Acceptable level = 1.2 to 3 kernels per square foot
Determine machine ear loss
Behind combine, gather all ears on 1/100 acre
In front of combine, determine pre-harvest ear loss
in standing corn on 1/100 acre
Subtract pre-harvest ear loss from ear loss at the
rear of machine
each 3/4 pound ear = 1 bushel per acre
each 1/2 pound ear = 2/3 bushel per acre
Acceptable level = 0 to 1.0 bushels per acre
Typical level = 0.6 to 2.5 bushels per acre: Can you limit
your total field loss to less than a half bushel per acre?
That would place you and your combine in the top ten percent.
Test Weight versus Yield
The formula used to determining corn yield is ([100-%moisture] X weight
of grain X 109.815 divided by length of row divided by width of harvest
swath in inches).
This formula does not consider test weight. Why? Because test weight is
not a yield component, it is a volumetric measurement and is not indicative
of how much weight in pounds comes off a given area of land. The â€œweightâ€ in
units of pounds is used as the basis for payment of grain. By law a bushel
of corn weighs exactly 56 pounds. The weight of grain sold (bushels) is
calculated by dividing total weight in pounds by 56 lbs/bushel. No. 1 yellow
corn is 56 lbs/bu; No. 2 yellow corn is 54 lbs/bu.
The price a seller receives for grain can be influenced by test weight.
For example, grain graders will discount $0.01 per bushel for each lb/bu
between 54 and 52 lb/bu; $0.02 per bushel for each below 52 to 50lb/bu and
$0.03 per bushel below 50 lbs/bu.
High yielding hybrids can be a high test weight hybrid or a low test
weight hybrid. There are a number of factors that influence test weight,
genetics, kernel size, density, shape and stickiness. Kernels that are
slippery pack better. Wet corn is sticky and does not pack well.